Allison 5sp: 3-4 shift harsh sometimes

[THEFERMANATOR]

Over the last couple of months my BURB has gotten to where the 3-4 shift will bang when it goes in sometimes to point that I can't ignore it anymore. It has always done it slightly, but now it has gotten to the point of being BAD. The thing is it isn't always bad. If I pull in and get diesel or something and put it in park(doesn't matter if I shut it off or not), after about 5 or 10 minutes I take back off and accelerate easy on it the 3-4 shift will slam in HARD. The wierd part is I can immediately slow down and go back to 3rd, then the next 3-4 will be silky smooth and every 3-4 shift afterwards so long as I don't take itout of gear will be smooth. If I take off after being in park for a few minutes and give it say half throttle though the 3-4 won't bang at all, just a tad crisp. If I drive around for a few miles in 3rd(like in tow/haul mode) before the first 3-4 after being in park, it won't bang hardly at all either(the longer I drive in 3rd the better the 3-4 will be). I have been out in the woods with it and idled around in 1st and 2nd for an hour before, take off back down the road and the 3-4 will be perfect so long as I never take it out of gear. Doesn't matter if I'm in T/H mode or regular mode.

The 2-3 shift in thing is also a bit faster than I think it should be when I baby it, but is nice when I get on it. I have tried an 01 OS(the best shifting of them, but the WORST for the harsh 3-4), an 02, and 03-04(the absolute worst shifting OS I have ran, can't ever make its mind how its going to shift). I've also tryed 2 different TCM's(my spare is a known good unit with an 03 OS in it), and it still does the same exact thing with it in. I've pretty well come to the conclusion I need to pull the trans, but where should I look inside of it for this issue? Spin on is good with less than 2K miles on it, transynd fluid that doesn't show much clutch material in it, never ran a big tune on it(maybe 400RWHP at the most), and the solonoids were replaced with no correction to this issue.

 

[Mike L.]

If you're running 8 clutches in C2 that is a big mistake as it creates the worlds biggest tie up on the 3/4 shift. 6 frictions with a wave plate will take the harshness away. You may also have a tuning problem, but you won't know till you fix the trans.

 

[THEFERMANATOR]

7 clutches with no wave plate in the C2. Tuning has no effect on it either as 3 different TCM tunes with 2 different TCM's, and several engine tunes ranging from stock to moderate ALL do it the same. It just makes no sense to me how it will only do it after it has been out of gear for 5 minutes or so and you immediately go through the gears. After it makes the first 3-4 shift, the rest will all be perfect.

 

[THEFERMANATOR]

Finally got inside the trans today to do the autopsy, and it isn't horrible but not good either. The C2 clutches have quite a bit of wear in them as they are all down to about .064-.065 instead of .069 like they were when I put them in(although I measurede my left over C2 from when I built it and it was .073). Also I found surface cracks in several of the C3 and C4 steel plates. C5's look great as well as the C1's. All of the C3 and C4 clutches are still dead on in thickness even though the steels show quite a bit of wear. I believe I found my 3-4 shift problem though, and I hate to admit it was my own fault. When I tore it down I found a piece of a terry towel(just a small lint like strand) was lodged inside of one of the C2 piston bleed holes in the orifice plugs that you put in with the TRANSGO kit. So only one bleed hole was working. Also I found that the bottom of the C1 apply piston just below the seal was gouged up pretty badly and it gouged up the inside of the C1 clutch housing.

I haven't made it to the valve body yet, so I hope it's alright. My main concern is there was quite a bit of clutch material in the oil I drained from it, and I think there is more in the oil than is missiong from the C2's. So it looks like I need to send the torque converter out and have it checked while it's out.

 

[THEFERMANATOR]

Well I have a theory on what was going on with my trans now. I picked up a SONNAX E-valve reamer just to see how my E-valve bore was. So far I haven't been able to get it in the last 3/4" through the last portion of the bore. Also when I went to remove the E-valve after it had sat for a few days, it was jammed in the bore. So best I can figure is the E-valve was sticking and when it would release I would get my harsh shift, and while there was pressure present on the valve it wasn't going all the way back in it's bore until the pressure was released off of it. Does this make any sense?

