I was unable to find a vss for a 42 tooth gear, so I rotated my old vss (38 tooth gear) 180 degrees and tried the 42 gear on it. It works. I also modified the hold down so that the vss could not accidentally rotate. If you are swapping up to a rear ratio 3.07, or higher, don't get rid of your old vss! I know this worked on a 1990 , but I can't speak for other year c4's.

 

The rotation of the VSS has been mentioned many times but I don't believe it's a "cut and dried" procedure. Looking at the retaining provisions of both the less than 39 and the 40 or more the only easily accomplished rotation is 180*. I don't believe that's the engineered difference of the two.

Does it allow the gears to mesh? You say yes! How long? You don't know because you don't know for a fact that it's a correct match. It would require a "cut-away" to visually inspect what is required for the correct match. 10 years ago when parts were plentiful it might not have mattered, $6 - $8 got you another gear or two. The C4 makes the drive replacement something other than a pleasant experience. A standard live rear axle car, not so much.

I believe it's worth the effort and expense to use the correct VSS. There's not many of any of the odd drive gears available and the 43+ drivens are hard to source also.

An engineer did a jig that disproved the theory a few years ago and called the person that claimed the rotation worked an "idiot"! I had that statement but lost it several "computers ago"! I've not implied you an "idiot" - I just don't "buy into" the thoughts!

I do believe it can possibly be rotated but it would require substantial effort to confirm it had been done effectively!

Good luck!

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Here's a more recent comment by someone that "understands" and visually I see similar comparing the two. There's a link back to the CF and you can see his thought regarding the fellow that "claimed" it a fit. See #6 and the link above in #5. This guy was a little more polite in his comment but it amounts to the same thought. I have to smile when I see the comment regarding the fellow that said it works!

http://www.thirdgen.org/techboard/el...-40-tooth.html

 

When I signed on to this forum in Jan., I recall some of the rules forbade personal attacks and abusive language. Are these no longer the rules? As for my post about the vss, it was a factual statement. I did order and received a new vss from Performance Automotive in LA. When I compared it to my old vss I was surprised to find that the shaft was in the same position on both vss's, so I called the company. Their "expert" claimed this was the correct vss for a 42 gear. I removed the o-ring to make it easy to put the new vss in and out if the trans. and tried it with the 42 gear installed. It would not go in to the seated depth. I tried it with the 38 gear installed and it seated. Then I tried the new vss with the 42 gear rotated 180. It seated properly, as did the old vss rotated 180 with the 42 gear. Then I went to my lathe and clamped the shaft of each vss in turn in the chuck, rotated the vss and measured the eccentricity of the housing. Surprise! They were identical. I then placed the 38 gear on the shaft of each vss, rotated it, and established the mesh point with a stationary point. They were identical. Next I did the same for the 42. I had to rotate each vss 180 degrees to obtain the proper mesh point. That is the long version of "It works."
I do not make any claims of propriety, durability, or "intelligence." If something bad happens, I will post it. It rankles me, however, that the new vss I bought can be rotated 180 degrees by simply removing the hold down, which clamps to the plastic body of the vss, and putting the prongs in TWO IDENTICAL DIVOTS ALREADY MOLDED INTO THE CASE.
Also, I found two 42 gears on ebay, but decided not to buy both.

 

I believe that I follow the procedure you used before the attempt and I would guess that if I were standing there with you watching I would have suggested "go for it". It's good if it does and it only needs to satisfy the end user. It would be interesting to be able to do the "fit" on a bench and actually be able to confirm the "contact/mating" is satisfactory. I believe that the clamp actually allows a couple degree rotation of the VSS and doesn't clamp it in just one position "flush" to the locating pads on the VSS.

This procedure might actually only be able to be accomplished with this VSS and not the later. You modified the clamp and I guess removed the projection on the plastic portion of the VSS 180* from the bolt that attaches the clamp or did you "notch" the clamp and use that as an "indexing" point?

It also seems you might have been sold an incorrect VSS also.
The one in your car was like that on the right except white? Were you sold one that was a match for the one on the left?

 

You are correct, old one on the right, new on left. Also had to get a new connector for left one. I not only cut relief for "tang" on the old hold down, but welded small projections on underside that butt against original locating pads, from which I removed the L shaped raised portions. On the bench I noted that there are a few degrees of rotation that would move the gear forward or back in relation to the driven gear, while changing very little the amount of mesh. This bothered me, but as you said, I couldn't get in the trans to see if it was important. Does the vss on left have two sets of notches for the holddown to snap into?