Tony

In the process of cleaning putting my valve body back together. And when i post pics later hopefully this will be a good guide for someones future reference.

As far as i know i have just about every MB and Misc transmission manual i can find, however, none of them are specific to our application(porsche). Unless i missed it, even the shop manuals don't describe in detail the components of the valve body and the assembly in OUR cars.

Every parts diagram i see is just slightly different from the next and from what is actually in the valve body. I can see that rebuilding a valve body is one of those items that you either get right or you dont, PERIOD. I want to get it right the first time.

Is there an image or diagram out there that shows the valve body pistons..orientation etc that is specific to our car(specifically 87s4 for example)?

In short... I have one piston assembly that when "assembled" with the spring, is too long. The spring is at full compression and the side plate will not go on. It just doesnt "feel" right either. One of the pistons in that assemly(see pics) is "hollow" on one end and even with the spring inside that it does not fit

I was pretty surgical laying out and organizing my parts but now my "faith" has been shattered a bit.

Bill Ball

Those parts do not look at all like the ones you have circled in the diagram. For example, where's part 18?

Glen McCartney

Tony, I feel your pain, that is what held me up from finishing my trans rebuild. The 928 manual has nothing on the layout of the parts in the valve body and as I found out the documentation I had was different from what was in my valve body. Plus, one valve fell out when I wasn't looking, thought I got it right, but when I finished up the trans I had issues. It shifted fine from 1st to 2nd to 3rd and then 4th but then was hunting between 20 and 40mph, there were all kinds of other problems, like trans is in 1st gear when neutral is selected, reverse was actually locked up. I had to ship my valve body to an expert, who has other valve bodies to re-configure mine, including devices to measure spring tensions. Hope he gets to it soon.

The spring in the piece you show looks longer than diagram. Part 18, in mine, was a sleeve in the valve body, probably still in your valve body.

Bill Ball

Here's another diagram. It looks like you have parts 7 and 5 with a spring. Could the spring be mixed up with one in the valves next to the one in question? I agree, you are amazingly well organized, far more than I am, and devise a part sort system that seems would assure you have things correct.

Glen McCartney

Any chance the spring is not fully seating inside the valve body?

Tony

part 18 is a sleeve..its inside the bore.

and for example..that spring above part#3 in your SECOND image wasnt present in mine. That part#3 is one of those that get stuck in the bore with the residual fluid. When you think you have things all apart you turn it over and it falls out...doesnt it Glen!!

At least its all cleaned up, its actually the cleanest part on my car ...its no trouble working on it at the kitchen table now over a cookie pan.. Im going to take it all apart again and double check things. I have that diagram you show above and hopefully it is to scale and i can cross check spring size/diamter. Short of taking my OTHER valve body out, that about all have to go on.

Glen McCartney

That spring wasn't in mine either, Greg Brown said it was in later years. Yup it does get stuck and even if you think you put it in right......

Bill Ball

Agreed, the spring in part #3 is not present in our trannies, as Glen found below.

https://rennlist.com/forums/928-foru...-mr-brown.html

Leon Speed

I am so not taking that thing apart.

Tony

Once I get some picture up it will be a snap. I want to make sure they are correct first.

Glen McCartney

Tony, the picture below shows about how far out the valves were when to cover is removed and the spring tension pushed the valves out.

Tony

Thnx Glen, I have it figured out..but that picture helped with the conclusion. Some how a spring got swapped one side to the other. I went through the manual and the pic posted by Bill above (that I have also) and compared the relative length and diameter of the springs on each piston. There was a glaring difference between the spring on piston 16 and the one on 17 as far as length(see below) When I swapped them back, everything fits nicely and the piston protrudes just as shown in your picture above and the other one fits with the end plate on(it didn't before)
When you look at the pic below, it jumps out at you easy..but when you are actually trying to pick out something that doesnt match its tough! Its like one of those puzzles where you have to pick out the difference between two VERY similar images.

Thnx.

Feeeling much better now, but my confidence is a bit shaken As detailed as I tried to be I still managed to mess up the organization of my parts.

Glen McCartney

Looks like you got it, I know how you feel, I thought I had everything organized when I took it apart too until that one valve fell out and sure thought I had it right when I put it back together.

SMTCapeCod

Good thread, thanks for posting! I don't learn nearly as much from the 'all went as planned' threads, or the ones that omit discussion of hiccups and problems encountered. And I can't relate to those latter types, either

1989porsche928

dont get the springs mixed up. some of thoose can't be ordered. the valve bodies received a few upgrades throughout the years.