How to: Freshen your 200-4r pump

[Ineedagn]

NOTE: You MUST be logged in to see pictures in this thread.   Signing up is easy.   I had no way around it.


PREFACE: THIS INFORMATION IS NOT INTENDED TO BE TAKEN AS GOSPEL.  THIS IS ONE PERSON'S WAY OF DOING THINGS, SOME WILL DISAGREE WITH SOME OF IT, I'LL TRY TO POINT OUT ANYTHING THAT FALLS UNDER BUILDER PREFERENCE. None of this will be news to any of the veteran builders, but I'm doing this by request to help the average "guy in his garage" get his pump built as properly as can be done without machining the housings. I got good at these back when I worked full time at a trans shop doing 700r4 pumps. Thankfully for us, most parts interchange except the housings themselves, which greatly helps part availability and cost. Let's not forget that the 200-4r predated the 700r4 by three years, so the early build 200s are GM's first use of this style pump. which brings me to the first area of discussion.

What pump castings do you have and what's the difference? Early build pumps and pump covers are 149/150 casting number (ignore the red paint,it's the only early pump I have here), late castings are 082 body/088 cover and then the latest 690 body which used the same 088 cover. Here's the differences:

Early style is the bottom housing in this picture. The cavity that the orange screwdriver is stuck into is line pressure. Note how the early casting has the top land of the pressure regulator valve open for line pressure to exert force on it and uses a solid valve, and the late casting has the top of the valve area closed off. Now note how the late pr valve has a hole in it, EDIT: crap, you can't see the hole in this pic. Anyway, the late pr valve has a hole in it that goes from the area of the 90 degree pick, up through the valve and out the top of the valve into the now sealed off cavity. Still gets the same line pressure to the top of the valve, just through a different route. There's a GM service bulletin on the change, it was done to help isolate the land from pump pulsing in an effort to reduce PR valve buzz. I HAVE read mixed impressions about it's effectiveness. Some claim they won't use early pumps and some claim there's no practical difference. You do, however, need to know about this for interchange reasons. The "proper" way to do it is to use the 149/150 early combo as an assembly with the solid PR valve and use the late 082 or 690 body with the late 088 cover with the PR valve that has a hole through it. However, the only combo that absolutely won't work is to somehow end up with an early solid PR valve in a late housing. If you mix/match the parts it'll work as long as you have a pr valve with a hole in it. However, it'll work the same as an early design with line pressure acting directly on top of the valve and not through the hole.


Next pic shows the early and late pump bodies with the tools pointed at the same holes as the cover in the previous pic. Note how the late casting was revised with a larger flat machined area to fully isolate the valve tip from line pressure and forcing it to go through the hole in the revised valve. If you use an early body with the late cover it will allow line pressure to go around the newly sealed off cavity and negate any gains from the design change. It WILL "work", however.


Next pic is of the pr valve circuit from the manual. My manual only shows the early design, not sure if a later revision bothers to show the late design?? Edit:  It doesn't.

Again, if anyone has more detailed info or testimonial from using early vs late pump castings, I'm all ears.

[Ineedagn]

Teardown: Remove the 5 bolts that hold the two halves together, set the stator side of the pump aside and start on the pump body. Remove the top ring, the rotor and vanes, and rotor guide. Pry the spring(s) out from the slide with a rag over them to keep them from flying off. For some reason I forgot to take pics of all of this :red face: but i assume you have a manual of some sort if this is the first time you've been in one of these anyway. Remove the slide, pivot pin and pay special attention not to lose the little spring under the pivot pin.

Now take a screwdriver and hammer and pry out the old seal: (I'm using the red pump only because I've already removed the bushing and seal from the one I'll be building).

Using a bushing driver, remove the bushing. If you have a 690 pump body, you will have to remove it by driving it "inward" because the 690 pump body has a ridge in it to prevent the bushing from walking out. You can remove this with a screwdriver or chisel (carefully) but you'll want the proper driver to reinstall it anyway. Mine's custom made just for this bushing, I haven't looked but I'm sure they are commercially available.

