Getrag Failure Information

[rwinslow]

After 275,000 miles of routine oil changes, the Getrag went to the transmission shop. The symptoms were:



1) Change in transmission bearing sound from cold conditions to warm.



2) Occasional grinding type of shift going into third gear.



3) Apparent clutch chatter after the transmission was warm and when starting from a stop.



4) Jumped out of second gear twice while starting up from a stop - transmission was warm.



5) Difficulty going into Reverse when the transmission was warm.



This transmission shop has overhauled countless Getrags and installed numerous NV 4500s in the First Gens. They test drove the truck twice (the rebuilder / co-owner with 40 years of experience) and felt that there were not any significant problems. Three recent oil changes did not show any problems with particle count, brass particles, etc.



Upon opening the transmission the following was found:



1) Input shaft worn by spinning bearing race.



2) All bearings worn and needing replacement.



3) All synchro rings needing replacement.



4) All gears and other shafts, OK.



The point of this message is that these transmissions, (if kept 1 quart overfilled and not significantly overloaded) are very durable but only exhibit subtle symptoms of significant problems / impending failure. The latter is probably their most significant down fall.



Cost to repair was approximatley 30% of the cost of a NV 4500 conversion.



Hope this information might help some of the rest of you.

 

[Grey Wolf]

rwinslow,



Thanks, some information is always better than none! So far mine is still running fine and I'm on the OEM clutch too

 

[BCaldwell]

getrag

rwinslow hope bad things don't come in 3's as you already know mine went also but should be back tomorrow. hope yours comes together with no major problems. Bill

 

[BushWakr - RIP]

Hey rwinslow,



I'm sorry you had problems, and I'm glad you fixed the ole girl rather than flog it and get a different truck,,,,some do you know. .

anyway, good post... nice description and rundown. .



Bob.

 

[AlK]

rwinslow,

My truck also has the getrag. Thanks for the post, good information.



BCaldwell,

Sorry to hear that your transmission went on the fritz. Just in case I need to rebuild mine some day, who is doing the repairs on your transmission.

---

Al

 

[BCaldwell]

AL the fellows at coast power train are doing the rebuild for me if you want e mail me and I will give you the whole story, I have had an adventure. Bill

 

[rwinslow]

An update. . . . . and $. 02 worth of engineering advice. . . . .



Everything went back together and back on the road again. Inspection of the failed parts showed age related bearing wear. The most significantly worn bearings were one on the cluster and the small internal bearing on the input shaft. The synchro rings were worn to the point of being almost useless. The input shaft main tapered bearing was in very good shape.



All of the gearing is in very good shape - most still exhibit original machining markings.



The rebuild shop commented that they could not believe how good of shape the gears and shafting were in.



I have typically used Mobil 1 5w-30 Oil as the lubricant but have dabbled with a couple of other choices over the past few years. After inspecting the parts, I am firmly convinced that the key to keeping this gear box alive for the long haul is:



1) Synthetic 5W-30 oil as the lubricant. A PAO base lube is preferred since PAO's have a higher shear resistance than other synthetic base stocks. Several of the bearing oil supply passages are pretty small which dictates the 5W-30 viscosity range.



2) Change the lubricant often - every year at least.



3) Overfill by one quart.



4) On initial start-up in the AM, give the transmission a chance to spin in neutral to circulate the oil.



5) Apply power evenly and smoothly. It is pretty obvious that rapid applications of Cummins torque and HP will result in lube starvation and increased wear rates.



The rebuild shop is Durabilt Transmissions in Idaho Falls, ID. Ask for Skinny. They also do an excellent job on the NV 4500's.



rww

 

[JFitzgerald]

Great info, rwinslow. Thanks. I'm at about half the miles you are, so it makes me feel better.



Just curious - How many of those miles have you had the power turned up over stock?

 

[rwinslow]

The pump has been 'tweaked' for almost 100,000 miles.