My new C2 pack and some other parts should be in tommorrow, so hopefully I'll have it going again this weekend to see if I've helped it any.

 

[5akman]

any updates on the shifting issue?

 

[THEFERMANATOR]

Yep, I put it all back together with a new C2 pack with a wave plate from SUNCOAST, replaced all the seals and gaskets again, reamed the E valve until it was as slick as could be, and had my valve body halves surfaced as I found them to be warped almosy 10 thousands in spots. Now it shifts good on everything BUT the 3-4 STILL! It has actually gotten WORSE after doing all of this as now if I get caught in traffic for a little while without going into 4th, it will be harsh going into 4th when I do another 3-4 shift which it didn't used to do. So opening the outer orifice hole up did not help it but made it worse. I have come to the conclusion that it has to be a problem with the C-2 circuit not getting backfill fluid for some reason, and I believe the trans needs to come out agin as I have an idea as to what it is(and it isn't a cheap fix either).

 

[2003 duramax]

Mine has been doing the same thing after I got it rebuilt. But I'm thinking it be because I put the stiffer spring that comes with the ppe shift kit. But I have not had time to do anything with it.

 

[Mike L.]

Mine has been doing the same thing after I got it rebuilt. But I'm thinking it be because I put the stiffer spring that comes with the ppe shift kit. But I have not had time to do anything with it.

It's the Transgo shift kit and the springs cushion the 3/4 shift. Without the spring you would rip the splines off the P2 planet and C2 hub.

 

[THEFERMANATOR]

I ahve tried a bunch of different things with mine, and currently I am running stock trim valves as I got tired of the harsh 3-4 on the initial shift. On a PPE kit I could see it being from teh kit though as they send you 8 C2 luthces and no wave plate according to there install directions. That would make for one heck of a shift as it is just more clutch material biting than you need I think. I'm trying to source out a 6 speed now to put my clutches in and swap into mine as I am tired of fooling around with this one anymore.

 

[Mike L.]

Stock trim valves won't help 3/4 shift as the C2 clutches work off of mainline pressure.

 

[THEFERMANATOR]

Stock trim valves won't help 3/4 shift as the C2 clutches work off of mainline pressure.

It definately softened mine up ALOT. The initial 3-4 shift with stock trim valves in is nice and quick and firm now instead of a clunk, but the next one will be soft and mushy. This is just one more mystery in mine that just doesn't make sense.

 

[2003 duramax]

Sorry mike l it was the tcc valve and I remember my trans builder asking me if I wanted the stiffer spring for more pressure or not. But after looking over the instictions again it says the 2003 used both springs. Could this be a problem or would the new valve even fit.

 

[Mike L.]

Sorry mike l it was the tcc valve and I remember my trans builder asking me if I wanted the stiffer spring for more pressure or not. But after looking over the instictions again it says the 2003 used both springs. Could this be a problem or would the new valve even fit.

The Transgo valve uses only one spring. It gives you a choice. You cannot use both.

 

[THEFERMANATOR]

Well I haven't quit working on trying to solve this problem, and I have finally made some headway in the right direction. Without a doubt my 3-4 shift is due to air being trapped in the C-2 fill circuit and it rapidly bleeding out and then engaging the C-2 clutches on the first 3-4 shift. So far I have tried 3 differrent valve bodies with no change. Stock trim valves do lessen the initial hit slightly, but the shifts afterwards are less than desireable. I ran a 6 speed C1/C2 drum in it for awhile, but even it did it pretty badly when hot. Right now I'm running the 03+ overlapping sealing rings, an 01 C2 piston with the .040 orifice in it but with the 2 balance ports plugged solid, and a C2 balance piston with 4 1/16" holes in it so it has zero effect on the C-2 application. this set-up gave me the best shift I found early on, but I took it a step furthur to narrow down the initial hit.