[Ineedagn]

Next two pics will show the difference in seal area. 149 and 082 are identical here. 690 has the aforementioned step as well as a bit more relief for seal drainback.


 Bruce from PTS was an avid believer that the earlier bodies needed to be milled out here a bit to match the 690s profile for a drainback aide. I doubt it makes any difference in reality but just for fun I'll include a pic of one of my adventures doing the same thing in redneck fashion:

 don't recommend that "mod" I just inserted it for comic relief. Though I did put that in a trans....

[Ineedagn]

Inspect the pump vanes where they contact the rings. If theres a visible notch in them, replace them (same as 700 and cheap). You can reuse them if they're not worn. Pic of an acceptable one vs a worn one (and they can be much worse than this):

Now, take the original pump rings, clamp them in a vise and snap them in half:

This is done to A: illustrate how brittle they are and B: keep you from ever reusing them. We will be replacing them later. (note: if its been apart it may have better rings in it already and they may be harder to snap or impossible. Replace them anyway so you know what you have. More on that later)

Plastic rotor guide: Gently try to flex it. If it's not brittle it can be reused, but honestly, they're like $1. Be sure you're getting a 7 vane guide when you purchase.


Obviously inspect the rotor and slide for any cracks or obvious wear, on the rotor make sure you inspect the tabs where the converter engages it. Now back to the pump cover (stator side).

[Ineedagn]

Take a snap ring pliers and remove the PR valvetrain, starting with the boost valves. They are spring loaded, so a couple gentle pushes on it usually gets them to pop out. If they are stuck you can gently (and carefully) pry on the pr valve to help force them out. Just don't damage any valve lands or the machined surface of the housing. I'm including pics of the lands you measure to determine the size of the boost valves. This pump is out of a BRF core so it has factory .471/.265 valves. Note the hole in the PR valve as mentioned earlier.

Looking at the next pic, the orange screwdriver is pointing to a land on the PR valve. Sometimes this land gets modified with flat spots ground into it or ground completely flush with the stem of the valve. The details of this get pretty technical so i'll try to be concise but I doubt I succeed, because the actual position of this valve under WOT will change depending on line pressure and boost valve and spring combos.  This land has the possibility (but not guaranteed) to restrict and then cut off converter charge/cooler/lube flow under heavy throttle, which preserves pump volume and limits converter charge pressure. This modification is one of the big items falling under builder preference.  Transgo kits have you grind this land all the way off.  This may be beneficial in your 700r4 if you're towing a heavy load up a mountain with an underpowered TBI 305 in your 91 chevy pickup.  Most people reading this, arent doing that.  In fact, very few people with 700r4s are still doing that 30 years after the fact.  Understand that there's a difference in usage between a truck towing a load with your foot heavy into the throttle for long periods (and with a lower max pressure) and brief full throttle acceleration in a car (with max pressures of 260+).  Here's some math for you to digest: The outer diameter of the land is .365" and the stem diamter is .260".  If you grind it perfectly flush, the area difference is about .0516 square inches, which is slightly bigger than the area of a 1/4" drilled hole.  A LOT of fluid can pass through that big of an opening at full boogie pressures north of 260 PSI.  Enough fluid, in fact, to create a serious converter charge pressure issue if your transmission cooler circuit doesn't flow well enough to deal with it all.  There's a large number of aftermarket radiators, trans coolers and fittings on the market that can cause a back pressure issue that will overload the engine thrust bearing in this scenario.  Personally I'll never send one out the door with that land ground completely off, but there may be some merit to grinding SOME material off of that land.  Once you get to max line pressure, the blowoff spring and ball are going to exhaust some fluid anyway and letting it go through the lube circuit instead of the blowoff circuit could be beneficial.  GM eventually came to this conclusion as well, as they had a revised valve in the 1993 model year 700r4 (last year for 700 and only in certain models) that had a flat spot cut into this land.  GM part number 8684048 is the valve in question.  Long since discontinued, if anyone has one i'd appreciate you measuring the flat in the valve just to satisfy my curiosity.  So what should you, the home builder, do with this valve land?  That's the million dollar question and every builder will likely give you a different answer.  I can tell you that as of this writing (and re-writing), every one I've ever sent out the door had an unmodified PR valve.  Unmodified valves are drying up, however.  Superior makes an "upgraded" PR valve, i ordered one, side by side with the OEM valve there's a bunch of small changes that I don't blindly trust, as of this writing I can't recommend using it.  If I ever get around to testing it (or any other PR valve mods) I'll update this section (don't hold your breath). In rare cases the top land of the valve may have a flat ground on it. It's a transgo "fix" for the wrong pr valve/pump casting mismatch. If the top land has been touched, definitely replace the valve with one that has an unmodified top land and double check your pump casting/PR valve style combination as mentioned in the first post. 700r4 valvetrain is identical and I also believe the Sonnax reamer and oversized pr valve from the 700 can be used if the bore is worn or you're that desperate for an unmodified valve. Be warned the increased valve diameter of the reamed valve setup will alter the force applied by line pressure on the top land and can affect your pressure rise. Someone correct me if I got any of this wrong.  I'm never too old to learn. 

