Odd trans behavior

[Bako_Dmax]

The last 2 days my allison has been doing some strange things. When I first drive my truck to trans works perfectly no matter how I drive cruising or hammering it. If I drive the truck in traffic long enough to where the temps reach 185-190 the truck will have a huge flare between 1st and 2nd, then when I slow to a stop the truck will jump around a bit like it doesnt know what gear to be in. Then if I take off again it will either flare again, or not shift out of first. Also when I will slow down when it starts acting up the trans feels like it will bind up sometimes, like two gears are being engaged at once.

As soon as I let the trans cool back down it will shift flawless until it reaches those temps.

The codes It has shown are: p0777 p0776 and it threw p0732 once, they never all come up at once its either one or the other.

I changed the spin on didnt help, I cleaned the main harness connector and that didnt do anything either.

Oh and when it decides not to shift out of gear the engine will rev up and down pulsating on its own sometimes..

 

[Mike L.]

Your C2 clutches are probably gone along with the C2's if a spin on didn't fix it.

 

[Bako_Dmax]

Really? Is there anything else thats a possiblilty? I can load up a 500hp tune and hammer the crap out of it and it will click off shifts perfectly until it reachs 190*. To be more specific on the flare up part its not a slipping flare its like the truck is in neutral and will slam into second. when I changed the spin on the only thing open was auto zone so I put one of those white spin ons on there, fleet I think. I changed the filter to an allison today and changed the fluid also. The old stuff wasnt burnt or discolored. I just drove it to the store and it was shifting perfect but only reached 170* or so.

Any other thoughts on this? Maybe the pan filter?

 

[Bako_Dmax]

Update: I just drove it around hotrodded a little got the trans temps up to 190* and no problems. Maybe that spin from auto zone was junk? Or something else completly random. Ideas?

Thanks for your time Mike.:hug:

 

[MACKIN]

Really? Is there anything else thats a possiblilty? I can load up a 500hp tune and hammer the crap out of it and it will click off shifts perfectly until it reachs 190*. To be more specific on the flare up part its not a slipping flare its like the truck is in neutral and will slam into second. when I changed the spin on the only thing open was auto zone so I put one of those white spin ons on there, fleet I think. I changed the filter to an allison today and changed the fluid also. The old stuff wasnt burnt or discolored. I just drove it to the store and it was shifting perfect but only reached 170* or so.

Any other thoughts on this? Maybe the pan filter?

Shot in the dark here,

But perhaps you are your own worst enemy.

You say:you load a 500 HP tune and it shifts great.

Two things come to mind here. Transmission shifting characteristics change once fluid temperatures rise . Also PERHAPS your BIGGER tunes are playing games with your shift issues.

Go back to the drawing boards or use the tune that works best until you figure it out by comparing your tunes.

Good luck in any event!

 

[Bako_Dmax]

So my ecm tunes could be playing games with my trans shifting once the temps reach a certain level? Ill try some different tunes and see what I find out.

 

[Mike L.]

Be vewwy vewwy afwaid of P0776. If you keep hammering it before fixing it it will cost big time.

 

[LarryJewell]

What does P0776 mean

 

[Mike L.]

What does P0776 mean

Massive tie up on the 3/4 shift usually destroying C2 clutches if your lucky. If you're not; P2 planet and C2 hub.

 

[beach_33]

so what would the cause of a tie up here be.

 

[Mike L.]

so what would the cause of a tie up here be.

Could be a lot of things. TCM or ECM tuning, wrong clutch clearence, too many clutches in the wrong place.

 

[MACKIN]

so what would the cause of a tie up here be.

I wish I could tell you exactly but I cannot as EFI is out of my realm but I do know that you can cause a tie up in a shift with ECM and TCM tuning.

Best advice I can give you is compare your tunes by logging some driving with what works and what doesn't. You should find the answer there.


Sorry I cannot be of more help. Other than to tell you where to look

 

[MACKIN]

Could be a lot of things. TCM or ECM tuning, wrong clutch clearence, too many clutches in the wrong place.

Guess I should have not went and smoked that butt

 

[RENODMAX]

Even when you have weird shifting problems with ECM tuning the trans wont usually throw codes. Id listen to Mike on this. I know you built your own trans so you might wanna pull it out and check stuff out before you wreck some hard parts if any damage is happening.

 

[mytmousemalibu]

Mike...What could be changed in the "ECM" tuning that would cause tie-up? I just wanna know so i can avoid doing it! :hug:

 

[Mike L.]

Mike...What could be changed in the "ECM" tuning that would cause tie-up? I just wanna know so i can avoid doing it! :hug:

Fueling before, during, and after a shift occurs. Be carefull of tunes in libraries at certain forums. I trust the tunes here. There are some so called famous tuners out there that don't know shit and will distroy your trans.
Check out who the tuner is and what he tuned. Does he race his duramax?

 

[IdahoRob]

Fueling before, during, and after a shift occurs. Be carefull of tunes in libraries at certain forums. I trust the tunes here. There are some so called famous tuners out there that don't know shit and will distroy your trans.
Check out who the tuner is and what he tuned. Does he race his duramax?

I race my Duramax:hug:

 

[JoshH]

Really? I don't

 

[Kat]

Really? I don't

You will again soon

 

[Bako_Dmax]

Well it seems to only happen with one ecm tune, I guess Ill toss that one. Thanks for the input fellas.