Last week I opened her up to remove teh 6 speed housing and go back to the set-up listed. While I was in there I took some aluminum epoxy and reduced the C-2 circuit cavity in the bellhousing by about half by reducing it's depth from .825" down to about .400" which drops it by about half. I also filled the C-2 cavity in the trans case down to about a half as well. these changes still allow the circuit to fully flow, but reduce the cavity volume that can fill with air. By doing this the 3-4 initial shift now has about half the shift time to it as before. Even hot the initial 3-4 shift is no where near as violent as previous set-up's I have used. the only conclusion I can come to from my work so far is that the C-2 circuit is only being prefilled by bleed over from the C-1 circuit at the drum support through the sealing rings bleed hole. Since it is being filled from the top down, the air can't be fully purged out. When the C-2 clutches are applied the air is rapidly purged out. So this delay prevents the C-2's from coming on gradually but instead the yrapidly hit when teh air purges and the pressure spike hits.

I wished now I would have tried the butt style sealing rings in it to see what that would have done for it as the reduction in bleed over from the C-1 may allow the C-2 to fill from the bottom up instead of from the top down.

 

[5akman]

Wow! Is this just a fluke with your tranny or the 01's in general? I have an 01 that had a rough 3-4 shift, had it rebuilt by Mike and it now has a 2-3 hard flare. I've checked the external wiring harness continuity, replaced ECM/TCM with SoCal units, replaced internal wiring harness as it was leaking through the connector and ohmed all the solenoids. Everything checks out fine but I can't drive the damn truck harder than about 1/4 throttle. I wasn't paying attention the other day and pulled out in front of someone, I accelerated at about 50% pedal and the 2-3 shift had me wondering where my head had landed and how many hard parts were left in the street. I'm at a loss with where to go next and have no experience to do anything like what you're attempting so that's out of the question. Right now I'm trying to find another pull out tranny to swap in for a day to see if its my tranny or so other component under the hood causing the problem.

 

[IOWA LLY]

Wow! Is this just a fluke with your tranny or the 01's in general? I have an 01 that had a rough 3-4 shift, had it rebuilt by Mike and it now has a 2-3 hard flare. I've checked the external wiring harness continuity, replaced ECM/TCM with SoCal units, replaced internal wiring harness as it was leaking through the connector and ohmed all the solenoids. Everything checks out fine but I can't drive the damn truck harder than about 1/4 throttle. I wasn't paying attention the other day and pulled out in front of someone, I accelerated at about 50% pedal and the 2-3 shift had me wondering where my head had landed and how many hard parts were left in the street. I'm at a loss with where to go next and have no experience to do anything like what you're attempting so that's out of the question. Right now I'm trying to find another pull out tranny to swap in for a day to see if its my tranny or so other component under the hood causing the problem.

You need to get in touch with your builder. Something is wrong with your trans.

 

[Mike L.]

Wow! Is this just a fluke with your tranny or the 01's in general? I have an 01 that had a rough 3-4 shift, had it rebuilt by Mike and it now has a 2-3 hard flare. I've checked the external wiring harness continuity, replaced ECM/TCM with SoCal units, replaced internal wiring harness as it was leaking through the connector and ohmed all the solenoids. Everything checks out fine but I can't drive the damn truck harder than about 1/4 throttle. I wasn't paying attention the other day and pulled out in front of someone, I accelerated at about 50% pedal and the 2-3 shift had me wondering where my head had landed and how many hard parts were left in the street. I'm at a loss with where to go next and have no experience to do anything like what you're attempting so that's out of the question. Right now I'm trying to find another pull out tranny to swap in for a day to see if its my tranny or so other component under the hood causing the problem.

Think you're up to switching a valve body?

 

[5akman]

Yes, switching out a valve body would be no problem. That doesn't scare me but digging into the tranny like Thefermanator had to do is beyond me.

How do I go about purchasing a valve body? Is that a dealer item or aftermarket?

thanks Mike!

Lance

 

[Mike L.]

Yes, switching out a valve body would be no problem. That doesn't scare me but digging into the tranny like Thefermanator had to do is beyond me.

How do I go about purchasing a valve body? Is that a dealer item or aftermarket?

thanks Mike!

Lance

I can send you one but I need the old one back asap.