Engine/Transmission (1998.5 - 2002) 5th & 6th gear gone

[jstyer]

My buddy, who has a 2002 3500 2WD HO, was traveling down interstate 79 the other day when then the truck started bucking (like when a an auto lock-up goes nuts) and then had no 5th or 6th gear. So far the dealership hasn't been able to tell him what's wrong but want $2600. 00 to rebuild. Anyone had this problem before and if so - what happened?

Thanks

John Styer

 

[John Berger]

synchronizers maybe. You didn't say whether he could shift through the other four gears, so I'll assume that he can. I don't know what a good price on a rebuild is. Did they tear the transmission apart or was that just the answer he received when he told them the problem? I'm assuming the truck is out of warranty.

 

[jstyer]

Update

You are correct in that he still has all 4 forward gears and reverse and they did not tear transmission apart to diagnose. I told him originally that I thought it was synchronisers and that it wasn't like the five speed with the notorius "nut problem". The truck is under 100k miles but well over 36k miles and believe that the transmission falls in the 36K bracket.

John

 

[Gary - K7GLD]

The syncronizers ONLY assist shifting, they don't provide any actual drive path for power - if the transmission actually GOES into 5th and 6th gear - but won't move, that's ONE thing - if it can't be SHIFTED into 5th or 6th at all, that's something else perhaps...



We need clarification as to what is meant by "no 5th or 6th gear"...

 

[RustyJC]

Just a little clarification. On a fully synchronized transmission the gear pairs are in constant mesh and free-wheel on the mainshaft - the gears on the countershaft are another matter. When the gear is engaged, the synchro teeth on the gear engage slots in the synchro drum (splined to the shaft through the synchro hub), so the synchro assembly actually locks the selected gear to the mainshaft through the teeth and slots. When one shifts gears, he is actually moving the synchro drum back and forth over the synchro hub with the appropriate fork.



In the case at hand, I'd suspect the 5/6 fork or (more likely) the 5/6 synchro drum/hub assembly is tango uniform, unless it's a linkage problem. Can he get reverse (i. e. , pass through the 5/6 gate)?



Rusty

 

[Gary - K7GLD]

Ditto what Rusty sez - and my point... The "bucking" bit might be a clue...

 

[jstyer]

further update

Yes, it will go into 5th & 6th but won't engage. He also has reverse. He lives in the Hagerstown, MD area and would also like to know where the most reputable and hopefully experienced repair facilty might be located. He is a member of the TDR, but is not online to date.

John

 

[RustyJC]

The 5/6 synchro drum splines to the hub or the 5/6 hub splines to the mainshaft are probably sheared if neither 5th nor 6th work. The hub can't transmit torque from either gear to the mainshaft. It could be shattered and lying in the bottom of the transmission, as well.



Personally, if the fix were on my nickel, I'd call Standard Transmission or Blumenthal's to price an exchange unit before shelling out $2600 to a dealer.



Rusty

 

[jstyer]

Thanks

Rusty : Thanks for the info. I will forward to him.

John

 

[Gary - K7GLD]

Wonder what would cause this sort of failure, other than defective parts - seems pretty rare, first I have heard of in these trannies - wonder if maybe the dogs/gears were not fully engaging due to improper adjustment/setup?

 

[RustyJC]

Gary,



I'm an old man, and my memory's about gone, but I can only recall this NV5600 problem with one other truck over the years. I'm certainly willing to be proved wrong on that, though.



Rusty

 

[jstyer]

?

I haven't come across this occurence before either, which is why I posted. I have 70K on my transmission and haven't experienced anything like this before. I figured this was something very rare. Once again, Thanks.

John

 

[Gary - K7GLD]

IF it was in the lower gears, you might assume rough treatment like speedshifting, but not in the upper gears, and lube problems would likely have affected other internal components LONG before this sort of failure...



I've heard of cases with older 1st generation trucks used in constant heavy towing situations, where the "jackhammer-like" firing impulses of the Cummins would eventually literally peel teeth off the transmission gears - maybe this is somewhat similar in rare occasions...

 

[jstyer]

Towing

He tows a trailer with at least four horses all the time. He is a steer wrestler and rodeos all over. Maybe you have hit on something.

John