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

No one has mentioned axle ratings. I knew a guy out of fla who said he had to replace his tears every year. I asked him what kind of weight? He said he'd do 130k regular down there on a 6 axle. I asked what kind of rears he said eaton's. I said no what is the rating. Well, turns out they were 40k rears. Hmmm! Think maybe there's a connection?

 

46s and I should of got 52s....

The only way to fly.

 

Same case, gears are heat treated differently to be stronger, pilot shaft Has more splines.

 

I do know for a fact that you can't just switch ring and pinion from 3:55 to 4:11 unless you change the cage ( what the ring gear bolts to) it is same cost as just changing the whole member.

 

Thank you.

 

So not really a HH question- But if you run a 13 double over, does that help compromise running a lower gear ratio? You could have 3.90s or 4.10s and still have some legs up top to run?

I'm surprised no-one mentioned tire size. Like Six said and father and son holds true for tire size. You have a truck with 3.90 gear ratio and short rubber, change the tires to tall rubber you essentially change the gear ratio to 3.73s or 3.54.

 

Thought I'd throw this out there...

My Pete has a 3.55 ratio paired with an 18-speed and a 485 Cummins (CM870 rated at 500HP), always grossing 125,000 lbs to 140,000 lbs loaded with a B-train. It runs just 1,280 rpm at 100 km/h or 62 mph.

I'm still learning but it almost sounds like that cruising RPM is lower than it should be. I read somewhere on some publication from Cummins that had stated something about rpm at cruise speed should not be less than 1,370 and that was referring to 80,000 lbs gross weight.

Of course theoretically it should yield better MPG the way it is, but is it harder on the engine?

 

Theoretically in a high hp engine. you keep rpms up to increase air flow thru the engine ....

 

The Bohemian answer is to just go faster till it hits the sweet spot.

I'm assuming your governed at 100k for Ontario? That setup sounds like it would fall on its face if it even smells a hill.

 

I'm roughly the same. 2014 Volvo D13, 455 horse, 3.55 gears. It's brutal in the hills. Northern Ontario going out 17 I was climbing hills at 20 mph. I was only 100,000 pounds. Good thing I brought a book to read.
I'm going to try 11 on the way home.