Opinions on specs for 7-13 axle setups - your dream HH truck

I have a ISX 15 600/1850 w Allison 4700RDS and 4.10 rears. At 70mph I'm at 1450 RPM in 7th gear.

As soon as it drops past 67 it will drop to 6th and keep the RPM way up. Sometimes I have to knock the shifter over to manual because it will get stuck searching between 6 and 7. Really strong headwinds tend to make it happen more. It does ok on the top end but pulling hills tends to stay at 50mph in 4th.

I've had up to 110k gross so far with it and it did alright. The biggest problem I ran into was getting started going up a pretty steep ramp in Tuscaloosa, AL. Had to lock it to 2nd. Once back on the highway it handled it fine.

 

I'm limited at a solid 105 km/h but lately I've just been cruising at 100. For the most part I hate cruising on a limiter.

I think it does OK.

 

Some of those hills are brutal, I don't run 17 between SSM and Nipigon if I don't have to. I'm also running tall 24.5 rubber.

 

There must be a few hidey holes on 11? I've never been that way. I'm in Nipigon now getting fuel ready to head out

 

We're taking this thread sideways now. I'm not sure about hidey holes but there are more places you can stop along 11, and it's nice and flat. Easy running.

 

A thread in the flatbed section going sideways? That's never happened before.

 

Cummins recommends 1650 for HH work. Keeps air flow, water flow and oil flow up.

 

Tall rubber usually has a higher weight rating. So you'll find a lot of guys running tall tires because of that. There is a little more ground clearance too. Not much, but some

 

Thanks.

What about a 13 double over?

 

I ran one for years! It did great, I decided to go with the 18 mainly just so I could split the bottom on take off. But for the most part the 13 is a great trans.