New LML Allison

[moss6]

After near 1000 miles on the new 2011 the revamped Allison is proving to be somewhat of a mystery to me. The transmission shifts are more seamless than on the 06 as advertized and power transmission; I have just a gut feel, is just less power consumptive. Some early dyno results would reinforce that unless GM has underated the new LML powerplant.
What has me quite baffled is the fact that the new transmission can run so cool. Putting 465 unloaded miles on the truck for initial break in, many of which were against a substantial adverse wind and up-hill conditions, the hottest transmission temp reading I saw was 133 degrees! My first though was that the DIC was wrong, but after doing a fluid level check I found that the level was only a little over the high end of the cold level range. I also felt of the pumpkin and was amazed that it was only fairly warm, I'd guess in the 95 degree range.
Now yesterday I hooked up to the fifth wheel, which I'd say I got down the the 13,000 lb range after unloading some stuff and towed for 200 miles, some of which at the end of the run were at 70 mph and against an adverse wind of about 25 mph, and earlier were up some pretty good grades but less than 2 miles in length; the highest tempreture that I saw was 149 degrees, which would seem pretty impossible.
My only explaination would be that the thing is so strong and can lock down the packs so tight that there is just no slippage that can build up heat. My question is, how can you ever do a hot check on this new transmission?
Curious to see if others are experiencing the same thing.

[cowboywildbill]

Your right the trans on these new trucks run way cooler than before. On a hot day towing hard and heavy we only saw 152 degrees. And while stuck in stop and go 3 mph traffic for 20 minutes immediatley after pulling a long grade it only climbed up to the 170 degree range. Then when we started rolling hwy speeds again it dropped back to the 150 range almost immediatley. And the engine temp stays pretty constant while towing and runs cooler on hills also. On our 07 LBZ 200 degrees was a normal trans temp towing and up to 210+ while pulling a long grade in warm weather. I was getting 13.5 avereage mpg while towing last week on route 15 North from our Ranch to a Rodeo at 55 and 65 mph. We are getting about 1 or a tad more mpg towing with the LML and about 3 or 4 mpg better running empty. Very pleased with the truck. This LML was was like going from a 1/2 ton to a 3/4 or 1 ton truck for our heavy towing compaired to our LBZ DWR CC. What a difference in handling and braking and power. And I was very pleased with our LBZ, but these new bigger brakes and frame is definately safer. We should ask if we could get a New Column for the Fifth Generation LML trucks since they are so much different than LMM and previous generation trucks, engine and drive train wise. It's like the difference between a 3500 and a 4500 almost. LOL

[THEFERMANATOR]

The new LML ALLISON now has an electronic pressure control solonoid inside the valve body to control main line pressure like a 4L60E/4L80E uses, so your no longer running up to 250 or so PSI all the time now. And I'm sure after all the people that complained about the LBZ/LMM running warm in the trans, GM saw fit to increase the coolers capacity as well.

[moss6]

Yes the LML cooler is larger but not by much, the LBZ trans. even with the Mike L cooler was normally 50 to 60 degrees or more hotter than the new allison; phenominal to say the least. I wonder to how the rear end is staying so much cooler, must be a larger ring because of the apparently larger size of the housing--haven't measured and haven't seen anything published on it.

[cowboywildbill]

I think the new torque convertor and the tighter trans with less % of slippage and the larger cooler and maybe better engine temp control play into the lower LML's trans temps. I think a lot of the higher temps on the LBZ were due to the engine temps fluctuating and the trans cooler lines picking up heat from the radiator rather than dumping it in there. As for the rear, it is the same internally from what I've read, But the axle tubes are now 4" in diameter and larger than before to increase the wieght rating. I don't know if the larger tubes help with cooling the rear diff fluid or not. I wouldn't think so but who knows? I changed our rear diff at 1,000 miles. It only had 2.5 quarts of fluid in it. I let it sit level for a 2 hours before I drained it on a very warm day. I put just a little under 4 quarts back in and stayed the recomended 1 and 1/2 inch below the fill hole. I think the rear is the most critical first early maintance for break in that should be done. And then engine oil.

[moss6]

On the first change I always pull the cover so that I can really get all the debris out using disc break cleaner, I like that cleaner because it sprays really hard with lots of volumn.

[THEFERMANATOR]

I think the new torque convertor and the tighter trans with less % of slippage and the larger cooler and maybe better engine temp control play into the lower LML's trans temps. I think a lot of the higher temps on the LBZ were due to the engine temps fluctuating and the trans cooler lines picking up heat from the radiator rather than dumping it in there. As for the rear, it is the same internally from what I've read, But the axle tubes are now 4" in diameter and larger than before to increase the wieght rating. I don't know if the larger tubes help with cooling the rear diff fluid or not. I wouldn't think so but who knows? I changed our rear diff at 1,000 miles. It only had 2.5 quarts of fluid in it. I let it sit level for a 2 hours before I drained it on a very warm day. I put just a little under 4 quarts back in and stayed the recomended 1 and 1/2 inch below the fill hole. I think the rear is the most critical first early maintance for break in that should be done. And then engine oil.

I think the biggest drop in tranny temps with the new LML is the variable pressure control system that it now uses for line pressure. It is no longer on a fixed static control circuit that regualted it to roughly 250PSI and held it there. They can now vary from about 60 all the way up to 300 IIRC. I doubt it is any more efficient at holding engine power than a built trans, and a triple disc aftermarket converter will definately out couple anything GM puts in them. People who raise there line pressure on a built trans notice an immediate increase in trans temps. I didn't raise mine when I built my trans, and if I'm not in summertime stop and go driving it normally won't go over 130-150 even with the LB7's small cooler.