Thrust shim problem/question

[M-P]

Got the transmission apart yesterday to do the snap ring fix and noticed some odd things.

A) My transmission housing had two mainshaft thrust shims installed in it...one was 1.067mm thick and the other was 0.620mm thick...making a total shim thickness of 1.687mm. But the manual states "Do not use more than one shim."

and B) I measured for the new thrust shim and got measurements of (A)=2.31mm and (B)=0.02mm, so using the formula in the shop manual that would mean I need a shim thickness between 1.27mm-1.34mm. But the maximum shim thickness available seems to be 1.15mm.

What I found to be my required shim thickness seems to align with why my transmission had to shims in it to begin with, but I don't like doing work that doesn't follow the service manuals guide lines.

Should I use two shims to get it between 1.27mm and 1.34mm or just use the max shim size of 1.15mm and have that little bit of extra play?

Also, I must note, that I didn't take apart the main shaft with the except of the outer bearing to get the measurements. Any help would be appreciated because I need to order my shim today, so that I can have it for next weekend.

 

[nigel]

This is a good question for "Super Larry".
I'd be wondering the same thing.
If the "mantenance manual" says "not to exceed one shim" there's a reason, but only more important reason is to have the "correct" shiming

Cheers
nigel

 

[drew]

You are replacing the housing too...correct?

Drew

 

[M-P]

Yes I am replacing the outer housing, snap ring, outer differential bearing, differential oil seal, and shift linkage oil seal.

 

[drew]

This question is best directed at Basch Accurate Service (PHX), Science of Speed (PHX) or Dali Racing (San Diego). They all would have lots of experience rebuilding the NSX transmission.

I would suspect that you would add in an extra shim, rather than extra play. But my transmission is still on the floor awaiting disassembly, so my opinion means little.

Can determine if you took apart a virgin Factory assembled transmission?

It would be interesting if the Factory put in the extra shim OR if your car had a faux snap ring repair (where they replaced the snap ring and nothing else).

Also, make sure you clean out the oil strainer, it will be chock full of debris and chips.

Drew

 

[drew]

update:

Use two shims.

My trans had two shims from the factory. When I replaced the casing, I was also forced to use two shims (one different).


In fact, I spoke to a rebuilder who stated that he has never seen only a single shim, ALL OF THE NSX TRANSMISSIONS he has broken open had two shims inside.

Drew

 

[Larry Bastanza]

If the "mantenance manual" says "not to exceed one shim" there's a reason, but only more important reason is to have the "correct" shiming

Cheers
nigel

Yes the reason is that the manual is wrong. Every one I have ever rebuilt had two shims, and still does.

Regards,
LarryB