captain177

1989 c3500 Chevrolet
extended cab dually
454cid w/4:10/1 diff.
what dependable 5-speed transmissions are compatible with this truck...I think my 4-speed is getting tired after 245k miles and 3 clutches. I do moderate towing with this truck, typically 8k and below because I have a Kenworth T-2000 to handle heavy stuff now....but I went from 3:73's to 4:11's and would like to get rpm's down on the freeway....help please?

Jeff

David Green

I know that this question is five years old and there were no replies but I figure that there may be people who are actually looking for answers to this. There are 5 speed transmissions used in larger trucks of days gone by. I am talking about Chev/GMC 5000 to 6500 sized trucks. A lot of them were equipped with New Process 540 (or 541 or 542) five speed transmissions. There were, in the transmissions with other than a zero as the last number, overdrive top gears and close ratio gear spacings too. If I recall correctly, they were all the standard GM manual transmission bolt pattern as used on cars light duty trucks from the mid '50s onward. Some of them had the same 1 1/8" ten spline input shafts that were the same dimensions as car/light duty truck transmissions while some of them had 1 1/2" (I think, anyway) input shafts with either ten or some other spline count. Some were longer than the light duty shafts as well. I have, a few times, used one of these transmissions in one ton trucks. The one big problem that you run into is that the transmissions do not have provision for a mount on the output shaft housing. I had to make mount adaptors out of plate steel with a cutout to fit over the extension housing, the bolt pattern of the extension housing and longer bolts. This setup worked okay. The other somewhat smaller problem was that a driveshaft had to be custom made with a larger U-Joint than is commonly found on one ton and smaller trucks. Some of the transmissions do hafe the four bolt flat flange mount and different adaptors are available to use U-Joints more common to the smaller trucks.

Drods

My 89 Chevy manual Won’t move but does shift running and off? Any ideas ? I don’t think it’s slipping