I'm not sure if it is a problem or not, or if I am just feeling something weird.

Every once in a while, when I step on teh go pedal hard, the trans downshifts as it should, but then doesn't seem to "catch". The RPMs go to redline and stay there as the truck accelerates (but not as hard as it should) until it upshifts, then it sets you back in the seat as normal.

I'm not sure if it is just downshifting to a lower gear (2nd maybe) when the vehicle is moving too fast and it is redlining in 2nd, or if the trans is slipping.

All I have on it is a Hypertech programmer that I run in level 2 of 3 all the time, and it has about 70,000 miles on it. I have had the trans serviced once since I got it used with about 35,000 miles on the odometer. I tow a 5th wheel RV that weighs about 11,500# during the summer. No shifting issues when towing, but then I rarely floor it at low speeds when towing.

Truck is out of powertrain warranty. I plan to take it to a local transmission shop for a service here soon and see what they think.

What do you guys think?

 

Sounds like the TC slipping...

 

Sometimes I think mine does the same thing... I have decided that its just the trans. control and engine control trying to figure out what each other is doing.
I watched my boost one day when it seemed to do it and the boost didnt come up as quick as normal.

 

Possible front band is worn or shot....

Front band applys during downshift to second..if its worn it wont slow the drum down fast enough and youll get the condition you refer too.


Might try a band adjustment on BOTH bands and see if that helps at all.

Youll really only notice TC slip when its locked...during a DS the converter is unlocked.

 

Mine was the front band just needed adjusted. But I think it starting to do it again.

 

Mine has done this since it was new. Mine at least just shifts down to far and red lines for a second and then shifts up and goes. It only happens when you accelerate hard such as passing. It sounds like your trans is doing the same thing. If it was slipping it wouldn't accelerate so hard after it shifts up. I wish it wouldn't do this, but still love the truck.

 

Ok, thanks guys, sounds like the front band needs to be adjusted. The trans service I got was at the dealer when they did the TSB for the 1-2 shuttle shift. I suspect that since they had to drop the pan anyway, they just threw in 6L of ATF+4 and a new filter and didn't touch the band adjusting bolts, since you need an inch pound tq wrench and all.

I think it was one of those "no point in putting the old fluid back in it, and I may as well put a new filter in" rather than "I'm gooing to give this guy a free trans service while I'm in here" kind of things.

I will mention this to the trans shop when I take it in.

Thanks all.

 

Are you telling us the dealer did not have a torque wrench that was in inch-pounds? If so, I wouldn't let them anywhere near my truck!

 

No, I just think they didn't bother to do the whole routine for the trans service because it's not what they were in there for. The truck was in for the shuttle shift TSB, and they just decided to replace the fluid and filter while they were in there (warranty). The trans service is of course not warranty work.

 

Do a search on governor pressure sensor/transducer and governor pressure solenoid. Lots of posts on this. I had this same problem and replacing both parts fixed the problem for me. I had the bands adjusted prior to this and it did nothing for the problem. Common issue for the 48re trans and I think there are available upgraded after market parts for this issue. I just replaced with oem parts and it took care of it but I will probably end up replacing them again in the future because they are known to fail over time.

Good Luck,
Sticky

 

OK, that makes me feel better. Thanks.