Auto trans over rev's when shifting

[vdub]

Maybe you guys can tell me if this is normal behavior. I have an '05 with the auto 48RE trans. When pulling a load (10k) up a steep hill, the engine seems to momentarily over rev just after the trans shifts down a gear. It normally shifts at about 1500 rpm. After shifting, the rpm's go up to about 2600, then settle down to about 2000 or 2300 when it finally "grabs". Is this normal? Is it just the torque converter locking in? I asked the dealer about it and his comment was "don't worry, just get in and drive the heck out of it". But I tend to like to know what is going on, so that wasn't a good answer IMHO. Maybe one of you can shed some light on the subject.



BTW, small hi-jack... anyone know the latest status of an e-brake for the 48RE? I understand a part number has been issued, but the part is not available. Supposedly I am on a list a Dave Smith's to be called when it is available.

 

[BHolm]

If you use tow/haul mode you should see less of this behavior as the trans will make upshifts with the convertor locked for 2-3 and 3-4 shifts. Yes, what you are experiencing is normal operation. The shift takes place with the convertor unlocked for a smoother shift, then locks up to transfer the power more efficiently. I think I would add a transmission temp gauge if you tow on big hills a lot. Do not count on the factory idiot light, by then it is too late.

 

[vdub]

Thanks, for the advice. Good to know that it is normal behavior. And, I was figuring on relying on the idiot light. But since I do live in hilly country, I think I will invest in a trans temp gauge. I can not leave my home without ascending at least one 6%+, 8 mile grade. Depends on which direction I head. If I go south, then I have 3 grades to go up and down -- each about 6% and each about 8-9 miles. That's also the reason I'm wanting to get an e-brake for the rig. Thanks for the tip!

 

[Cummins Thunder]

Thanks, for the advice. Good to know that it is normal behavior. And, I was figuring on relying on the idiot light. But since I do live in hilly country, I think I will invest in a trans temp gauge. I can not leave my home without ascending at least one 6%+, 8 mile grade. Depends on which direction I head. If I go south, then I have 3 grades to go up and down -- each about 6% and each about 8-9 miles. That's also the reason I'm wanting to get an e-brake for the rig. Thanks for the tip!

GET THE GAUGE!! Kind of off topic but... A good friend just killed his trans by over heating it Couple of months ago we installed gauges in his truck, but what gauge did we leave out?? yep, the trans temp! Need less to say we now have one on order from Summit, along with a few other goodies to fix the transmission.



CJ

 

[vdub]

Any recommendations on which one and where the best location for the sensor is?

 

[Caveman]

vdub,

I just had my 48RE in my 04. 5 rebuilt by the dealer. I was experiencing the same issue. It got to the point I had to downshift from D and back to get it to go into 3rd. They replaced the drum, clutch packs and torque converter. If you drain the trans fluid and find gritty stuff along with the shavings you need to take your truck into the dealer. I even had a Mag Hytec DD pan with synthetic oil to keep the thing cool.

 

[vdub]

That doesn't sound very encouraging. I have about 5k on the rig now the dealer is giving me my first oil change free, so maybe I'll have them check when I take it in. Fortunately, the dealer is at the base of 6. 5%, 8 mile long grade, so testing should be easy.