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I am just starting a total rebuild on a 56 chevy 3100 series truck. OE 235 6 cyl and OE 3 spd trans, 390 or 411 rear not sure which yet 235/75/15 tires.

I would like to have hwy use at reasonable rpm's There is a 338 rear kit in the resto catalog.

I know there was a OE overdrive on some in this era. I had one But it was lost in a divorce . But I kept the truck

If the 338 was installed would the engine actually pull it with an overdrive? If so any ideals on where to find one that works? I know about the T10 4 spd conversion, but I want to keep the column shift.

Thanks

Brad

I like the old Borg Warner over drives with 4.11 for a 6. Lock it into direct around town and let it shift into overdrive on the highway. With the .73 overdrive, you can go as fast as your 6 will break the wind. Over drive was never popular with GM, but it was almost standard on Ford. Many of the parts are interchangeable in the Ford and Chev transmissions.

And they are as rare as a queer tomcat. If you find one, see if it has a sister as I'm still looking for an O/D set up to run in my 64'.

Just my $.o2, keep the 3.90s and get an overdrive. They're not too hard to find, and fairly aeasy to work on, too. Parts can be an issue, especially electrics. But as noted, the overdrive unit itself is pretty much the same, regardless of what trans is in front of it. One suggestion I would make when looking for one, though, is don't look for one out of a truck, look for one out of a car. The reason is the car version (virtually identical other than serial numbers) is much more common. Expect to pay somewhare around $100-$150 for one. You may have to use the levers/side cover from the original trans to make it work.

I have a 59 1/2 ton longbed with the overdrive and the 3.38 gears. I would reccommend keeping the 3.90s. The truck seems to lug with the 3.38 gears and overdrive.

I see GM BW OD's on ebay occasionally. The soloniod, governer, etc. is the same as Ford or any other. I recently bought a NOS solenoid for 40 bucks that was advertised for a Rambler. Had it been advertised for a TBird, it would have brought 200. Don't go any faster than 3.90 with the rear or your od will be useless.

If you find an OD trans make sure it is as complete as possible.
Yes, some of the components from other MFG's will fit but there are some differences. The solenoids from the later Saganaw/BW OD's have a smaller diameter opening where it mounts to the unit. You can get a Ford, Rambler, or other's govenor but the drive gear will be different. Many of the internal components are the same such as the planetary set and the roller clutch but you cannot take the OD housing from another MFG and bolt it onto a Chevy trans.
Fred

I have collected about 4 or 5 od transmissions over the years, I am putting one in my '54 GMC now. It makes the greatest combination ever in these trucks. I am trying to locate the kit to replace the solenoid with a manually operated plunger. I have seen one somewhere but can't remember where. If anyone knows, I'd appreciate a heads up. My problem is I don't have a 6 volt solenoid, and my truck still has 6 volt electrical system so the 12 volt solenoid won't engage. My last one was a 1954 Chevrolet pickup (12 volt system) and it was great to drive, would cruise comfortably at 75 mph, far different than the original 3 speed.

I have on or two of them and a ford as well I think. I would like to let them go as they are collecting dust...if anyone is interested let me know.

Hans

I am running a 261 (bored .030) with a GM 89mm tranny, which has a .73 overdrive. The rear end is a Ford 9" with 3.50 gears. With p225/75R15s I run about 68 mph @ 2000 rpm. I got 20 mpg running an errand to North Platte and back. I really like this combination so far. I put a clutch assembly from a 1.5 ton truck in so if I would need to tow anything the clutch would take it.

Racecarl,

Is the 1.5T clutch a direct bolt-up to the standard 1/2T flywheel? If not what needs to change? If my memory is still accurate I think I have a 12 or 13" disc and "heavy duty" pressure plate, but they are at least 10 12-15 years old.
Brad

I am not entirely sure...
But I think the bigger AD truck clutches are called 10.5" and or 11", and they take a pressure plate that is held to the flywheel with 9 bolts. This is the clutch I have in my 1 ton.

I think the 1/2 ton clutch is a smaller disc, and fewer bolts hold the pressure plate to the flywheel. Therefore to put the big truck clutch in the small truck you also need a flywheel with the proper holes for mounting the pressure plate.

Hopefully someone else has confirmation or the right answer..

Grigg

You have to use the truck flywheel, which will have the correct holes drilled for the larger pressure plate.

Grigg is correct on size and number of bolts of truck pressure plate.