[Ineedagn]

Remove the lockup valvetrain as shown. Then remove the pump relief spring pin, spring, and ball. It's a stiff spring so it's a good idea to cover it with a rag when you remove the pin. If there's a filter o-ring still in the housing, carefully pry it out without scratching the bore. If the bore is gouged from a previous filter change, now is a good time to smooth it out with fine sandpaper.

[Ineedagn]

Remove the T27 screws holding the stator tube to the housing. If they become stripped you can grind a slot for a large flat tip screwdriver or grind it off completely and remove it after the tube is pressed out. PRESS the tube out using a hydraulic press (not a hammer), placing the supports as close to the center of the housing as possible while still allowing the tube to press out. Middle pic is a comparison of the original tube (note the wear on the splines) and a hardened tube. Hardened tube is cheap and should be done in every build, every time regardless of the condition of the original splines. If the pump has been apart before, it may have a hardened tube in it already. You can leave it in if the machined face of the aluminum housing doesn't need any work to it.

[Ineedagn]

So at this point, you should have two bare housings. Start by enlarging the 3 drainback holes in the pictures below. This relieves pressure on the seal and prevents the seal from leaking or blowing out of the pump body. There's a little bit of debate here, some claim there's no benefit to it, I've seen plenty of evidence that there's merit to doing it.  I'll leave it at that.  Besides, it's FREE to do! 

The two holes in the body are obvious, but don't forget the mating hole in the cover.

Don't be a hero, enlarge them one or two drill sizes at a time and it'll go a lot smoother. Go to at least 1/4". 9/32" or even 5/16" is better IF you trust yourself to do it and it appears safe to do so, meaning if the passages are already drilled somewhat crooked and you think you'll break through by going bigger, use your noggin and stop while you're ahead!  Chuck the drill bit out toward the edge of the chuck to make it longer and easier. Use the intersecting hole as a visual guide that you've drilled it far enough.

Using a countersink or a deburring tool, make sure the holes are deburred well. This is especially important on the two surfaces that mate together with no gasket. If they aren't perfectly flat, you'll cause the whole pump to crossleak.

[Ineedagn]

Now we deal with the machined surfaces of the housings. There's no gasket here, so if these surfaces aren't perfectly flat, you'll have cross leaks. From the factory there are areas where the housings aren't flat due to GM staking the cup plugs in, If you check these against the opposing housing you'll notice they fall into a cavity and not the flat machined areas. They won't cause any problems if you have to leave them alone. Second pic is of random damage caused by the housings being mishandled after machining when they were new. If you can't flat sand the housings, you need to at least inspect them closely for this kind of stuff (on all surfaces) and use a whetstone to true it up if necessary.

