Question about rear ends??
 

I found this 04 columbia, 13 speed,14.0 engine with 2.90 rears.What do you guys think about this set upfor power,fuel mileage,speed? Most of my friends haven't heard of gears this low and their views are different.Would like to hear from whom may know about this stuff.:thumbsup:

Low??

That would be high geared. Should fly across Nebraska

A guy called Rutherfords show last week, he bought one of those and hates it..he said it gets lousy mileage and runs like crap.
kevin said with ultra low pro 22.5 and 60 mph it would do okay

Okay, 60mph wont cut it for me.I need to run at least 65 to 75 and still get decent mileage.I should mention that it has a 14.0 detroit.Just talked to one of my mechanics and said it was a good set up.But i still want to hear more from others.

TY

This little formula might help you decide:

RPM at 60 MPH = Axle ratio X Tranny ratio X Tires revs

I guess this truck has a direct drive tranny, so the "Tranny ratio" (top gear) will be 1. Regular 22.5 tires do usually 495 revs/mi; while tall rubber (24.5) do 473 revs/mi. To find out the RPM at 65 or 70 you put in all the numbers in this formula and then divide the result by 60 and multiply by whatever speed you plan to run at.

Example: tires revs=495, direct drive (1 ratio), axle ratio-2.90. The engine RPM at 60 MPH will be: 2.90 X 1 X 495 = 1435. The engine RPM at 65 MPH will be: 1435 / 60 X 65 = 1555 RPM

If you play with various tire types, you can find which setup will produce the RPM that Detroit recommends for cruising on the highway.

I have 3.55's and I do 70 at 1500 rpm. 24.5 low pro. I would get higher if I ever changed them.

The faster I go the better fuel mileage I get.

With the specs you listed I'm sure it's an old Swift truck. They have 2.93 rears with a direct 13sp. That tranny and rear end is near the exact same as an overdrive 13sp and 3.55's.
That transmission was originally a RTLC-16609E, once converted it's a RTLO-16613B, Top hole is now .85

That would put you at 1400rpms at 65 and 1600rpms at about 75.

Yes.You are correct.It is a swift truck. Right now, my t 2000 with a 10 sp,3.55 rears runs me at 1500 rpm @ 65.Over 1500 at higher speeds.The problem is that it really needs a rebuild and that would cost me over 10k.And once you put money into it,It never ends.According to my numbers from last year,i had quite some big numbers on repairs.That's why i decided to go with another truck,less expensive, since the economy is the way it is.A little protection from both sides.

But yeah, if any of you guys had any experience with this type of set up dont hesitate to post.

TY

I own an old Swift truck. One of the blue ones, just like the white ones except it has power windows. I had very bad luck with it at first, but a new engine, clutch, and rear main seal later, I'm in business. I get an average of around 6.8mpg pulling intermodal through the hills of Missouri. Heavy loads, 45,000 plus

New engine??? Man that's crazy!Let me know what issues you had with that detroit engine.I only dorve a cummings and had no problems at all but im new to detroit.Also 6.8 mpg is excellent on those trucks.