GPS (Getrag preserva..) long sorry:(

[BJMarshall]

I am soon going to put a clutch in the truck and I guess I better look at the Getrag while I am in there. I am hoping to get a little help figuring out what to look for before I get it out. I have the manual for it so I can't imagine it being that much trouble. I have researched putting in a NV4500, but that will cost approximately what I paid for the truck. My truck is not overly powerful, and I don't abuse it, so I feel like I should be able to get another 100k out of the transmission.

Right now, it works OK. It shifts good with no grinding and little effort. I have been running it with mobil1 5w30 overfilled, and so did the previous owner. Last weekend when I changed the oil, I switched to 15w50 to see if that would help. It still shifts good. It's a little stiff when it's cold, but after about 5 miles, it's fine. It is a good bit quieter. The only problem I have is a terrible noise in 4th gear. Anything below 40mph in 4th and it vibrates the crap out of the truck under acceleration and it's very loud. It starts getting quieter about 40 and is completely gone by 50. It just doesn't feel right to wind 3rd out that far, but if I do, the noise is non existant. I have been revving it in 3rd to keep it from doing this, because I'm sure it is not good for it.

Any suggestions on what to look for when I get it apart? Also, any input on where to get parts would be appreciated.

 

[SRadke]

Standard transmission is a good source for parts. my best suggestion is to take the top off while you have it out and look for things like endplay in shafts or wear on gears. They'll be subtle but could be there.



-Scott

 

[1stgen4evr]

noise in the getrag?

My bet is that you do not have a problem in the Getrag. You MUST reve the engine in third to get past what you are hearing. The noise is the result of the dramatic torque pusing that the cummins is capable of as each cylinder fires at low rpm under exceleration.



Specificly, the noise is in the spring center of the clutch. It is a know condition that has existed since the introduction of the cummins into these trucks. There were manufacturers alerts on this long ago. If you impose that condition on the clutch enough, you will indeed be changing it. You indicate that you may be doing so soon anyway. Why are you think of a clutch change? Is it sliping? If it isn't, you won't likely get much better result from any other type of clutch. The original Sachs clutch is quite good for stock output.



If you will look back at my post on the getrag, you will find some input on checking the condition of it. Briefly, drain the oil and look in one or both of the side covers and inspect the gears for any scuffing. They should be mirror bright and from what you indicate I think they will be.



With a soft bar, pry the counter shaft forward and aft. There should be NO movement as the bearings are set up to have preload. If you have lots of miles, you may very well need to reshim for the proper preload.



Generally speaking, you will expect to see trouble with the front countershaft bearing as a first cause of failure. Close to that will be the pocket bearing between the main shaft and input shaft. Both of these will be total driveability failure. Less often but certainly a problem is the happening of low oil and the resultant scuffing of one or more of the gear sets. You could see problems with input to countershaft, third on the main shaft and counter shaft, or OD on the main shaft and countershaft. Use a flash light and look closely.



Rarely but sometimes a failure of the speed bearings under the gears on the mainshaft will be seen. If you have not experienced high heat and "blowing the oil out" you don't likely have scuffed gears.



You don't indicate that you are "overfilling" the transmission. This is a must. Look at the posts on this. The stiffer shifting is the result of the higher viscosity lube but you will see better life on the transmission if you continue the heavier oil.



At about 350k miles I began to have difficulty/failure of the syncro on the third gear shift. Because I could and did find a method to shift (carefully) without the syncro, I ran on to 410k miles. Had it out, changed the syncro, and reshimmed the bearings. It is rolling up miles still. I have spent a modest amount of money in the 420 miles that the truck has been run on the original Getrag.



Plenty of folks have had failure, but what you have said doesn't lead me to think you are near that.



Standard Transmissions as well as Man-Tran in Tallahassee are both very reliable sources of parts.



1stgen4evr

James

 

[BJMarshall]

Thanks for all the info

Thanks for all the info. I am overfilling. That's in there. I fill it up to the top bolt hole in the PTO cover. I am going to replace the clutch because of some serious chatter on takeoff. I suppose the chatter could be from the springs as well. I was thinking damaged flywheel or pressure plate, but now that I think about it, it really doesn't feel the same as on other vehicles that have had overheated flywheels. I know the previous owner put a cheap reman clutch in it about 20k ago. If it is the clutch causing the noise and vibration, why only 4th gear? Does it have something with 4th being direct?
No signs of leakage or overheating of the oil. The oil has been very clean each time I have changed it. Everything I could see with the mirror and flashlight through the PTO cover looked good, but I couldn't see everything. I didn't check for anything being loose, but I will check that when I have it out.

 

[1stgen4evr]

why only 4th gear?

Well all the other gears will allow the truck to accelerate rather than hold it back to the point that you get the growl. They will however do it in third if you are loaded and are at the low rpms.



1stgen4evr

James

 

[JKurley]

OK 1st gen, I,ll bite- Whats your unique way of shifting wo a syncro?

 

[dpuckett]

In 4th gear with 3. 54s, you are lugging the ever living dog crap out of the transmission at less than 40. Ok, maybe not, but you're definitely on the borderline. 35 is the slowest I drive mine in 4th. If it sounds like the engine is going to lift off, try advancing your timing, and adjusting the valves, then run some injector cleaner through the tank. I can run mine up to about 45 in 3rd; last set of 3. 54s I had I could run 50 in 3rd (and 80 in 4th, 98 in 5th Oo. )



And yes, James, when I take a 15mph corner in 3rd, it does growl taking off.



Guys, these arent the diesels of old- REV IT UP A LITTLE BIT!!! It wont hurt a gol-durn thing.



Daniel

 

[1stgen4evr]

OK 1st gen, I,ll bite- Whats your unique way of shifting wo a syncro?

Note that I said carefully, but in addition, it helps to have driven a 58 model Mack about half a million miles which had no syncros in the first place. But the gist of it is that if you will match the engine speed to the correct rolling speed for the next gear (in this case third), the transmission will shift without the syncro. The engine speed has to be held higher (not wide open) than if you depend on the syncro to make the match.



That said, I knew full well that it was time to change the syncro all along. I was on the road and doing other things to the point that I neglected it for too long. After I changed it, I thought dang, I shuld have done that lots sooner.



1stgen4evr

James

 

[BJMarshall]

OK after 1500 miles driving a friends PSD 6spd dually, I think maybe my Getrag doesn't make all that much noise. Actually, after having to rev the PSD so much I got used to it. When I got back in my truck, I was revving it a little higher than normal and it worked great. It also seems to be doing real good with the 15w50 oil in it. I think I will stick with that at least until the weather cools off some.