Outer Limits 4x4 Board

If I supercharge my 1990 Maverick SWB auto with 3.9 diff ratios and run 35" tires will I still need to change the diff ratios, is it a matter of power to run 35's or is it about the crawling ratio. The reason I ask is I'm a little confused, the truck is going to be a weekend toy only not a tourer so if I want to run 35's on 3.9 diff ratios will a supercharger save me from changing the diff ratios? Or even if I buy transfercase gears can I get away with not replacing the diff ratios?

With the diff ratios, which is the cheaper way to go:

1. Buy ring and pinion from say BBM $650 each end and pay to get them installed (4.3 or 4.6 ratio) into the standard GQ diffs.

2. Buy second hand 3L GQ or GU diffs complete and swap them over, will all my new suspension parts fit the GU diffs + do you need new driveshafts?

Thanks for you help......

Ok well i ran 35's under a 4.2L Pet/Gas Manual with the 3.9:1 ratios, lost a bit of power compared to 35's but only to the point i had to go back to 4th up steep hills, and even then i was at 90/100K's on the clock if i hit them at 120K at the bottom

If u supercharge it you won't need to change ratios, most only change them to get the speedo back into calibration as well as return the car's power curve back to standard with bigger tyres, only problem is if you want to go to smaller tyres later on (road use) you are stuffed with the higher ratios as your reving the crap out of the engine to do the same speed, you may have to do like 130 on the clock to just do 110K's actual speed.

I thought only autos had the 3.9s?? and manuals had 4.11 diffs?

manuel petrol swb had 3.9 ratios as well

Nope not all Manuals are 4.11:1. Mine had 3.9:1 in a manual Maverick

The gergories manual says that they either come in 4.11:1 or 3.9:1. I think its all to do with the Gearbox u get. The later models had taller boxes, so they had 4.11:1

Thanx...we learn all the time..it explains an issue with a friend's manual mav...