Now, I happen to have a pair of granite surface plates with sandpaper on them for flat sanding. I realize most people who would actually use this tutorial don't have access to this and must use a whetstone on a nice housing to get by with. You should look into a cheap 9x12x2 granite surface plate though, they're pretty cheap and even the cheapest ones out there are flatter than they need to be for sandpaper. 9x12 accepts any old store bought sandpaper grit and comes in handy for flat sanding everything engine/trans related. I have a fine grit and coarse in 18x24. On the pump housing side, I just hit it quick and look for the sanding marks to be even all the way across, indicating it's flat. Occasionally I'll see raised areas around the bolt holes that need a little sanding to flatten out. I don't know if this is caused by overtorquing or overheating or but it's something to keep an eye out for. I hit this at the bare minimum because I don't want to change the dimension of the pocket depth, I'm just verifying flatness.

The next pic shows the wear on the cover side housing that I'm going to sand out. As long as I turn the housing often as I sand it, I can sand out a lot of wear here with no concern for dimension change as it will stay parallel to the back side surface. First pic is a straight edge with a flashlight behind it showing the groove from the rotor. Second pic shows the wear from the slide as well as the rotor and vane marks. This pump was out of a pretty damn decent trans, yours will likely look the same or worse.

[Ineedagn]

I ran it on the fine paper just once or twice to highlight any high spots for pictures. This shows the staked plugs and how much aluminum is raised by them. Third picture is interesting. Remember the drainback holes I enlarged and deburred? Yeah, that still wasn't flat. If you can't flat sand your housings, be DAMN SURE those two mating areas are flat. Whetstone or equivalent method. The drill bit raises more aluminum than you can see with the naked eye.

Sanding my arms off...and a midway progress pic...

ALL DONE! If you look closely you can see I didn't get the deepest groove completely out, but the slide marks are gone and the groove won't catch a fingernail anymore.

[Ineedagn]

Now it's time to notch the housing so I can stake the bushing in it. Using a round file, cut two angled grooves opposing each other. You can do it without cutting into the rotor guide area, I let this one dig in a little on purpose to illustrate that it makes no difference if you do as long as its deburred. Note the notches don't go all the way down the bore, we don't want to take away any more surface contact area than we have to. *Some builders won't bother to notch/stake a 690 pump body due to the step in the front being able to hold the bushing.  Other's won't stake any of their pump bushings.  I stake every bushing out of habit, from the old 700 days. Here's a fine time to mention that I've seen a couple of the 082 pump bodies that had the step in them just like the 690, although it wasn't as pronounced. One of them is now in "usetaboost's" car.

I'm not installing the bushing yet, but I notched it now because I wanted it done before I "hand lap" the pump cavity. *This is another area of builder preference.  Some builders won't touch the pump cavity.  Some reading this won't trust themselves to do it either.  It'll work just fine if you don't.  400 grit sandpaper from a roll is perfect for this, it will break the glaze and remove minor marks without changing the dimension easily. 600 would work and might be better for a novice, I would think it to be damn near impossible to screw it up with 600 grit. I use a few drops of trans fluid or penetrating oil so the paper doesn't clog up, and then use my thumb in a repetitive circular motion while turning the housing (yes, I'm left handed). First trip around the housing, I scoot my thumb up the roll often, keeping fresh paper under it. Second trip around, I leave the "dead" paper under my thumb for a smoother finish. This was something I got good at in the 700 days and is second nature to me now. Just try to get all the way to the outside of the cavity and sand it as evenly as you can.

You can't see it well in the above pic, but when rotating the housing in the light I can still see traces of the original rotor marks. This tells me I didn't change the pocket depth. This is done for the same reason you break any glaze in an engine or trans and the reason you crosshatch a cylinder: Oil retention. Most used pumps will still show a groove or two after sanding this pocket. As long as they aren't severe they won't hurt anything or cost you any max pressure.

