Posted by Brian in Oregon on Thursday, December 13, 2001 at 2:04AM :
In Reply to: Re: M-37 Owner needs some help and advice posted by Charlie on Wednesday, December 12, 2001 at 3:56PM :
John J, everything is a compromise when you start altering specs on vehicles.
IF you go a gasoline V-8 swap, you'll have to decide if 3200 rpm at 55 mph suits you, or if you have to have it go 65 mph at 3600 rpm.
Sustained 3600 rpm is quite doable for a properly prepped and balanced V-8. I drove a big block at 3500 rpm sustained daily for a 42 mile round trip. A shorter stroke would be preferable, so a 318 or 340 block and crank would be a help. You'd also want to select you cam and intake to be optimum at that rpm band for fuel mileage.
However, it isn't really the engine that's the problem. The transfer case is very loud from 45 mph on up. Some owners say they literally have to yell at their passengers at 60 mph.
An overdrive, even behind a diesel, is not going to do anything for the transfer case whine. I'm not aware of any successful overdrives that would go behind the M37 transfer case. That leaves only two ways to reduce the rpm on the transfer case. Either do a gear swap to 4.89's, or run larger tires. (Or both).
As for diesels, if wishes were fishes we'd all cast nets. The problem with diesels is the expense. Not everyone can pony up for the initial outlay, regardless of the long term benefits. The diesels I've looked into all rev out at roughly the same point as the old flathead, so a gear change or overdrive or larger tires is a must to run above 55 mph.
I'm satisfied to run at 55 mph. We only have two highways where you can run faster than that legally anyway. The 5.83 gears offroad mean more to me than more speed. But many folks are not satisfied with 55 mph, and that is quite understandable.
You need to decide what it is you expect the truck to do, and what you are willing to compromise and spend to get there.
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