4R55E sluggish 1-2 upshift

[holter95]

Hey all - long time no see.

Looking for advice on my 95 EB 4x4, 4-spd. My 1-2 upshift has become very soft, almost imperceptible under almost every load. Very reminiscent of a CVT (you can't tell it's shifting - I have become acclimated as I'm working on the D258/219 program in Chicago, and have lotsa CVT exposure). Looking for potential issues that may be causing this.

Vehicle has 208K miles, trans was R&R'd (factory reman) at 78K miles. Since, I've done trans fluid/filter flush every 25K-30K miles. Fluid looks and smells OK (no evident burning). All other gears upshift/downshift fine, OD is functional (although switch is broken), and TC seems to lock/unlock normally.

No Check Engine/Trans lights to speak of on this. Only other fault that would correlate I could think of is that I recently had the vehicle stall twice during rolling stops (potentially during a 1-2 or 2-1 shift), but the engine may have been suffering other ailments as the car sat for about 2 months prior to this.

Thoughts? Sticking valves? Solenoids? Maybe a malfunctioning TC?

On the same note - anybody know of any reputable tranny shops in the Detroit Metro area?

Thanks in advance!
Holter95

 

[Glacier991]

Man tough Q. Most likely either a partially plugged solenoid or low line pressure.... Since I have discovered the transmission pressure gauge I am probably a little too focused on it.... soft shifts usually mean restrictions in pucks, solenoids or other areas, or a myriad of other things... This is gonna be a tough call without more info.

 

[holter95]

it all went downhill fast

Well, the original problem was a failing (sticky) 2nd gear shift solenoid. $200 later, I was back on the road... for about 20 minutes when a band snapped in 2nd gear, warranting a full rebuild. Luckily, the guys at the trans shop credited me about half of the labor done, and proceeded with the rebuild.

Once the rebuild was complete, I drove it home, and the next day on the way to work, it began shifting very hard, and lost second gear halfway to work. Limping it down to the trans shop during lunch, I lost reverse, O/D, 2nd gear came and went, and had 2 occasions of the TC failing to lock up, leaving me spinning going up a slight grade.

What appeared to happen was a faulty pump regulator, which ended up starving the trans for adequate pressure. What actually caused the failure is unknown though (contamination, or damaged component). Unfortunately, it did enough damage to warrant another complete rebuild, but fortunately the shop honored their 1-year warranty and did it gratis.

Crossing my fingers that this is the last I've seen of the guys at the shop (I'm sure they're hoping the same!)