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How to: Freshen your 200-4r pump

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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. 

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