Hello folks, was wondering if anyone could answer this question for me. Have 1993 D350 with a 4:11 rear end on it and am considering changing it out for what I think is the 3:54 rear end for gas mileage purposes. Question is what kind of gas mileage improvement can I expect to see. This truck also has a governor on it I am assuming because of the 4:11 rear end, can this be disabled or will it tear up the tranny if I have that done. Any thoughts would be awesome.

Thanks Bob C

 

Welcome to DTR, Bob In a perfect world, you'll never burn a drop of 'gas' in that '93 Just funnin with 'ya 3.54's would definitely help fuel mileage. I wouldn't give much more than 3 or 4 hundred for a rear, just for reference. Yes, the engine is governed. You can't disable the governer, but it can be altered. check the 'sticky' at the top of this forum for more info. There are many small tweeks to do before you even get the governer spring, although the spring will be the best 20 bucks you ever spend on the truck

 

hey bobby i have a 93 d350 that has a 354 rearend ill trade you for urs

 

you'll be very sorry

 

Just to show the effect of that 366 spring.
I have a truck with a 518 & 3.54 gears.
The spring changed the truck from barely able to do 55 in 3rd to easily making 80 in third.
It will do wonders for top speed.

 

well i got 235 85s on it now and it dont have the towing power i want guess im to used to towing with the 2nd gen lol

 

Adam: if ur not towing on the highways you may like the 4.11 more, i think if you would like to keep your top end stay with the 3.54s you have. Doing 3500rpm you'd go from about 80mph to 70 mph, doing 65mph(speed limit around here) you'd go from you'd go from 2800rpm to about 3300rpm

 

yea thats what i figured i do a little hiway drivein but mostley towing up the mountains and thats where it kills the truck, and i only tow around 6k pounds i think a good tq would help a lot

 

Thanks for your input guys. I pack a 12ft camper that weighs close to 4000 lbs fully packed and the majority of the hauling is on the low lands with very little mountain towing. I really don't mind taking it a tad slower up the grades I pretty much do that anyway to try and keep the repair bills down lots of luck.

So the last question would be if I do change out the rear end to the 3:54 and change the governor spring, it there a possibility that i would tear up the tranny? or is that a none factor.

Thanks again for the info.