In the interest of fuel milage has anyone done a ring and pinion swap in a commercial truck? I have done several in pick-ups. How much difference is there besides having 2 rear-ends to change? Would it be better to swap the whole rear-end from a cut-off?

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Ignorance scares me, Even in myself.
The only dumb queston is the one you failed to ask.
Just becasue its "legal" doesn't mean it's safe! I know when I need to sleep and when I am safe to drive. Fight the HOS. Write your Congressman.

There is no such thing as a "BACK-HAUL" everything has a start and stop point, If it needs to be moved then it is a load, period. Insurance, tires, fuel,etc... aren't any cheaper heading towards your home than they are going away. BACKHAUL is BS.

they are easy to change, just not cheap. they are basically like a ford 9 inch where the whole assembly bolts in. You can buy a remaned unit which comes assembled. you just pull out the axles shafts and replace the center chunk, put nee bearings as needed, new seals and button it up.
I think a remaned member runs in the $1500 area.

Like the other poster said its really like a 9 inch ford and you don't even have to pull the wheels just slide the axles out and swap away. The big thing is the cost versus savings. How long you plan on keeping it and how far you raise it up depends on where you start and the rest of the drive train. You need to stay in the sweet spot of what ever combo you have and still leave some to pull a hill if your running in the areas that you will be pulling long grades and stuff and carrying heavy loads you need to consider how much pulling power you will loose in the mountains. I have a friend that pulls nothing put empty trailers most of the time. He set his truck up with like 2.95 or something rears so he was turning like 11 or 1200 at 70 or 75 miles an hour got some where around 8 miles to the gallon most of the time. Then if he did hook a heavy load he just stayed in 1 gear from the top if he had a head wind or a hill to pull only time he get in the big hole was when he was on flat ground with a loaded trailer but M/T like he normally ran he was saving tons and this was 3 or 4 years ago he did that so he saved enough to off set it had he had to pay extra for it but he made the dealer do it to sell the truck. Just have to do the cost analysis's on it. How much it will change and how long it will take you to recoup the cost.

Hey Medicine Man. If you've done a front rear end, how does the through shaft to the rear rear come apart and how fun is it to line up?

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I'm a man..........And I can change..........If I have to..........I guess.

I've never done one. Only time I ever had one go out was on the road and I had it done in the shop in Finley OH