Engine/Transmission (1994 - 1998) Fifth gear diagnosis

[DEddie]

Decided to change the clutch on my 95 2500 still working fine but has over 320 k on the original, it can't last forever. While I have it apart I feel I should replace the fifth gear . I understand this is a weak spot. Question is,... can I tell if the fifth gear nut is starting to back off. If it looks good I may just take my chances and leave it be.

If I decide to change it, what is the prefered fix, stock or I understand there are some aftermarket upgrades which include the gear and output shaft.

Any one had any experience with this??

 

[JGK]

My feeling is, if its still in place and tight after 320K miles, leave well enough alone and ignore it!



On the other hand, you may want to have the transmission "refreshed" (new syncros and bearings). In that case, they'll need to remove the nut and gear to tear down the transmission. There are a couple of fixes. One of the cheapest is a new nut with set screws to "stake" it to the shaft. The best fix seems to be a fully splined shaft and new nut from one of several sources (Standard Transmission, Blumenthals, or Quad 4X4). Those will cost considerably more.



But at 320K miles, it doesn't sound like you're driving it in such away as to contribute to it backing off, which is usually due to pulling a load in 5th with the engine lugging a bit all the time. So unless you plan to do that, the cheap fix may be adequate.



-Jay

 

[Bob V]

Here is my 5th gear nut story. At 50,000 miles on my '97 I wanted to check the nut before I went on a 2,000 mi trip towing our travel trailer. I got the Dodge upgrade nut before I started. Left the trans in the truck, just pulled the transfer case and tail housing of the transmission. When I got it all apart it looked fine, the nut hadn't back off, the staking on the nut still in the keyway of the shaft. I thought, what a waste of time. When I checked the tightness of the nut there was only about 10ft lbs of torque on it. Took the nut off, looked like the threads had been "pulled". I personally don't think that the nuts simply back off, the threads are stripped and the nuts pushed off. If the nuts simply back off, the threads would not be wasted. I thought , at least I caught it in time before the gear got loose on the shaft, wrong, the gear slide right off and had been hammering on the none splined of the shaft. Since I didn't have a new gear I used Locketite 680 to secure the gear to the shaft and 277 to secure the new nut. That has been 150,000 miles ago with no problems, even with 300+ hp and towing 7,000 + lbs in 5th gear. I'm hope that posting this will not jinx me, probably 5th will go out tomorrow, but I am glad I checked it and did what I did.

The job is not bad, 4-6 hours of work, but I would let the Locktite cure overnight before refilling and driving. Also have a GOOD quality 10mm 12 point wrench and socket before you start, some of those bolts are TIGHT.

Bob V