Allison 5sp: Harsh shifts sometimes?

[THEFERMANATOR]

I'm running into an issue with my BURB here as of late and I have an idea what I think it is, but want to ask those who know alot more than me first. I'm having issues with my trans shifting REALLY hard when cold and the 2-3 and 4-5 shift being harsh when warm and occasionally I will get a NASTY 4-3 downshift. This isn't all the time and you can't predict when it will happen, and has no pattern to it whatsoever. Origanally this tsrted off as a semi-harsh 3-2 downshift, but that doesn't happen hardly at all now but then the 2-3 shift got harsher and now the 4-5 is getting to where it will clunk at times. I can clear the taps and it will come right back as soon as it adapts again, but if I do a full flash of the TCM and clear the TAPS it will go away for a week or so. It doesn't seem to matter if I'm running a stock tune or not, but I'm getting ready to full flash in all stock tunes to rule that out. I've pulled the valve body and checked the trim valves and all the valves in it and they all moved freely and there is virtually no signs of clutch material in the pan after 7K miles.

I don't have any logs of it, but I have watched it with the V2 during the shifts and I noticed when it would shift harsh the defuel would actually take place after the shift was done, and it would barely defuel any(maybe 2-3MM3 of fuel would get pulled). I never had any shifting issues except for the 3-4 after it had sat for a little while until I changed my TCM out. Since then it has been doing some wierd things at randomn, but has gotten much more frequent now. I'm trying to find another TCM to try, but I've already used my VIN license up on this TCM. I didn't know if maybe a pressure manifold could be going out and cause this as all of my problems seem to involve the C3 clutch in some way shape or form.

Any help is appreciated.

 

[stacks04]

i would full flash the stock tunes into it again. then let it learn see if it comes back. i know for a while i had some really weird things going on with mine, only with my bigger tunes. i finally figured it out with to much fueling in lower ranges. they all but disappeared since i made the appropriate changes. thing shifts really smooth now.

 

[THEFERMANATOR]

I've tried to keep everything below 50% throttle and 30MM3 of fuel stock. What is wierd is it will never do these hard funky shifts when I get on the throttle, when I baby it it shifts this way.

 

[stacks04]

mine was the same way. flash it back stock and see if it is the tuning or not. then scratch your head. i used to go with the 30mm3 and below, now i dont change fueling alot below 40-50mm3 and 100 mpa. i really concentrate on the lower right section of the table. same with the throttle based tables. my race tune i have now is awesome shifting and really streetable.

 

[THEFERMANATOR]

Well going back stock opened up some other issues and the origanal ones still seem to be there. I flashed in a completely stock 01 TCM OS, and an 01 ECM OS with a few changes that I have to make due to the swap. I still get a slight lunge on the 2-3 shift and the 4-3 seems to be consistently harsh now whereas before it was only when cold. It still will only defuel part of the time, but now it will do it in all the upshifts. Also now I'm getting a HUGE flare on the 2-3 if I give it any throttle to speak of and doesn't seem to be adapting to it at all. This is what has me puzzled is you can't ever nail it down as to what it is going to do. I hate to but I'm about ready to yank the trans and see what is going on inside of it. I've pulled the valve body and all the clutch packs you can get to from in that area seem fine with good clearances, and I have virtually no clutch material in the pan after 9K miles. I've changed the spin on filter now probably 4 or 5 times and that never seems to change it either. Hopefully I can pick up another TCM to try out and see if that is it as all my funky shifts started with this TCM.

 

[THEFERMANATOR]

Well the 4-3 downshift seems to have calmed down some, but the 2-3 harsh shift and the delayed de-fuel is back now after less than a week. This was with a stock tune, and I also tryed a very well known box tuner. The harshness seems to be the same with all of the tunes I have tried now, and it honestly feels like the de-fuel is happening after the shift to 3rd is done. Still trying to find a TCM to swap in so I can see if that is it.

 

[THEFERMANATOR]

Well I don't know if it's fixed or not, but on Mike L's advice I swapped out the solonoids and pressure switch in it. While I was in there I checked all of the shift valves and found the C valve to be sticking bad when it was stroked far enough to open the shift passages, the main control valve also had a burr on it, the main control relief valve was REALLY hard to get out due to a burr, and the F trim valve was a bit sticky in the bore. The other TCM I tried did some wierd things as well, some the same as this one and some new ones. So far I have noticed that ALL of the shifts have changed DRASTICALLY. All of the shifts seem to be much crisper and faster now. I still get a slightly nasty 3-4 for the first one after sitting, but it isn't as bad as it used to be. And now the 3-4 is quick and fast after driving it whereas before it was long and drawn out. It still shifts a bit hard when cold, but seems to smooth out a bunch when it gets up to temp. I'm going to drive it awhile and see how it does, but if it stays like this I can live with it.

 

[THEFERMANATOR]

Well it's been almost 3 weeks now and the shifting seems to be very consistent now. The 3-4 shift is a bit firm, but with 7 C2's and no wave plate I think that is to be expected. The one thing I have noticed is that the trans seems to run about 20 or so degrees warmer than it did before, but it hasn't crossed 200 yet even towing in 90 degree heat with the A/C on and runing the SNOT out of it. So even though they aren't throwing any codes, don't assume the solonoids are good.