The trans isn't running hot and the fluid isn't changing color, but it seems that the 2-3 shift is happening later than usual like the truck feels like it is on a hill. It seems to go through all 4 gears when I accelerate and there is enough room to do that (hard to do in this town with alot of traffic and 30mph roads), but it seems that 2-3 is happening later than usual and at a higher RPM. I just replaced the TPS a couple months ago and a few months before that. Replacing it each time made the shifting better.

EDIT: I heard that a dirty air filter can cause bad shifting since it causes the computer to go nuts. I have a Spectre 3.5" tube cone filter on this and the last time I put a new one in was December 2010 (could not clean the old one since it was rotted). Could that be the cause?

I checked the fluid level and condition again and it seemed fine.

Considering the recent temperature drop, could this be in response to that? Could my cooler be overcooling the fluid and the computer is responding to that? I touch the cooler now and it is cooler than before (but then again, the temperatures are just above freezing). I found this: http://www.hotrodders.com/forum/4l60...de-148841.html
May be true on a full size 02, but what about a 98 S-series?

At this point, I am a bit concerned. 4L60E charts don't give a clear explanation. Otherwise, this trans works fine. The 1-2 shift is variable when it comes to how firm it shifts, so it isn't always the same as 2-3. 3-4 and lockup are always undetectable except if I look at the tach. This is all with minimum throttle (just barely touching the gas). I don't rev it up. Rarely past 3,000 and almost never to 4000.

 

I just had to have my trans rebuilt for the second time when the seal on the output shaft of the trans blew and leaked all of the trans fluid into the transfer case. No sign of a leak, just a slow draining of fluid and black crap in my fluid from the roasted 2nd-3rd clutches. Low trans fluid levels will burn up 2-3 first.

 

Oh wow. Twice rebuilt? Wow.

Last time I checked the transfer case fluid a few weeks ago it was fine, so I don't think that is happening here, but now that you mentioned it, I disconnected the vac lines to the t-case at the check valve near the firewall and when I uncap them after driving it I hear a slight hiss. Weird. I will check the T-Case fluid more often now that you mentioned it. Thanks

The good thing about this truck is that that can't happen as easily (but can still happen) on this trans since I have a deep pan (2 more quarts of fluid + deep pan filter + .5 qts more with the cooler) and I check the fluid often and it doesn't seem to leak at all. Plus I have Lucas Trans Fix in there and it seems to smooth shifting when the truck is cold, especially with this cooler (Last winter I drove this truck in -20F temperatures and it drove normally).

2-3 goes first if the fluid is low? Was the black crap in the fluid the same as what was in the photos I posted or did you have alot more? For some reason, it is shifting normally now (actually smoother and 2-3 is happening at a lower RPM), but I don't know if that has to do with warmer temperatures today (50F). There is barely any black stuff on the dipstick now. Maybe it is the colder temperatures having an effect on it with the cooler and I should consider bypassing it? I touched it after accelerating it to 60mph from 30mph Test Track-style (As in Test Track at Epcot at Disney World) and then went from 60-0 in 200ft (hot brakes stop better for some reason), made a turn and stopped and felt the cooler and it was just warm. As in, those winter hand warmers you would use for camping are hotter than my trans cooler. Probably not even 100F and this is touching the bottom of the cooler where the fluid flows across. A couple days ago I used the IR thermometer on the bottom 1" of the cooler and it was only 85F. Maybe I should buy a travel trailer and then the trans will be at the right temp because I had too big of a cooler installed that takes up 1/3 of the area of the radiator?

Thanks for the tip.

 

I drove it 140 miles roundtrip tonight and it was doing the same thing. 1-2 was below 2,000 rpm, but it seemed to want to hold in 2nd for a long time before going into 3rd. Around 2,500 rpm. I checked the fluid before and halfway and there was only a little bit of black stuff in the fluid. Do these computers keep the trans in a gear longer when the trans is cold? Every time I pull over, the temp at the cooler line and the trans cooler is barely 100F. This is even when driving on windy/hilly roads where the shifting was frequent. Could I have another TPS going bad or a computer problem?