Help indentifying transmissions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

FL71C10 · 06-10-2010, 10:57 AM

Anyone able to figure out if any of these transmissions have any value? I've got a 71 sb I'd like to put a better transmission in it than a three on the tree.

http://jacksonville.craigslist.org/pts/1784554835.html

Livrat · 06-10-2010, 11:28 AM

The first one pictured will bolt right in.. Its a Chevrolet/Saginaw 3 spd overdrive.. (Although it it missing the solenoid)..
I can't say it would necessarily be better than yours (It will still be a 3 on the tree) other than having an overdrive to help mileage out..

RichardJ · 06-10-2010, 02:45 PM

The late Sag 3 spd is very similar to the Sag 4 spd. The late OD unit can be put on the back of a Sag 4 spd with a few modifications. From what I have seen, the most difficult part of the conversion is the modifications to the 4 spd shifter setup to clear the OD unit. If it isn't built properly or isn't reliable, the project will fail.

Here is a description of how it is done. http://www.chevytrucks.org/tech/overdrive.htm
The link at the bottom of that page http://www.classictruckshop.com/club...5n/rebuild.htm will tell you more about the OD unit.
There are a number of guys around on the different truck forums that have built a Sag 4 spd OD. If you are interested in doing it I would check with "truckedup", (Tony) on the http://www.oldgmctrucks.com/ forum. He took a bunch of pictures when he built his. You will have to sign up, to get into the "Discussion Boards". Tony doesn't have the truck anymore, but should still have the pictures and is always helpfull.

Some people don't like the OD unit, no matter what trans it is on. Here is a wiring diagram http://www.hydratech.com/pctc/Public...s/bwwiring.pdf and they took the time to tell you how to drive with the OD tranny.

The '84 - '88 Vette used a similar trans with a Borg Warner Super T-10 and a Doug Nash OD on the back. Chevy called it a 4+3 because the computer prevented OD in 1st gear for a total of 7 spd's. The Sag 4 spd OD gives you 8 spd's.

Most people if not all, did not like the Vette 4+3 because they never took the time to learn how to drive with it properly.
It requires a very, very long learning curve before you and the computer are on the same page, but then it becomes a really fun trans.

That missing solenoid could be a problem as they are hard to locate and often bad. The seller probably knows that. I have no idea what the OD is worth, but you will be the only guy standing in the line.

raycow · 06-10-2010, 04:59 PM

Definitiely go for the Sag O/D. This is the best of the GM overdrives and they are rather scarce because they were only made from about 66 to 69.

The solenoid shouldn't be too much of a problem. This is a Borg-Warner part, not a GM part, and they will interchange on most of the units. For example, you could use a Ford or AMC solenoid, and those are more common than GM. I see that the transmission doesn't have the governor either. You can operate the O/D without it, but you will need to plug the hole so oil doesn't leak out. In any event, it couldn't hurt to ask the seller if he has it.

Ray

06-10-2010, 10:57 AM	#1
FL71C10 Registered User Join Date: Jun 2010 Location: Orlando, Florida Posts: 2,508	Help indentifying transmissions Anyone able to figure out if any of these transmissions have any value? I've got a 71 sb I'd like to put a better transmission in it than a three on the tree. http://jacksonville.craigslist.org/pts/1784554835.html

06-10-2010, 11:28 AM	#2
Livrat Member #1049 Join Date: Jun 2000 Location: Troy Montana Posts: 3,940	Re: Help indentifying transmissions The first one pictured will bolt right in.. Its a Chevrolet/Saginaw 3 spd overdrive.. (Although it it missing the solenoid).. I can't say it would necessarily be better than yours (It will still be a 3 on the tree) other than having an overdrive to help mileage out..

06-10-2010, 02:45 PM	#3
RichardJ Registered User Join Date: Apr 2010 Location: So Cal Posts: 1,420	Re: Help indentifying transmissions The late Sag 3 spd is very similar to the Sag 4 spd. The late OD unit can be put on the back of a Sag 4 spd with a few modifications. From what I have seen, the most difficult part of the conversion is the modifications to the 4 spd shifter setup to clear the OD unit. If it isn't built properly or isn't reliable, the project will fail. Here is a description of how it is done. http://www.chevytrucks.org/tech/overdrive.htm The link at the bottom of that page http://www.classictruckshop.com/club...5n/rebuild.htm will tell you more about the OD unit. There are a number of guys around on the different truck forums that have built a Sag 4 spd OD. If you are interested in doing it I would check with "truckedup", (Tony) on the http://www.oldgmctrucks.com/ forum. He took a bunch of pictures when he built his. You will have to sign up, to get into the "Discussion Boards". Tony doesn't have the truck anymore, but should still have the pictures and is always helpfull. Some people don't like the OD unit, no matter what trans it is on. Here is a wiring diagram http://www.hydratech.com/pctc/Public...s/bwwiring.pdf and they took the time to tell you how to drive with the OD tranny. The '84 - '88 Vette used a similar trans with a Borg Warner Super T-10 and a Doug Nash OD on the back. Chevy called it a 4+3 because the computer prevented OD in 1st gear for a total of 7 spd's. The Sag 4 spd OD gives you 8 spd's. Most people if not all, did not like the Vette 4+3 because they never took the time to learn how to drive with it properly. It requires a very, very long learning curve before you and the computer are on the same page, but then it becomes a really fun trans. That missing solenoid could be a problem as they are hard to locate and often bad. The seller probably knows that. I have no idea what the OD is worth, but you will be the only guy standing in the line.

06-10-2010, 04:59 PM	#4
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: Help indentifying transmissions Definitiely go for the Sag O/D. This is the best of the GM overdrives and they are rather scarce because they were only made from about 66 to 69. The solenoid shouldn't be too much of a problem. This is a Borg-Warner part, not a GM part, and they will interchange on most of the units. For example, you could use a Ford or AMC solenoid, and those are more common than GM. I see that the transmission doesn't have the governor either. You can operate the O/D without it, but you will need to plug the hole so oil doesn't leak out. In any event, it couldn't hurt to ask the seller if he has it. Ray



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