Duramax Owners a Question

[RMccord]

I have a stock 05 GMC 2500HD Duramax/Allison. I tow a 335RLBS with a max weight of 11100. Normally it is around 95-9800.
Have any of you felt the need to increase or change the tranny cooler.
If so how much improvement in temps did you get.
SO far my temps with stock cooler have been non towing 125-160. Towing up grapevine 85-90 degree weather 175-190. Any thoughts or feedback appreciated.
There is a trans cooler I came across offered by Inglewood Transmissions made specifically for the Duramax that will reduce temps about 20-25 dgrees and is a drop in replacement. I can get further details if you wish. Switch out takes about 30 minutes and requires no cutting or fitting. I found out about it on the Diesel Place Forum. Cost $450 with all brackets and cooler, etc.
Thanks
Bob
I am trying to determine if this is worth the investment over the stock one. 20-25 degrees could be worth it.

[Bill Hill]

Bob,
as you can see by my signature, we're towing a 2980RL with a stock '04 Duramax/Allison. I recently weighed in and the trailer was at 11,500 loaded for a trip. The one thing I DON'T worry about is the transmission temp. We just got back from a long weekend in AZ from LA, pulling up Hwy 89 into Prescott in 90+ temps and the transmission temp never went above 190 F. I worry more about keeping the EGT under 1300F when pulling up a hill.

By the way, one of the prettiest RV parks we've ever been in is the Far West Resort in Santa Paula. We also live in SP, San Pedro CA.

[melnjoy]

Bob
I tow a 3575RL and have it loaded down pretty good, [have to have all my things.] I have been over all the passes here in washington and I do not spare the horses. I have been plesently suprised to find that the Tranny has never come close to getting hot.
Mel

[Montana Sky]

I tow the 3400RL with a weight of 13,400lbs and just brought the coach home from the lake on Wed. with the temps in the 98 degree mark. My truck is fully stock other than the EGT and turbo boost gauges and a custom flow tail gate I installed. I watched the tranny gauge while towing home and I do have a few good 6 - 8% grades over 3 miles to pull out of and the trans never got over the 200degree mark. Like Bill said, I have to worry more about the EGT going over the 1300 mark well before the tranny temp gets that hot. Engine temp got right to the 210 mark I think it is and the fan kicks on and cools that thing right down. Like Mel and Joy I also am in Washington and have pulled all the grades around here with no worries. In my opinion you will be more than good with the factory tranny cooler you have on the truck. Save the $450 and spend it in fuel to take another trip with your Montana.

[tweir]

Bob & Carol,
Your temps are OK. I ran just under 200 degrees (trans temp) pulling the 3685FL and engine temp around 195-205 and that was pulling a 6%+ 16 mile grade from Baker CA to Vegas with ambient air temp around 86 degrees. As mentioned, watch those EGT's. At my next O/C, I'm going to change out the Allison spin-on and see where I can send in a sample of both engine & ATF for an oil analysis.

[sreigle]

Bob, sorry to butt in on your GM thread but I wanted to express my opinion that your temperatures sound very reasonable. We run just about those identical numbers towing 14,360 pounds (22,920 gross). Sounds to me like you don't need extra cooling but that's just my opinion.

[NJ Hillbilly]

I didn't add extra cooling but I did make a few changes. I went to an Allison Trans shop (not GM dealer) and ordered the standard 1000 series transmission pan and sump pick-up. Changing from the original pan to the new one added almost an extra 3 qts of fluid. The parts added up to less than $75. I also bought a 5 gallon pail of TranSynd synthetic from them. I drained the fliud from the trans, changed the pan and filter, and overfilled the trans. I then removed the line from the trans to the cooler and started the truck, this pumped the old fluid out and I watched till the fluid cahnged color. Now 90-95% of the old fluid is out and synthetic is in. A 5 gal bucket of fluid was about $130. So for around $200 I have fluid that is supposed to be good for 100k miles under normal pick-up truck service. I will change it much sooner but the peace of mind is there.
The trans temps stay cooler longer and I know the fluid will not suffer from the heat.

I also highly reccomend finding an Allison shop to buy trans filters from, they get $7 for them, I know the dealer gets significantly more $$ for them.

As for the gauges, I recently installed the Edge/Attitude programmer. One thing I learned is the dash engine temp gauge is an idiot. It never moved any more than 195-200 deg while the Attitude's digital readout from the computer went from the low of 180 to a high of 216. That's a big swing in temp for the dash not moving much.

I would reccomend the pan and fluid change and skip the cooler.


John