Towing Heavy Transmission Temps

donjetman said:

Just some thoughts I had:

I've owned a few 40K to 50K # motorhomes with 11L & 12.7L diesel engines and Allison 6 speed autos. The rule to keep them from getting hot is "keep the rpm up. Don't lug em." I don't know if the same applies to gasoline engines.

For many yrs I've been doing used ATF analysis with some of my vehicles. My ATF samples I send to JG Lubricant Services because a President/owner, x GM fluid engineer Tom Johnson, is at ph 877-971-7799 ext#2 to answer question(s). I've talked to him several times. Give him a call. Nice man.

IIRC, Tom says your Dexron6 atf tempsaren't hurting a thing. Prolonged temp greater than 235 and the fluid starts to degrade.

If your worried about Dexron6 viscosity thinning out, you might consider running an Allison approved TES668 atf. They have a higher viscosity. Some Corvette folks that "track" their car do it.

You might consider ordering some kits too so you can see what is what.

https://www.jglubricantservices.com/docs/Technical Information Sheet.pdf

https://www.allisontransmission.com/parts-service/approved-fluids/on-highway-fluids

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mikez71 said:

There is a dedicated channel that is PE active or inactive that should show up...

I always thought the PE was like an accelerator pump, but watching one of these youtube tuning videos, apparently it is for cylinder cooling when you are heavy on throtte/load.

Or the HOT table for PE, which seems to be set at 87% throttle from factory. Perhaps you're over 87% in 5th, but under in 4th.



I hope so! (they are going into 5th gear...)

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j91z28d1 said:

pe is performance enrichment mode. you're thinking of AE acceleration enrichment. that is like carb pump shot for wall wetting in a port or wet induction setup. there's also a DE for when you let off the throttle it cuts fuel for the wall fuel to evaporate. some good sae papers used to be available online for this.

in pe mode is when you need something other than close loop 14.7 target fuel. so makes sense there's a high temp activated settings too, like there's cat over temp math that will flood the cats with extra fuel to cool them down when the math temp says they are at risk of melting. like say a track day or I'd guess towing even, which is a bit weird because cats run hotter the richer the mixture, which is why long time is pe mode can melt cats since you're stock tune can be as rich as 11s a/f at wot. but I guess if you dump even more fuel in them, they cool back down again. most tuners turn cot off first thing.

the other thing I do wonder, having raised pe enable to above what it would active at stock and then towing heavy up a mountain in closed loop 14s at 30plus deg timing. that seems to be asking a lot? I have not idea the actual load in the engine but I'm picturing 3/4 throttle?

would giving up a little mpg to allow pe mode to get you down into the 12s a/f be better over all? any idea what a stock tune would run at that load point?

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j91z28d1 said:

normal being 14.7 ish e10 changes that some but generally. would it be in pe mode running richer at that point normally? that was my curiosity, say 12.5/1?


load doesn't sound as high as I was thinking. for hptuners you'd probably have to screen capture and then save it as a jpeg to upload it here.

might be more telling if you can upload your stock read as a compare in hp, and see how different they are at the spot you'd be in on the map at that time. but you're right, the cam and free flowing exhaust changes it all some.

in my generally experience that's pretty limited, ls engine don't normally need as much timing advance as old small block, those needed all the timing they could take to make power. ls seemed more forgiving to conservative timing

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Foggy said:

Unfortunately my OE stock read is long gone.. in 2020...
Then when I removed the SC in favor of a vvt cam and mild head work
The new tuner I used told me they couldn't tune it because I had bad pistons
from the SC being on it (********)...
It just ended up being 1 bad coil pack .. I told them I had the heads off. All was perfect.
So then I just decided to learn to tune on my own...
It's been a journey to even get to this point... And 3 times I've paid for credits
for the same Yukon !
Anyway, I got rid of the virtual flex fuel BS and since it's all E10 with best
octane of 91 in my area.. I have set the AFR target to 14.30 ish to compensate.

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j91z28d1 said:

it would be cool to see what other guys that tow have for tunes either stock or what someone like black bear has setup. of they would be willing to share info with you.

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j91z28d1 said:

interesting. sounds like you got a handle on it pretty well really. it's just my curiosity as to if a stock tune would be in pe mode open loop targeting a richer a/f at that point. like you say, you're not in unsafe territory at all.

it would be cool to see what other guys that tow have for tunes either stock or what someone like black bear has setup. of they would be willing to share info with you.


but yes, these days it's my understanding you really never flash a new tune from another file. all you really do is upload the other tune into compare and see what's different. if there's something you like copy and paste it into your tune and flash.

just for the heck of it.. here's a pic, hopefully it's not to blurry of my 6.0 hybrid high octane timing map and my ls3 c6 stock maps. not that you'd want to run these, just a visual of why I'm supised you're seeing 30 plus deg. 3000lb car with a ls3 doesn't even run that. and I've since pulled 2deg from this map for hard driving, it just feels smoother, might give up hp thou. I just saw it talked about somewhere, tired it and was like huh, engine seems happier so I left it out.

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mikez71 said:

I have a 2012 yukon 6.2 stock file if you need. (two from hptuners repository) both identical.

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