I have posted other questions on this subject before, but come next Monday the deal will be done so I am looking for any information/opinions any of you may have. I have a '01 SCAB 4.6 w/3.08 gears & 16" tires. The truck with this rear gear is only rated at 2000 lbs. according to the towing charts, but gets about 17.5 miles to the gallon. I live and work in south ms driving 25 miles to and from work a day about 15 miles rural hwy about 10 miles stop and go traffic. I am looking to get the 3.55 gears installed, which will raise the tow rating to 6900 lbs. The sole purpose for this change is that I have purchased a 23' travel trailer which weighs about 3700 lbs dry. I have pulled the trailer with the overdrive off, short distances and the truck does fine. But I would like to have the little added insurance of the lower gears to take the extra strain off the transmission. Does anyone know what I can expect from things like gas mileage for the daily commute, and the overall feel from the truck having the lower gearing. Thanks

 

I would go with at least a 3.73 myself, maybe even a 4.10. 3.08 to 3.55 is not going to yield that much difference. I have 3.73's factory on my 2wd and they are a pretty good all around gear. If you switch out them 3.08's you will feel like you picked up 50 hp, trust me. With the good tall overdrive we have these days, and the 10 miles stop and go driving you do, I think 4.10's would be nice, especially towing. There have been many people on here who have done it, maybe they will chime in.

 

To answer this question, I get 15-16 local driving and have gotten as high as 18.5 on the Highway with 3.73's. Of course mine's an '04 with a 5.4 3v. It may cost you a small amount for highway driving, but very little if any when driving stop n go. What size tires are you running?

 

Thanks for the reply. My truck is all stock with the OEM BFG 235/70/16 tires. The only add-on I have ever done to it was the k&n air filter. Thanks again.

 

This may help in gear selection. 235/70/R16 is 29" tall.

http://www.4lo.com/calc/geartable.htm

 

The truck will feel like it has a supercharger.
You will gain a little (0.5 to 1) mpg in stop and go city driving but may loose a little (0.5 @65mph 1.5 @80 mph) mpg on the highway.

Fritz