Archived 1-2 upshift hunting

[jaybo]

My '99 47RE transmission hunts back and forth between 1st and 2nd on upshift during light to normal accelleration. It jumps back to 1st then 2nd then 1st then finally shifts to second. On harder accelleration it upshifts normally albeit at higher mph. Adjusting the kickdown cable seem to move the mph shift points but does not seem to affect the hunting. As the truck warms up to normal temperature, the problem alleviates to 1 or no hunts.



Working Conditions,

New ATF4 and filter, front and rear bands are adjusted to spec; Trans is low wear. Problem seems less severe with 1 qt. extra fluid. All other shifts are fine. Since trans attempts to upshift at the same mph consistently with simliar throttle settings I have ruled out the governor pressure solenoid. My modified valve body allows lockup in 1 and 2 and I am sure the bands are not slipping.



Any ideas? Stuck 1-2 valve? VSS? The valve controls the actual shift and I use very high line pressure. The PCM inputs and outputs control the shift timing.



My main transmission brain resource, Tony Garcin, passed away. Does anyone have contact information for Bill Kondolay?

 

[FourBarR]

bill konolay www.dieseltrans .com

 

[jaybo]

Thanks... I'll call him.

 

[jaybo]

Took it to a trans shop. Governor pressure sensor not working... The bad news, I need a rebuild because the rear band is dragging and I have too much deposited carbon in the pan...

 

[Sticks]

Now, I'm no auto transmission expert, but if the fluid was not burnt, and there is no metal accumulation in the pan or high metal content in the oil (have a sample tested)... I'd be looking for a second opinion.

 

[DieselLady]

Ya I kind of agree. I see the gray goop in the bottom of the pan all the time. Normal wear. You may want to check your second gear band adjustment as well. That band applys second gear. Could be slipping.

 

[jaybo]

The amount of gray material in the pan is 4x normal. The rear band has less than 1/8" of play on the apply lever and the adjustment bolt is near the end of its adjustment range. The front band was ok; Both were normal at 1/4" three months ago when I changed the fluid and filter. At that change there was only minor gray material in the pan after a 15,000 mile interval.

We believe the rear band is near wear out because of something being bent like a pin we can't see. This has caused the band to drag.

The upshifting problem is because of a defective governor pressure solenoid which we can see my monitoring the PCM with a scan tool. This is probably because of the very high line pressure I use to keep the TC lockup clutch engaged at full power.

The trans is a stock lineup with 97,000 on it. It has had a full lockup valve body and a single clutch Suncoast TC since 2000, and is mostly used to tow a 15K 5er.

I have decided to rebuild the lineup with DTT components (as should have been done long ago) before the case gets too much wear. I will go to a Georend 3x TC with a 1900 rpm stall speed. This should allow a moderate reduction in line pressures which will smooth the shifting somewhat. The 2-3 upshift has always been very abrupt and this contributes to band wear.

I will inspect the flexplate and input shaft after we pull the trans. but will probably use stock replacements if required to save $ since I don't pull sleds and produce only 325 HP.

 

[DieselLady]

Hummm, sounds like you got it diagnosed. ")

 

[cerberusiam]

The rear servo likely turned sideways and jammed in the bore causing the band to drag. Those need replacing with billet versions so alleviate that failure point.

 

[jaybo]

hunting problem was caused by a bad governor pressure solenoid. Solenoid was bad because of excess material in fluid due to dragging rear band. I had it adjusted too tight.

Overhauled transmission (97K miles). Found overheated rear band and drum, one burned clutch plate in the direct clutch, otherwise not bad. It wasn't holding pressure well due to aging seals. $4200 later with DTT billet parts and all billet except shafts, it works pretty good. Used a Goerend TC; like the firm lockup altho the coupling is a taste loose on the "1700-2000" stall model.

 

[Sticks]

Tough lesson to learn.

Glad you got her fixed, but $4200... OUCH.

 

[Joe Mc]

$4200 with everything he's done ain't that bad considering "you get what you pay for" and with DTT (or any of the other big names) you do it once and if built to "how you intend to use it" it will last 10Xs longer and put the power to the ground more so than the $2000 - 3000 you might pay a local trans shop to "rebuild" it.

MHO of course - going on 9 years w/my DTT, courtesy of Tim Barber of TRE Diesel Performance, Virginia Beach, VA Home Page Good People!