LLY: Transmission issue

[Mr.C]

Hello guys, I'm driving an 05 Silverado Duramax. Yesterday when dragging the 12,500# 5th wheel I got a P0735 code. It went to 4th gear and stayed there until I got it cleared. I was in tow mode also. Five miles down the road it came again. I switched out of tow mode and it never came back. Anyone have a possible reason?

 

[Chevy1925]

how about ALOT more infomation about the truck and what you have done to it

 

[Mr.C]

05 Silverado 2500HD Duramax, Allison 1000 (stock), 89k miles, Diablo Sport tuner set at 85hp, 4" exhaust, B&D Engine brake, PPE transmission cooler, AFE filter base with a K&N round filter installed. Fresh tranny fluid change at 84k to Allison Trans fluid. This truck hasn't been hot rod.

 

[Chevy1925]

transmission has had enough of the 85hp tune. the trans is limping. i suggest dropping the power back to stock, trans is hurt now. it will only be easier and easier to limp the trans from here on out even if you drop to a lower setting.

its time to start thinking about building the trans or having it rebuilt and see far you get again before it limps under that power.

 

[Mr.C]

Darn, she never went into limp mode again if I'd take it out of the tow mode. Didn't really require tow mode, there was no hills or even inclines during my short trip.

 

[Mr.C]

I couldn't make it limp today back and forth to work, but no trailer. Used tow mode and all. Any suggestions for rebuilders in the DFW area. The only connection I've had here is Inland Truck a Allison Transmission place.

 

[IOWA LLY]

Josh from top notch garage is somewhere in Texas. Can't remember the exact area but he is definitely where I would take it if your in Texas.

On edit he is in Van Texas.


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[Mike L.]

When the Allison is in tow mode; pressure drops 100 psi. That means less holding power for the clutches. Don't be fooled by the fact that it shifts more firmly.

 

[Vmyrhaug]

So, its not recomended too use tow mode? That's why my trans is limping in tow mode! Is it possible to increase pressure in tow mode? I use tow mode because of lock up in lower gears...

 

[hondarider552]

Just turn the power down to stock or level one from here on out.

 

[prostreeter600]

So Mike I’m confused, I was always told that when I race my truck or launch it hard, it should be in tow haul mode . I thought there was more line pressure being applied in tow haul mode . So am I better off racing it in Drive ?

 

[Mike L.]

So Mike I’m confused, I was always told that when I race my truck or launch it hard, it should be in tow haul mode . I thought there was more line pressure being applied in tow haul mode . So am I better off racing it in Drive ?

It doesn't matter on a stock trans. Anytime the converter locks it drops pressure. The only way around that is a built trans properly set up.

 

[prostreeter600]

I see

 

[Woodster]

Can we sticky this? :roflmao:

 

[jlawles2]

When the Allison is in tow mode; pressure drops 100 psi. That means less holding power for the clutches. Don't be fooled by the fact that it shifts more firmly.

Why would dropping the line pressure in Tow Haul mode be done?

With my basic understanding of automatic transmissions, it seems that you would want more holding power to the clutches under higher loads. Did the Allison engineers expect to have hard part problems if they either kept the pressure or increased it?

 

[IOWA LLY]

Less line pressure equals less heat, less drag, and less seal ring wear.

The Allison engineers built it to handle stock horsepower and torque number. And they do that just fine.


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[Mike L.]

Better mileage also.

 

[jlawles2]

Thanks for the information. Make sense as to why.