In the process of replacing the hanger bearing on my '91, I found that there was no nut holding the yoke on the output shaft. The threads on the shaft don't seem to be damaged, and it can't have been missing very long because the threads and the nicks where the nut hit the yoke are still clean.
My question is what damage, if any, did it likely do to the transmission to run with the yoke loose?
I won't be able to try to buy a nut until Monday, but in case my Dodge dealer can't supply it, what are the specs if I have to go to a fastener house? It looks like 20mm diameter x 1.5 mm pitch, assuming it's metric, but I'd like to be sure. Also, should it be a self-locking nut?
Btw, I bought the truck new, so I know the transmission has never been worked on.

 

As long as the yoke is not wobbly on the shaft it will be fine.

It should be nylock, and a punch or cold chisel nick to stake it on would not be a bad idea.

 

From personal experience, I wouldn't drive it until you get a nut. The output nut came off on mine while on a trip and it took me a couple hundred miles to catch it (found it when I checked on the oil leak under my transmission) but the transmission growled constantly after that and eventually died a few thousand miles later. Like Wanna said, if it's not wobbling and not leaking, you hopefully are fine as long as you get a nut on it before you do damage it.

I can't help you with the thread spec but I can tell you that the factory nut does have a large washer built into it and the manual says that the torque spec is 280 ft. lbs.

 

I have seen, and had, a few to back off, but the nut has always remained trapped inside the yoke.

On the Getrags, I am pretty certain that nut is a steel locking nut, the kind that has the last couple of threads sort of smashed.


If memory serves me, it takes a 2-5/16 socket; BUT, don't go out and buy a socket that size on my recommendation.


This outfit should be able to help you with the nut :

http://www.blumenthalautomatics.com/



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I found a couple of other threads about the nut coming off (ok, I should have searched before I asked).
I was about 150 miles from home when I started to hear a loud rattle every time I decellerated, at any speed. Since the hanger bearing was toast anyway, I limped home, listening for it to get worse. It didn't. When I got home, I found the nut missing. It was definitely gone, not trapped inside the yoke.
There is no play between yoke and shaft or between shaft and case, and the oil level is not down. I assume that whenever the nut came off, it fell out pretty quickly. If it had been bouncing around for any length of time, the threads would show some damage, and they don't.
The part about the loose nut causing speedometer fluctuations is interesting. I've had that symptom for a year or more, but until now everything I've read indicated that it was an electrical problem. Now I'm worried about how long I may have been running with the nut missing or at least loose.

 

I guessed right about the nut. If anyone else needs to find one, it is a 20 mm x 1.5 mm. As I suspected, my Dodge dealer didn't have it. According to his computor, no dealer had one, even though the manual says it should be replaced when replacing the seal. He might be able to order one, it might come in 2 weeks and would cost $15. Fastenall had them in stock, $1.75. Theirs didn't have a captive washer, so I had to use a separate one. It wasn't self-locking, so I used loc-tite. The shaft is hardened, so staking it wasn't an option. I'll have to keep watching it to make sure it worked.

 

Is that 20mm x 1.5 threads-per-whatever ??

At that price, I may lay in a supply for just-in-case.

Thanks for sharing your findings.

 

It's 20mm diameter. With metric threads, the pitch (1.5 in this case) is the distance in millimeters from one thread to the next. Btw, the socket size is 30mm.