hippyjr

I have a 1998 chevy silverado 4x4 2500 with a 6.5l. with 366,000km on it.
I'm having problems with the tranny shuttering when it shifts from the 4th to 5th into overdrive. And when I accelerate slightly, only when it's in overdrive.
If I keep accelerate slightly and hold it there while it's shuttering ex: when I 'm going up hill. It will kick down to 3rd gear and wont come out untill I shut the engine off for a couple of minutes restart and it returns to normal.
I have changed the filter and fluid, fluid was verry dark, light smell ( tranny must of gotten hot ) no metal in pan a little bit of gray gunk on pan. I'm told that this is normal? I've tried to touch the brake pedal when it's in overdrive and when it's doing the shuttering and nothing happens just stay's in that state.


Thanks in advance

Gilbert@Ace Racing

Well Hippy... hate to tell you this but it is not shifting into 5th gear. The 4L80E is a 4speed overdrive with Lock-Up.

What you are feeling that makes you think it is going into 5th gear is the Torque Converter Locking Up. And because you are feeling a shudder in "5th" or Lock Up that tells me that the Torque Converter Lock Up Clutch is slipping.

This is a very common occurance in higher mileage vehicles... it simply has worn out.

I would be happy to discus this in detail with you should you call me.

817-605-3151 is my number here at the shop.

g

fenix999

iTrader: (17)

anybody with some more info, i mean i know these trannies are "4" speeds but never really understood how lockup works or how it affects the tranny etc. It kinda does feel like another gear in a way but not really. Anybody have a link or soemthing that physically shows me what function overdrive and lockup have in relation to a 4L60 or 4L80??????????? Gotta learn more about this stuff i have the concept and terms but totally lost on actual function of things

hippyjr

Thanks i'll call you on monday

hippyjr

I put a new torque converter in two weeks ago problem solved.
I've towed well over 5000lbs on a 7 hour trip up north with lots of hills.
Overdrive held perfectly.

Thanks for the advice ratchthed.

DeltaT

iTrader: (5)

Without the lockup, the converter is a fluid coupler that always has some amount of 'slippage' - the input side of the converter (attached directly to the motor via the flexplate and converter bolts) always spins slightly faster than the output (or 'floating') side.

With the lockup, there's a clutch-type disc on the normally 'floating' part of the converter that, when fluid pressure is applied to it, gets forced forward and 'locks up' against the engine-attached section of the converter, eliminating any slip. That's why engine rpm drops 200-400 rpm and it feels like one more gear. Since slip is eliminated the tranny generates less heat, and with efficiency up, you get a bitmore mileage.

Jim