700R4 2WD vs. 4WD

[68vert]

Hello,

I have a '75 Blazer with a 3 on the tree, and I'm looking to change it to an automatic. I have a bead on a cheap 700R4 out of a '91 GMC 2WD. What needs to be done to put this in my Blazer?

Can I basically remove the 2WD tailshaft, install a different output shaft, and bolt it to my transfer case?

Thanks in advance for any help or advice.

Brian

[rs72z]

Originally Posted by 68vert

Hello,

I have a '75 Blazer with a 3 on the tree, and I'm looking to change it to an automatic. I have a bead on a cheap 700R4 out of a '91 GMC 2WD. What needs to be done to put this in my Blazer?

Can I basically remove the 2WD tailshaft, install a different output shaft, and bolt it to my transfer case?

Thanks in advance for any help or advice.

Brian

Nope. You have to tear the trans all the way down and replace the output shaft.

[babyJay]

I would avoid it. 700 are not up to the abuse of 4WD.

[86 K-10]

Originally Posted by rs72z

Nope. You have to tear the trans all the way down and replace the output shaft.

what he said...now go here ->http://www.transmissioncenter.net/700r4.htm

[Dalaigh]

Originally Posted by babyJay

I would avoid it. 700 are not up to the abuse of 4WD.

They handle it fine, both my buddy and myself have 700's in our 4x4's. My buddy runs his truck off road all the time and it never gives him any trouble. My current project has a 700 I plan to rebuild (still works, just rebuilding the whole truck cause it has 340,000kms) and run. I've run 700's in some of my older trucks and never had problems, and one of them was a truck I would run in the mud. Biggest thing is when really working the 700 keep it out of overdrive. I've towed with 700's and never had a problem, same thing keep in in drive and out of overdrive and it's fine. Helps to beef up the coolers and if you rebuild beef up the internals while your at it.

[kylep]

Originally Posted by babyJay

I would avoid it. 700 are not up to the abuse of 4WD.

i dont know nothing about these transmissions. are 700s really that bad in a 4x4? i have heard that that the 400 is bulletproof, its what i have. and i bought my rig just for going off road

[Maxxd07]

Originally Posted by Dalaigh

They handle it fine, both my buddy and myself have 700's in our 4x4's. My buddy runs his truck off road all the time and it never gives him any trouble. My current project has a 700 I plan to rebuild (still works, just rebuilding the whole truck cause it has 340,000kms) and run. I've run 700's in some of my older trucks and never had problems, and one of them was a truck I would run in the mud. Biggest thing is when really working the 700 keep it out of overdrive. I've towed with 700's and never had a problem, same thing keep in in drive and out of overdrive and it's fine. Helps to beef up the coolers and if you rebuild beef up the internals while your at it.

X2, Tranny temp gauge is your friend with a 700. I found out the hard way but I built mine after I toasted it and its survived some severe abuse in a 2wd with a mild small block and I swapped shafts and it gets abused in a 4wd now. Not a mudder 4wd but it gets worked pretty good.

[Dalaigh]

Originally Posted by kylep

i dont know nothing about these transmissions. are 700s really that bad in a 4x4? i have heard that that the 400 is bulletproof, its what i have. and i bought my rig just for going off road

If you are going to off road your truck and don't plan to drive it at highway speeds much or care about fuel economy the th400 is your best bet. It is a strong transmission, and being most off roading is done at low speeds you don't need the overdrive. The th400 is the better transmission for work, but the 700r4 has the fuel economy on it's side, which is why I use it. My trucks see a good mix of on and off road and highway driving. Another option is the 4l80e, but you'd need a controller for it as it's electronically controlled. It's basically a 4 speed th400.

[mattpiotr]

TURBO 400 ALL DAY! i had a old Chevy with the 700r4 in my opinion its a garbage transmission but opinions vary, i have never blew a turbo 400 transmission their pretty much the same as the 4L80E witch is the transmissions put in todays 2500s, But thats just my opinions

[86 K-10]

with enough cash you can get a 700 to do anything you want, all while retaining OD. even a mildly built 700 can handle 400+ hp with the proper axle gearing.

If OD isnt an issue for you, then maybe a hydromatic is the better option...

IMO most of the bad stories you hear about are from guys doing horrid things to an original 700 with a 7-vane pump.

[andrewmp6]

I have broke a turbo 400 but it was my fault i had a bone stock trans on a blown big block lol.A 700r4 stock is hit or miss if you spend the cash to beef one up it will take a beating tho.A friend of mine has a tj jeep with a beefed up 700r4 behide a 4bt cummins and its held up to that diesel for 3 years and he drives it hard.

[BigBlocksRule]

Originally Posted by rs72z

Nope. You have to tear the trans all the way down and replace the output shaft.

No, you don't. That's one nice thing about the 700R4 and 4L60E - you can swap the rear shaft and tailhousing and make it a 4WD unit without a complete tear down.

That said, I wouldn't run a 700 on anything that made a lot of torque or was used for hauling or towing.
There are quite a few vendors now selling stand-alone computers for the 4L80E. It'll take anything you can dish out and more.

[rs72z]

Originally Posted by BigBlocksRule

No, you don't. That's one nice thing about the 700R4 and 4L60E - you can swap the rear shaft and tailhousing and make it a 4WD unit without a complete tear down.

That said, I wouldn't run a 700 on anything that made a lot of torque or was used for hauling or towing.
There are quite a few vendors now selling stand-alone computers for the 4L80E. It'll take anything you can dish out and more.

Yea, the only thing you dont have to pull out is the low/reverse clutches.

[INSIDIOUS '86]

The fact that when your offloading your driving at low speeds which doesn't pull enough air over the trans cooler. So to make a 700 live with rough off roading you need to kill the heat. You can try an get a non lockup converter that will kill a lot of heat plus an oversize cooler and deep pan. Next a transform shift kit will kill shift overlap which also kills heat. Take the 7 vane pump out and put in a new one with more vanes. At low speed the line pressure rise is greater and will keep the clutches firm. If you add a boost valve and high pressure spring it will help things hold.

Most that say 700s are trash for anything are like people with fords at the track. They take a mid mile engine and add big heads and a cam with some nos and wonder why the blow the bottom end out on the track. Build your trans and your engine for the purpose. Not expect one to be fine while you do everything else
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[68vert]

Thank you so much for all of the input.