I posted a message about this on O/O forum... Getting ready to rerate the CAT from 1650 torque to a higher number. A local Peterbilt dealer surprised me by saying they can help me without asking too many questions about my RTLO-16913 transmission and 1700 lb Solo clutch.

I was playing with the Horse Power/Torque formula trying to decide if maybe I should go with 1750 torque instead of 1850 (to ease the pain on the tranny and clutch). My best-pulling RPM is 1350 when the engine develops 424 HP. This works great even with 45,000 lb loads going thru hilly places. If I increase the torque to 1750, the HP at the same 1350 RPM will become 449 HP. And with 1850 torque rating, the engine will make 475 HP. Maybe I don't need 475 HP? I'm still going to be pulling dry van loads, with the maximum gross weight of 80,000 lbs.

Another question is what can I do to spare the drivetrain from overload? One mechanic I talked to said the most important thing is to start slow, but once you get going the tranny can take it. He said most danger comes from starting and getting out of snow, let's say, when you're stuck. Are there any other tips I should know to keep the drivetrain damage-free after the torque is increased?

 

Being stuck in snow is hard on any drivetrain. The spinning and momentum of the wheels and engine, and sudden traction when you spin through can do a number. If you're idling when you do that, you should not have the maximum torque on the drivetrain. If you start playing with the throttle, you will increase the torque you are applying and could tear something up. The worst thing is any kind of sudden torque against it. Like popping the clutch. The sudden stop of one wheel (or two) will do the worst damage, in my estimation.

 

Thanks for the comment, windwalker. I just got back from the first trip with an increased torque of 1850. I kept the same tranny and clutch (1650 rating). Despite what many people said on this forum, I already felt the clutch spinning at least once: I was going up a small hill in 4th gear from the ramp towards a truck stop and decided to accelerate and shift into 5th. I had 45,000 lbs in the box and as I released the clutch, the truck shuddered as if I still had my foot on the clutch. I was doing okay on a highway cruising at 60 mph ... but still, I decided to upgrade the tranny and clutch. I'm picking up my brand new 2,000 lb-ft torque LIPE clutch tomorrow The funny part is it's almost 3 times cheaper than a reman'ed Solo!