T-90 Reverse Idler Gear

I rebuild my T-90 this days. It have a Reverse Idler Gear with 15 teeth.
Looking at other T-90s i have at home, i noticed some have 16 teeth and others 15.
Does anyone know about that? is it realy metters?

Ziv

 

There were 2 models of the t90 an A model and a C model. The difference was 1st gear was lower in the C model. The "A" model had a 2.79 1st gear and the "C" model had a 3.34 1st gear. 1st gear is tied into the reverse idler when reverse is used, this would be why they have different tooth counts on the idle gear as you noticed.

 

Thanks Mcruff.
I know the cluster gear came with 33 or 35 teeth, which gave the ratios you mentioned. Is there a rule that reverse idler with 15 or 16 teeth will fit only certain cluster gear?
Ziv

 

Yes. The reverse idler must match the cluster gear and the first speed gear or they won't mesh corrrectly.

 

I asked Eric at Novak. He answered :"There were 15t and 16t versions, the former being produced from 1965-1971. They interchange with each other".


Ziv

 

during my rebuild i had the same problem, i had a chewed up 16t and the replacement was a 15t. i also had bought a new 1st/ rev gear, but i put it all together and they seemed to mesh fine. haven't done a road test yet though

 

Interesting. The idler doesn't affect the gear ratio, so the number of teeth would not matter as long as they mesh properly and are the right diameter.

 

Thats the problem, the tooth count is different which will directly effect the diameter. If the diameters are the same and the tooth count is different they will have different diametral pitches and won't work.

 

No solution yet!
I have to rebuilt my case and finish it. All wait for the 15 / 16 teeth idler answer.
Any other ideas ?

Ziv

 

I understand what Mike (Mcruff) is saying, but Eric has lots of experience with these, so I'd tend to believe him. I'd say put it together and see how the gears mesh on the bench. You should be able to tell whether it's going to work or not at that point.

 

Maybe I can shed some light on this. I recently rebuilt a T-90 and had both sets of gears side by side. The 15 tooth idler gear that I had was definitely a smaller diameter than the 16 tooth idler gear and there is no way it could have meshed correctly with the 1st speed gear and the cluster gear. Eric is very knowledgeable. I'm surprised he said that.....Not saying he is wrong, but that's what I found on the trans I rebuilt and I've run into it several times before. If you want to be safe, I'd get the correct gear. Nickmil.

 

Thanks all.

Im surprised that this question was never came-up here and feel cofused from the inputs.
Any way, i will keep the original set-up: use the old idler (it looks o.k) and install a new countershaft gear with the same teeth (33). All other parts are new !
Hope it will be good. This rebuilt T-90 will seat on the shelf ready to install just in case ...

Ziv