good gears for mountain driving

Can ID the rears of my hay wagon from the vin # ? rather not jack it up and spin it. Want to change for fuel mileage...

 

If it is original rear end a dealer should be able to tell you what gears are in it if you give them the vin #

 

I drive a C-13 at 470 hp, 24.5 rubber, 3.90 rears with real Jacob's brakes that will hold 75,000 gross on a 6% grade in 7-direct on a RTLO129A (13-speed with .73 final drive). Climbs like a beast as well.

I just ran a 475hp C-15 this past week that couldn't even climb small hills (3-4%) in 7-direct at 65,000 lbs (something was definitely wrong under the hood).

The motor needs to be working well and in good shape for the equipment it's attached to to mean anything. To climb any sort of mountain, you are going to want 450 hp minimum, 500-550 is better, especially if you want to gross over 80,000 lbs. 3.55-4.11 rears will be best.

 

Old school theory, 1 gear lower going down the mountain than coming up, that was the general idea anyway 35yrs ago. My opinion, you can go down a mountain a thousand times to slow but only once to fast.....
J-J

 

Good advice here. I drive a tanker so I'm either empty or #### near 80k. Most of the time 6th or 7th will do the trick on my eaton 10. Guys will fly by you thinking they are so cool buto let um. It only takes one time...

 

Still works today.

Also, if one doesn't know what gear it'll take to climb it, start in the first hole with the Jakes maxed out and keep up shifting till she doesn't gain nor lose speed and ride her down.

 

Mack E-7 350 with a "tune" (Blixxton tuner module specific for the E7 350 and injectors from the 427) no idea hp, the old man hasn't got it on a dyno yet. It can't stay with the big cats but it out pulls the company trucks with 505 mp8 m/drive. The old bull dog has 22.5lp 3.91 rears 14613 rtoo I guess you would call it the old school dbl od .62 in the big hole

65mph is 1375 with and 7.1mpg ifta

Edit: its from the 70s vintage you don't split the gears the same way you do on the newer 13/18s. Threw me for a loop 1st time I drove it. Even worse I was used to the funky up against the dash 9 pattern from the Rockwell that came out of it

 

Tell me more about those real Jacobs brakes?

 

I know what you mean, I see them going by me off Lookout Pass into Idaho like that all the time. I also smell all those brakes getting hot halfway down too. They sure don't get it do they, I run smoker loads most of the time like you do , loaded one way empty back and with my 18spd it is about the same gears maybe pickup a split once in awhile. It is nice to get to the bottom and know my brakes are nice and cool if I need them....
J-J

 

With all the different types of gearing the down and out rule I follow is 35mph down @80,000lbs and 25mph with more. If you start out using this you'll get an idea on what to do. Most important is to make sure your brakes are all adjusted and in good working order. NEVER let anyone push you or get you out of your game. Stay cool and you should be doing this as long as you like.