jared87

So i just purchased a 91 ctd off of my best friend and he just had the tranny replaced about 8 monhts before i bought it... he did the nv4500 conversion from a getrag.... i helped him put the tranny in and it was a rebuilt one out of a 95 i believe.... the other day i was just towing a rockcrawler on the trailer about 55 mph and the truck all of a sudden just popped out of gear...so i put it back into gear and nothing...just straight up neutral...doesnt make nay noise or anything just no go.... can someone tell me if this is a common problem and or whats the way to fix it... i hope i dont need a new tranny....

Micaiahfied

the only thing i've heard they are common for is 5th gear going bad. welcome to the site, i'm sure someone will have a better answer in a little bit.

BearKiller

Different transmission, but, we had a ZF5, in a Ford diesel, do the exact same thing, pulling a big gooseneck load of cattle.

Just cruising up I-71 and it sort of fell into neutral, no big crunch, no jerking, no unusual noise before, no warning, tried every gear and all were like neutral.

We coasted her to the shoulder and it acted just like the driveshaft had been removed, shift through the gears like a new transmission, but it wouldn't wiggle.

The only fix was a new transmission.

I know this doesn't help your question; but, I didn't want you to think you were being singled out.

csramsey640

If you were in 5th gear, 9 chances out of 10 its the Nut that hold %th gear on. The come off, and you have no 5th gear. The Mopar fix was a nut with a set screw or something similar, but the true fix would be a fully splined main shaft. They say dont lug a NV4500 in 5th.

If you were in another gear, you may have more problems.

redhauler

This is the Best way to fix the 5th gear problem'Replace mainshaft with this all spline and keep on haulin.

rich

first on the 4500 dont tow in it under 65 in 5th gear it lugs it not good, second you might have busted the main input shaft. i've done that about 4 times but it usaully makes a horrible grinding noise

flashgordon

ok could some one explain the full spline deal to me?
I have replaced many fith gear and nuts, on NV4500 and have hered of the full spline idea but that pitcher don't look any diff then the ones i have put the gear and nut pkg on?

redhauler

Here is a better comparison the top is factory and the bottom is replacement .

redhauler

Overloading Aggravates Problem

Before discussing the problems associated with factory partial spline and aftermarket full spline mainshaft designs, I want to point out that they are good quality parts made by reputable manufacturers. The 5th gear failings they have are not metallurgy or workmanship related. Shaft wear and gear failure is primarily due to design, but diesel engine harmonics, and overloading also are significant factors. Owners of diesel powered NV4500 equipped trucks often greatly exceed the recommended horsepower and load ratings for their vehicle. We have seen these trucks with engines putting out over 500 horsepower and 1,000 ft-lbs. of torque. We have also seen combined truck and trailer weights exceeding 40,000 lbs.. Now, when you consider the NV4500 is rated for up to 460 ft-lbs. of torque and 19,000 lbs. combined truck and trailer weight, you can see why part of the responsibility for transmission problems must rest on the shoulders of truck owners who grossly exceed the vehicle design limits and insist on making their ¾ or 1 ton work like a 2 or 3 ton truck
Mainshaft Types and Weak Points
Now I would never do that Ha Ha
To support the 5th gear, the factory mainshaft has both a splined area to transmit torque and a smooth machined surface for the fully internal splined gear to press onto. The end of the mainshaft is drilled and tapped for a pull rod so the gear may be pressed on the shaft without damaging other components inside the transmission. With this type of shaft, only the tips of the gear splines are in contact with machined support surface of the shaft. This area is also directly under the gear teeth. Over time, the gear splines will actually wear into the shaft. As this wear continues, the fit between the gear and shaft becomes progressively looser. At this point, every time you accelerate or decelerate in fifth gear, the gear moves back and forth between drive and coast. This back and forth motion against the nut is what eventfully causes the nut to back off. Since the mainshaft bearing is inboard of the gear, the transmission will usually operate in all other speeds.
Click Here for more details on the problems and fixes.(Great site)

jughead

redhauler i am glad to see that at least one person out there agrees with me. i have said for years that most of the drive train problems with these trucks is due to overloading. havent done any standard trans work in years but almost all the problems i have seen with autos has been abuse or my stupidity. you made my day.

BearKiller

I never see it mentioned, but back when they were new trucks, the fifth-gear was prone to failure in the Getrag, also.

We drove one back to Kentucky, from far south Mississippi, when it was about a month old, with fifth gear out.

We stopped at a large Dodge truck dealer, in Senatobia, Mississippi, to see about getting it fixed.

At that time, the Getrag was considered as a non-servicable unit, to be replaced in it's entirety.

The service manager got on some kind of parts hot-line and could not find a single transmission in the entire United States.

He took us out back and showed us around a dozen new Dodge/Cummins trucks that all had lost fifth gear, and were waiting on replacement transmissions.

When we got back to Kentucky, it was over six weeks, before the local dealer could get hands on a Getrag to fix our truck.

Talk about customer support.

I often wonder what went with all of those "disposable" Getrags; were they tossed in the dumpster??

PapeCAT

https://www.dieseltruckresource.com/...6&page=5&pp=15

the "unservicable units" were sent back to get remanufactured but still were being setup too tight, not per chryslers guidelines of .006 preload. which led to even more failures and more warranties, after being put back into service in new trucks... GO figure why everyone hates the getrag. When set up properly it is a very stout unit.