[Ineedagn]

Now I surface the rotor and slide. I start with the slide ring, leaving it in the slide with the old o ring under it. On this pump I did a quick rub on the fine grit stone because my 280 is about dead. If it was a new sheet I might hit it on the 9x12 stone with some dead 320 or finer after the 280. I really doubt it matters much, again, this is just how "I" do things.

Now I remove the ring and surface both sides of the slide and rotor....note the marks on the top side of the slide aren't completely gone. They won't hurt anything. I might be able to sand them out but it would likely alter the slide clearance in the cavity by the time they were gone. Also should note: DO NOT try to sand the inner surface of the slide where the pump vanes rotate. The slide is treated with a process called Parkerizing, which is an anti-wear coating and even if it has some wear showing, you'll do more harm than good by sanding on it. If most of this coating is gone you should consider slide replacement.

[Ineedagn]

Now I'll give the parts a quick spray and check clearance with plastigauge. A strip of plastigauge is literally $2 at the local parts store, go get a strip and use it. I use three small strips of plastigauge on both the slide (without seal) and rotor, then torque the cover on at 18 ft lbs. This one ended up right at .002. Perfect. Steve V and Richard Clark have an alternate method of checking clearance and Steve can chime in with it if he wants to share it.

I checked it with a straight edge and a feeler gauge which loosely verified the plastigauge. 1.5 thou barely fits under it in most spots and a .002 doesn't quite fit, but if I lift the straight edge to place it under it, it doesn't have any wobble to it when set on the .002.  Ideal pump clearance is between .001 and .002. For your average garage build, the slide can be quite a bit looser than that (.003 or more) because it has a positive seal under it. I've let the rotor be .0025 or so before and never had any issues with pressure loss. I've always wanted to assemble a "loosey-goosey" pump and see how it affected pressure but never have, mostly since I have the ability to get it right. Maybe others will chime in with more data on pump clearance vs. consequences. I do know if the slide is too tight it will bind in the housing, the rotor would probably "self clearance" if it doesn't break first.

[Ineedagn]

Now that we have the parts all surfaced and clearance checked, we can start the assembly. Spray both housings thoroughly with brake clean and blow dry with compressed air. Let's start with the pump cover/stator support.


Grab the old stator support and chuck it in a vise. Use an .045 drill to enlarge the orifice in this cup plug inside the alignment pin. This increases lube oil to the "mickey mouse" washer behind the pump. In the event you can't enlarge this, at least verify that it's not obstructed and that it was punched cleanly from the factory. Note about this cup plug: Not all of them are staked into the pin from the factory. I have seen one fall out (was wedged sideways in the washer upon disassembly). The pin is hardened and does not deform easily, so it is difficult to stake/peen the opening to prevent this.  If it's not staked, at least verify the cup plug is seated well.  Next pic is showing me removing the pin from the old stator support with a punch.

Tap the pin into the new stator tube, use something with a 90 degree angle to "eyeball" that the pin is straight in the flange and parallel with the tube. PRESS the tube into the housing (Again, no hammer) making sure the support plates under the housing are positioned as close to the center as you can while still allowing the tube to pass between them. A couple grease rags are a good idea to protect your freshly sanded face from damage.  If you're a novice and this task gives you fits/makes you nervous, you can place the stator tube in the freezer for a while and set the housing somewhere warm like on top of a heated parts washer and it will slide in easier. Just keep an eye on the pin orientation on the way in. Clean the bolts and threads in the housing with brake clean and blow dry. Apply a single drop of red locktite to the bolt threads, torque the bolts to 10 ft. lbs. If the original bolts are damaged or if you have difficulty with the torx head, you can replace them with an ordinary M6x1.0 thread hex head bolt, just check the fit of the mickey mouse washer.  I'll reiterate: CHECK THE FIT OF THE MICKEY MOUSE WASHER if replacing the screws. Shortly after writing this the first time, I helped a guy diagnose a front end play issue that was tracked down to the bolts he was using here. 

