With the price of gas lately I have been toying with the idea of putting a overdrive in my Suburban, its our main work vehicle.

I know years ago you could buy them separately and install them in the drive shaft. Something like the transfer case in a 4X4.

But on a search I don’t find anything.

Any one got one or know anything about them?

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technology is great when it works
and one big pain in the ass when it doesn't.
Detroit iron rules all the rest are just toys.

http://www.gearvendors.com/index.html

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1986 SE 350 V8

Before you order anything... make sure you have someplace that can make custom driveshafts. You'll likely need one.

There are units that bolt to the trans much like a tranfer case.
I don't know if anyone makes a 2 speed axle for vehicles that size.

Your other option, and maybe cheaper, is see if there is an OD trans you can put in. Tho if it has an electronic trans that isn't allot of fun either.

If you do have an electronic trans... that can complicate the use of bolt on or axle od units as well. The PCM can get confused by the extra gears and trip error codes because it thinks the trans or the TC clutch is slipping. Some manual tans vehicles can react the same way now. It depends what year the truck is so make sure that any unit you look at has an answer for such an issue.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

94 GMC Suburban 4 speed overdrive automatic

From what the gervendors site says they have that all worked out but at the price I think I will just have to bite the bullet and pay $3.00 a gallon at my current mileage.

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technology is great when it works
and one big pain in the ass when it doesn't.
Detroit iron rules all the rest are just toys.