2001 4l60e 4x4 issues, sometimes...

[blackhemi4x4]

Im going to try to explain this issue as best as I can. I've searched high and low, and NONE of the common problems for this transmission seem to help on what is going on here.

 

This issue only seems to happen while moving the throttle position. It does not happen on steady throttle positions. So, normal acceleration, everything seems fine.

 

I call the issue a confused 4l60e. If I accelerate, lets use 50% throttle, and near the shift point, if i then start to release the throttle, the transmission will kind of hang, as if its not sure if it should stay in first or go to second. It will "hang" for as long as i keep moving the throttle, but will pick its gear once I stabilize it. Usually, its a smooth shift but sometimes, its harsh.

 

This also happens sometimes when slowing down and then accelerating again before a full stop. A bit more common on right turns, since you have to slow pretty slow.

 

Now, the hard shift in these situations are different then any other hard shift I've had in in any other car/truck. It doesn't do it under heavy throttle, but can during moderate. 75% or less throttle. The best way I can describe how it feels is like a slide hammer hitting it. I guess like a shift kit on steroids feeling. Its chirped the tires on slow turns when I give light throttle coming out of it, maybe 25% throttle. Its almost like the the transmission is trying to catch up to the engine speed. Not sure if its a torque converter or trans issue.

 

I have not had any CEL's, On hot days, 90+ degrees, the trans temp is right around 180-185 degrees in traffic. I havent changed the filter or fluid yet, but I think it does need it. Not burnt smelling, but not fresh smelling and looking.

 

Where do I start on troubleshooting this. Anyone ever seen anything like this? And its only sometimes, but never when its just normal steady throttle positions.

 

It turns 2000 rpms at around 70 mph, not sure what rear end, but may be 4:10?

 

Please help.

[Doug_Scott]

The issue of slowing to go around a corner and the engine feels like it is catching up to the trans(I know you said it the other way around, but I think this is what you meant) is most likely due to the transmission automatically downshifting to first gear while the truck is still moving. When the transmission is in first gear, and the shift lever is in drive, there is no engine braking. The trans will free wheel, and if you do not have your foot on the gas, then engine will return to idle. As soon as you touch the gas, the engine will flare up to match speed with the transmission.

If you put the shifter into low gear, this will not happen. I am not sure what gets applied in the GM transmission, all my trans experience is in the Chrysler 904 and 727. In those transmissions, the low/reverse band is applied to give engine braking in manual low, otherwise the over-running clutch at the rear of the case will free wheel and not provide engine braking in low gear.

 

In other words, the free wheeling is normal behavior.

 

I have 4.10 gears, engine rpm at 60mph is around 2k. 70mph is more like 2500 rpm.

[blackhemi4x4]

Cool, I must have the 3.73's then.

 

The only difference in the free wheel that you described is when the get to that "matching" point, its harsh. Wheel chirping harsh at low engine loads.

 

I will try to get a video of it today.

 

Now, if I were to take off 50% throttle or more, and right before it shifts, I let off and back on, and off, i can rev the engine very easily. Feels/sounds like no load/neutral type of revs. Once i pick a throttle position, it will go. If its a lower rpm, it is smooth. If I do it at a higher rpm, it picks the same gear, but its gonna chirp the tires. I dont know other then the fundamentals of the automatic but my assumption is causing the clutch packs to be disengaged and engaged quickly. I really dont know though.

[Doug_Scott]

The condition I described could also be described as behaving just like it would if you drove the truck at 10 mph, put the truck in neutral and raised engine rpm to 2500, then drop it in drive. My truck does the freewheeling/engine flareup on slow corners as well. I have found that going a couple of mph faster will prevent the trans from downshifting to low gear. Do not recall it doing that before the blackbear tune, but then again the tune was done about 4 months after buying truck new.