T90 Countershaft Wear

Having to replace the mainshaft on my t90. This rebuild has probably 7,000 miles on it. The countershaft has some deep wear on it. The spacer sleeve looks good on the cluster. What could have caused this?

 

Was the countershaft replaced at time of rebuild? If so my guess would be inferior quality/inferior hardness

 

First question I would have to ask is where that replacement shaft came from.

 

The whole kit came from Novak

 

That's disappointing. What drove you to take it apart? 7k miles on a rebuild doesn't sound like a lot

 

My transfer case blew up and in the process chewed up the threads on the main shaft. I need to replace that shaft to use my overdrive.

 

I guess there’s a good chance that a piece of the transfer case made it into the transmission and found its way into the shaft.The transmission oil looked clean though.

 

Ill say that Novak generally has high quality parts so I'm inclined to say that something else caused the damage but, this is just my gut talking. Im also assuming the shaft in question was a Novak part which came with the kit or as an additional purchase. Not sure how a piece of debris would make it's way from the t-case into the transmission though they do share oil. That seems like wear that didn't just happen in a few minutes of run time though.

 

I’ve seen them wear like that when a needle bearing is missing.

 

Geeze I guess anything is possible...

 

Was the wear on only one of the needle brg sets and not on the rest of the shaft? Could be something like a bad needle or tiny rough spot that was on the shaft when it was made if it was on only one set of the needle brgs.
I have seen what I thought was premature wear on those shafts, why? I do not know. after all they are completely submerged in the oil down there.

 

I did replace my T-90 counter shaft and the intermediate D-18 shaft when doing an overhaul with shafts that have machine chrome on them. That was back in 1982 in my 43MB. The trans is still intact but only has been driven about 10k or less.

 

Thats not wear, thats a machined groove.
I just got done rebuilding my t90, and used a Novak master kit. It had the same shaft, with the same groove in the middle. Late to the party, but thought it might be useful info for anyone considering their kit.
JT

 

Wonder why It would need the machined groove there. Is the groove outside the area where the needles are positioned? like inside the spacer tube.
I recently bought a nos counter shaft on e-bay for my T-15 and it was smooth all the way.

 

my T90 countershaft (original as far as i can tell) is smooth all the way. it does look like that would be inside the spacer tube.

 

I wondered the same thing. That area is inside the spacer sleeve. Maybe the rough area slings oil??
Its a Novak part, maybe they could answer.
JT