The stator tube pin is hardened, but the tube flange itself is pretty soft metal and can easily be staked with a punch to hold the pin from walking out against the washer. Pin can't really go anywhere except against the mickey mouse washer once its assembled, I stake it anyway. >BEATING THE HELL OUT OF THE PIN ONCE IT'S ASSEMBLED COULD BREAK THE HOUSING BY FORCING IT THROUGH THE BOTTOM OF THE ALUMINUM BORE. IF YOU DOUBT YOUR ABILITY, DON'T STAKE EITHER THE PIN OR THE CUP PLUG INSIDE THE PIN. IN FACT, FORGET I EVEN MENTIONED IT (LOL). <

insert forgotten pic here

[Ineedagn]

One problem that happens with high pressure pumps, is that when we make enough pressure for the pressure release valve (blowoff valve) to open, it can cause the spring to start breaking 1/2 coils off where it rests against the narrow pin. This reduces spring pressure and makes the ball open early, causing low max pressure and/or pump buzzing. To solve this, insert a hardened washer between the pin and the spring. An easy source for a washer is to get an extra lockup valvetrain washer from another pump or your local trans shop (same as 700), it measures .040 thick. I use a stainless steel washer that measures .060, I only do this because I have a whole stack of this washer here with no other use for them. I wouldn't trust a mild steel washer here (use the lockup washer). I'd like to publicly thank Dave Husek for this tip after I had this issue with the very first 200-4r I ever built with performance in mind. Couple of the vendors carry a better spring that also raises the blowoff pressure from ~260-270 to over 300 psi.

Clean, lube, and insert the lockup valvetrain as it was removed, making sure the snap ring is properly seated and that you can move the valve by pushing it with a small screwdriver through the hole. If you are building a non-lockup trans, replace this valve train with a non lock up kit and use their instructions. One area I have no experience with is with the very early/diesel/export transmissions that have a hydraulic lockup valve in the valve body. I don't have any of that here so I don't know if any of this valvetrain is different. If someone else has this info please post it here.

Here's the part where I would normally install the Pressure regulator valvetrain and boost valves, but apparently I forgot to order the damn things. For anything that resembles a performance build, use an aftermarket PR spring, either the one that comes with your shift kit, or order the purple TCI spring from summit or jegs, OR if you're going super low budget and don't have the $11 plus shipping, walk into any trans shop and ask for a transgo green PR spring. They probably have a pile of them laying around (again, same as 700r4). ANY performance oriented spring will be better than stock, I believe the purple TCI will give the highest base pressure but I'll confess I haven't done any back to back testing.

On the subject of shift kits, I highly recommend a kit from a known 200 guru. I strongly DON'T recommend the green box transgo “noyoyo” kit intended for  ordinary passenger car use, especially the "bootstrap" tv plunger/valve setup. It's the exact opposite of performance and even transgo knows that, because they don't use that in their HD2 performance kits.   Also along this topic, you’ll hear me reference a max pressure of 260+.   This write up will allow the pump to be capable of making that pressure and survive while doing it.  The actual max pressure and pressure curve is dependent upon your shift kit calibrations and carb/throttle geometry and that’s far beyond the scope of this write up.  Can’t stress enough that you should support the known gurus for your complete shift kit, tailored to your specific needs.   Sorry for the derailment from pump tech.

Boost valves: .500 main boost valve is cheap, effective, and available everywhere. Larger ones exist but the .500 will be ideal for anything built by anyone actually following this thread (garage hobbyist). Reverse boost valve: if you've got the largest factory one (one pictured above) it's fine for any garage build. Larger valve here only gives you additional pressure boost in manual 1 and manual 2. Some aftermarket boost valves have O-rings on the outside for better sealing in the bore, it's builder preference though. The non o-ring factory style works fine. Most of the valves are kind of hangy when new and I end up polishing the valve. You can also polish the PR valve and lockup valve if they're scored up, just use fine sandpaper (400-600ish).