1stgenatheart

Hey guys quick question. Got a 2002 CTD with the six-speed transmission. I have herd of the sixth gear going out under highway speeds with moderate torque applied. Is there any truth to this and if so can anything that can be done to prevent this from happening? I have herd of over filling with an extra quart of fluid? Also are they running synthetic or regular transmission fluid?
Thanks

bnold

Overfilling is to help protect the front main bearing, which has been known to fail because of improper oiling especially while climbing hills.

Never heard of 6th gear issues, the 5 speed had the 5th gear nut fall of from lugging....

I'm running a synthetic

Haulin_in_Dixie

I have never heard of a six speed problem either. Contrary to what many here seem to say, the six speed is a far superior transmission to the five speed for towing. May not be a better hot rod trans, but for towing, work the crap out of it.

SIXSLUG

As I understand it the rear most bearing is not saturated with lube at the factory fill level...thus and extra quart makes for a fuller lube. I run 6 qts of redline MTL and haven't noticed any problems and get noticably better shift 'feel'.

PourinDiesel

Yeah like the others say over fill it by a quart or two.
6 speeds are monster transmissions...

1stgenatheart

Thanks a lot guys! It's always good to get more info! always open for more!

getblown5.9

Yes 6th gear will go out with torque applied which is why 6th is not to be used for towing heavy loads. I wiped every tooth on both sides of the 6th gear set rolling into the throttle when i had about 420hp. My gf was my witness to that i did not hammer on it or shift hard, just rolling into the throttle lightly to pass a car and get my exit.

My transmission guy said his buddy's shop in Pa has also had multiple 6th gear failures from cummins guys who were pulling heavy loads in 6th/OD, he even went and looked to see if there was a TSB or anything concerning weak 6th gear parts and found nothing.

duner

i've got 23,000 miles towing a 30' warrior at 75+ in 6th. give or take a few for pulling grade in lower gears. i actually talked with one of the guru's at gear vender to see if i could talk him into saying it was okay to haul that amount of weight in DOUBLE OVER, he wouldn't.

Haulin_in_Dixie

Wow, double over towing, weak sixth gear, interesting thread. I could learn a lot here!

1stgenatheart

Just wondering how do you guys overfill your transmissions?

gmctd

It's nowhere near a quart extra - the trans takes 9.5 pints - more will spill out the 'full' port - most just use the entire 5 quarts by leaving the 'full' plug in, filling thru the shift tower

Remember - that's how myth and misinformation get started - soon, some guy's gonna come on here, complaining cause he cain't get the full 5gallons into the transmission, and everyone's gonna be chippin' in, tellin' him how they did it - NOT! - it's 9.5-10 pints, or 5 quarts - 2 pints\quart

The synchros and gears were re-designed in the second version to allow better oil flow thru the needle roller bearings, due to some bearing failure in the first issue - second version also got the 1.375" input shaft - new bearing\synchro kits have the new-style synchros