stumped

[wingnut757]

A few days ago my 98 C1500 started having what I can only imagine is some typre of torque converter issue. While driving at a constant speed the RPM will surge by about 500-600. This surge does not coincide with any type of acceleration, it's more like the converter is letting go and the RPM's just rise and fall back down. The fluctuations also seem to stop after about 15 minutes of normal driving. I have had no real noticible transmission issues. At first i assumed it was my tranny fluid just breaking down so to get me home I used a bottle of Lucas. The bottle seemed to do the trick for only a couple of days and now the problem is back...no better, no worse. The only difference I have noticed is that before the addition of the Lucas my fluid looked perfect and now it seems there is a bit of varnish. No smell, nothing seems burnt, just a little dirty. I haven't changed the tranny fluid for about 70k and the truck now has roughly 160K on it. My concern is that if I do change it the transmission will crap completely and I'll be on the hook for a rebuild. Anyone have some insight on this?

[trannyman52]

The converter unlocking,,,or is it falling out of OD,,,,either usually mechanically means friction material is failing,,,,not to say that it could be a problem with electrical issues...replacing fluid and filter will not change the issues unless it is related to a plugged filter,,,the good is you get to see whats in the pan !!!! lotsa glop in the pan,,,going to need some repairs,,,,clean,,,,check/clean / replace LU solenoid,,,other electrical issues......My main issue is that R&Ring the fluid and filter will not hurt trans,,,if it's shot,,,it's shot...most do not service the trans,,and are shocked to find it taking a dump!!!! The warning signs of failure are not real noticable,,,untill it is usually too late...friction materials are very durable,,but over time from shift cycles,,running low on fluid,,,heavy gas pedal,,,do wear out......gbaum

[j cAT]

given the mileage and the care you gave the transmission ,it is no surprise its worn.

I would drop pan and see whats up. sounds like its dropping out of 4th gear. could be electrical/worn valves. if the valves are worn then other parts are worn.

being of this age most likely it has dexron III in it. dexron III turns to acid after 20-30,ooomi. this is how these are worn or should I say eaten by the acidic fluid.

If you get this rebuilt make sure they use dexronVI. I say this because dexron III is much cheaper. GM does not even license this fluid as it is defective. [gm 2006]

[wingnut757]

I am gonna go ahead and R/R the fluid and filter this weekend along with the LU solendoid. I failed to make the connection earlier but it seems like a great idea. I was in bumper t bumper traffic about a week before this all started and the truck died on me twice. I chalked it up to bad gas as i had just refueled and a bottle of dry gas seemed to remedy the problem. Thanks for the input guys.....and here's hoping that I'm not gonna need a rebuild.

[Schurkey]

Originally Posted by j cAT

being of this age most likely it has dexron III in it. dexron III turns to acid after 20-30,ooomi. this is how these are worn or should I say eaten by the acidic fluid.

If you get this rebuilt make sure they use dexronVI. I say this because dexron III is much cheaper. GM does not even license this fluid as it is defective. [gm 2006]

I'd say that's an exaggeration, and alarmist.

[j cAT]

Originally Posted by Schurkey

I'd say that's an exaggeration, and alarmist.

you can say whatever you want.

I'm just speading the word about GM reporting that in 2006 this all came about.

since I was lucky to work with a aircraft engineer that told be back in 1998 to drop dexron III for the same reason GM in 2006 dumped dexron III.

if you look you will find this document . its here on these forums.

[wingnut757]

Looks like i got it. I ran a can of the Seafoam transtune through it for about 100 miles, changed fluid/filter and all seem to be working great. And as a bonus no metal in the pan!!!!! thanks guys