Originally Posted by Graymist (Post 452293)

Is it possible to change the gear ratios on a truck, say for eg., from a 3.36 or 3.55 to a 3.90 or 4.10 ? How much would it approximately cost, and what other modifications would have to be made ? Thanks in advance.

Originally Posted by matcat (Post 452298)

Why change from a 3.36? Unless you pull a lot of mountains it is a great ratio on an 18 speed.

Originally Posted by Graymist (Post 452293)

Is it possible to change the gear ratios on a truck, say for eg., from a 3.36 or 3.55 to a 3.90 or 4.10 ? How much would it approximately cost, and what other modifications would have to be made ? Thanks in advance.

Originally Posted by Maniac (Post 452396)

Front rear over the counter $1800, rear rear around $1300, plus labor, probably be $5000 all told, is it worth it.............?

Not to me.

Originally Posted by tracer (Post 452415)

A gear shop in Milton, ON will do it for Cnd$2,500 cash (I asked and they looked at my truck).

Originally Posted by Maniac (Post 452482)

Does that include removing and replacing the carriers? if not figure on at least 20 hours labor for both, thats in and out.

And don't forget synthetic oil at $125.00 or so for a 5 gallon pail, you will need around 7 gallons for both rears.

What kind of warranty did they give you? an over the counter rebuild ALWAYS has a 1 year unlimited mileage warranty.

All that for maybe 1 tenth of an MPG increase................not worth it, don't forget to add in 3 days downtime.

Originally Posted by tracer (Post 452315)

You're about to make a big mistake. If I were you I'd be changing gear ratios for FASTER ones, not slower ones. I have 3.73 in my 2004 International and put low profile tires and .. man ... even if I do 60 miles per hour my RPM is already at 1,375 (which is high for CAT). So I found a gear shop that can change my axle ratio to 3.58 or 3.42. They are in Canada, near Toronto, ON and the guy charges $2,000 cash plus you have to pay someone to take the diffs out and put them back in (4-5 hours of labour). If I have 3.42, I'd be able to do 62 MPH at 1,300, which is perfect.

Here's the formula to determine your road speed depending on axle ratio (AR), tires (REVs), and top gear ratio (TRAN).

RPM at 60MPH = AR x REVs x TRAN

To find out your rpm at a different speed, take the result from the formula above, divide by 60 and multiply by the new road speed. eg. 1,375 rpm at 60 mph means you'd be doing 1375 /60 x 62 = 1,420 rpm. So, at 62 MPG the engine will spin at 1,425 RPM.