GMC transmission question

[SuperCab]

So I've been working on my 87 Suburban to get it ready to drive this winter... It's been rather neglected, so I'm doin the body work and gonna paint it. The other big issue it has is the fact that the pump cracked in the trans...

It gets 7 mpg. So Im thinking since it needs a trans anyway, why not go with the 700r4, 4l60e, or 4l80e? ie overdrive?

should help the mileage...


I'd need a way to control the 4l60/80e if I go that route, but the truck is set up for TBI, which I'll be going back to from this holley now that I have the money again. so If I get the ecm and wiring harness from a donor rig with the trans I want it would be no problem...

the 700r4 is weak, but i have no towing in my forseeable future, so that may not be an issue, and it would bolt in with minimal work...


thoughts?

 

[dragogt]

essayist (sp) would be trans and wiring from donor..

 

[DNFXDLI]

I gots a solution for the GM problem

 

[Fellro]

Or you can set it up by pressure switch... http://www.73-87.com/7387garage/drivetrain/lockup.htm

 

[dragogt]

Or you can set it up by pressure switch... http://www.73-87.com/7387garage/drivetrain/lockup.htm

Thats cool but it wont work with a 4l60/80e..

Unless you know something I don't????

 

[SuperCab]

I gots a solution for the GM problem

Then send all diesel excursions post paid to my home address please

 

[DNFXDLI]

Then send all diesel excursions post paid to my home address please

First thing in the morning

 

[Fellro]

Why mess with a 4L when a 700 will do the same thing with less issues? Controllers can be had, but they cost a few hundred. If it isn't already an overdrive, then the 700 is the way to go. Of course, if it has a lockup 350 in it, the 700 is practically a direct fit with no issues. The 700 is all hydraulic except the lockup, which uses the same plug as a lockup 350. A 4L60 is just a full electronic version of a 700.

 

[dragogt]

But a 700 is not as strong as a 4l80e though.

700's arnt bad but there even better when built.. jmo

 

[SuperCab]

got a th400 in it now... 700 isn't quite a bolt in but almost. nothing i cant handle...

my biggest concern was that the 700r4 wouldnt hold up in a 6500lb 3/4 ton suburban...

 

[SuperCab]

And I was gonna go back to the original paint color - Bright Blue Metallic. aka chevy blue. like this one:






It's a dark blue now like so:

What do you think? Also it sits way higher now than in the picture. and I took the moldings off the doors... severe rust behind them. they will not be going back on... same for the runnung boards... going for the clean simple look...

 

[Fellro]

They put 700's in some 3/4 tons factory stock. To keep the t-case, though, you have to go 4L80. That then requires a controller.

 

[SuperCab]

I can't mate a 700r4 to my 208 TC??? I wasnt aware of that...

 

[Fellro]

Not one that was hooked up to a th400, they have different output shafts. The 400 has a larger output shaft than the 700r4 and th350.

 

[SuperCab]

the input shaft is replaceable on the 208 though right? change it to the smaller one?

 

[Fellro]

The output of the trans spline directly into the t-case, not really an input shaft. I imagine you could switch it. Be about as cost effective to find another case over tearing through it, I doubt there is much of a shortage of them.