Allison Trans ratings

[Wizard]

Anyone know where I can go to find out the HP and Torque ratings on my MT643 transmission. Can't seem to find it on the Allison site.

[jauguston]

Call Allison tech support. Tey will tell you. They told me my previous AT 542 was 230hp max. I had a '99 ISB engine. They said if I switched to synthetic fluid and kept the fluid out to cooler temperature below 300
° I was fine to 275 hp.

Jim

[Airtool]

Wizard ! The Torque rating on the MT-643 is 660 Ft.lbs.
Load rating for the transmission is over 70,000 lbs of vehicle weight.
The horse power can be 400,but the torque can not exceed the 660 ft.lbs. That is the max. So you need to derate the engine to meet the Torque.
Nice four speed and you can not kill them if you stay within the specks.
Military uses a ton of them and so do trash trucks.

Dick.

[downard1]

The specs pages I stubled across a few years ago said max HP is 260. I have two trucks currently running MT643's and I'm getting ready to retro fit one of them with an MD3060 Which is rated at 275HP and 800 lb ft for commercial service, or 300HP and 950 lb ft for RV use. The reason being, RV's are never loaded near the max loading that trucks are and hence the added torque doesn't have the same ill effects on the tranny.

[alvinc]

Quote:

Originally Posted by downard1 The reason being, RV's are never loaded near the max loading that trucks are and hence the added torque doesn't have the same ill effects on the tranny.

Are you sure you don't have that reversed? ....Most RV's especially the Gas Class C's and A's, roll off the dealer lot within a few thousand lbs of their max weight, and on their first owner trip are overweight.

My guess for allowing a higher torque on a RV is that they will never see the mileage that a truck will see.

[downard1]

I guess I should have been more clear. Most RV's will mostly be close to their gross weight, most RV's GVW is much lower than the max GVW rating for the transmission. For example, my RV has a GVW of 25000 lbs. However, my two dump trucks have a GVW of 50000 lbs and they are both using the exact same transmission.

[Mr_D]

On the ISC's and ISL's the torque output is limited in 1st and 2nd gears so you can't hurt the trans since that's when the Allison is most vulnerable.