How to give a 3spd Tranny an Overdrive

[Mr. Bone]

Hello,

I need recommendations on giving my 3spd '86 military issue box van w/6.2 an overdrive. My rear axle has a 4.10 ratio.

My top spd is about 60mph without really taxing the engine. I am finding myself doing a bit more hywy driving.

Any suggestions are welcome. thank you.

[DA BIG ONE]

Hello,

I need recommendations on giving my 3spd '86 military issue box van w/6.2 an overdrive. My rear axle has a 4.10 ratio.

My top spd is about 60mph without really taxing the engine. I am finding myself doing a bit more hywy driving.

Any suggestions are welcome. thank you.

I'm guessing you have a 400 auto box, larger dia. tires is cheapest, the a changeout of rear gearset to highway frendly gears, at the high end is Gear Venders under/overdrive which will give you 6 forward gears and something like a 22+-% ratio change for some more speed or economy.......However, speedo needs calibration in most cases.

Higher speeds in a box van may make it unstable w/o proper suspension upgrades, beware!

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

[Mr. Bone]

thanks for the reply. I'm pretty sure it's a T400. . .I know it's 3spd Auto. The "T" stands for turbo? Where does turbo come into this equation on a non-turbo 6.2L?

I just looked up gear vendor. $2,600 just for parts!!!! I already have big tires. As far as speed goes, I'm not trying to go faster (maybe 5mph more) I am trying not to tax the engine so much over long hauls and looking for better fuel economy.

Is there something in between tires and a gear vendor?? How about a salvaged tranny?? Thank you.

[Craig M]

A 700R4 transmission will give you the overdrive. Driveshaft would have to get modified. There are a lot of the 700R4 around so you may find a better deal than the Gear Vendors.

[moondoggie]

Good Day!

"...'86 military issue box van..." What's one of these look like? Got a pic you could post, or a link to go see one?

A newer, PROPERLY REBUILT 700R4 is an excellent choice, with cautions if towing. It's OD ratio is (I think) 0.72 - really gets the r's down nicely. Do some searching - this has come up a few times over the years, & somewhere in the last year or so someone did a real good job describing what years/cases are the best 700R4's to build from.

T? Turbo Hydra-Matic.

Blessings!

[dieseldummy]

You could also try to find a 4l80e and use at TPS and ECM from a '91+ pickup. It would be as strong as the 400 you currently have and give lower freeway RPMs. For a non turbo 6.2 the 700r4 would likely work well, but if you're going to do a swap why not do the better of the 2 choices?

[Mr. Bone]

You could also try to find a 4l80e and use at TPS and ECM from a '91+ pickup.

Is there anyway you can define these acronyms you're using to describe this tranny? what is a reasonable price for this set up? I am relatively mechanically inclined. . .do you imagine me being able to convert it myself?

thank you.

[dieseldummy]

TPS is the throttle position sensor for the injectionpump. ECM is the computer to control the trans. You'll also need the wiring harness. I don't know the cost, but any '91+ w/the 4l80e will have what you need. The diesel depot may be able to help you out too. The swap would be pretty much straight forward. Install the TPS, wiring, ecm, and trans. Then have the driveshafts redone.

[Mr. Bone]

thanks for the input. I'm doing a bit of searching around now. Found a good number of people selling gear vendors in Ebay. I'll call around to the junk yards next week. thanks again.

[moondoggie]

Good Day!

[COLOR=black]"You could also try to find a 4l80e and use at TPS and ECM from a '91+ pickup. It would be as strong as the 400 you currently have and give lower freeway RPMs. For a non turbo 6.2 the 700r4 would likely work well, but if you're going to do a swap why not do the better of the 2 choices?" Every word true, but keep in mind: a NA (naturally-aspirated (no turbo)) 6.2 won

[Colorado Kid]

An overdrive or a gearing change will make your van a little more pleasant at highway speeds, but you're in no danger of reving a 6.2 to death. The military has been running them at governed speed for years. You'll go deaf and burn a lot of fuel, but if it breaks it won't be from high RPM running.