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TH700R4 Rebuild or ??

D

Dave'90K5

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I have a 700R4 in my 90 K5 with 6 inch lift, 35's, and 3.73 gears. We lost 3rd and 4th gear last weekend while wheeling. Should I keep the 700R4 and rebuild it or is there a better more suitable trans?

Edit -

OK - after reading earlier posts about what trans is best and what mods to the driveline should be made I think I have become confused!!

I'm guessing I should rebuild my 90 700R4 with a shift kit and call it good or should I replace it with a 4L80E?

What is your opinion?
 
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Personally, I'd keep the 700r4 and have it rebuilt or replaced. I'm guessing that it was the original tranny and has seen a lot of use in its lifetime and was getting weak. The 3.73s with the 35 inch tires are putting some stress on it, which probably just sped up the inevitable death.

There are some other options, like a manual transmission or one of the 3 speed autos, but I'd still keep the 700. The 4L80E is nice but its expensive. You'll need to buy the transmission and then the stand-alone computer to run it. It's also longer (I think) so you'll have drive shaft length issues and I'm not sure what the spline count is on the output shaft but I'd bet it's different, in stock form, from the 700 so you'd need to change the output shaft or change the transfer case to match. It also has a higher first gear (2.48:1 vs 3.06:1) and a lower OD (.75:1 vs .70:1) than the 700.

Regardless you may want to think about different gears in the axles whether that means re-gearing what you have or swapping axles. 4.56 gears, 35 inch tires, and an overdrive tranny is a nice combo. Lower gears will perform better all around; you'll have a better low end for off-road and just getting the ol' Blazer moving and you should be able to better utilize OD on the highway. Make sure you have a good transmission cooler, too.

Find somebody that knows how to build a 700r4 and have them puts some better parts in it and you should be good to go. If you search some you should be able to figure out what needs to be upgraded.

Good luck.

Jason
 
Jason -

Thanks so much for the helpful info... I know the subject has been hit hard throughout the Forum but it's always good to get a quick and dirty answer.

Dave
 
Ok one last question...

Do you recommend replacing the torque converter when I rebuild? Part of the reason I ask is because I drove it about 200 miles in 2nd gear to get it home. No slips or problems just a slow go at about 50 - 55 mph down the highway. The engine RPM was up there but since I don't have a tach I can only guess it was about 3700 rpm.

Thanks,

Dave
 
Anytime you rebuild a tranny it would be better to replace that converter simply because anything that let go inside the tranny could now be in the converter and there fairly cheap compared to the rebuild
 
New torque converter only cost 50 bucks at a specialty transmission shop.. i paid either 49 or 54 bucks for a stock 1700stall torque converter at Dacco Detroit http://www.daccoinc.com/ http://www.daccoperformance.com/

To rebuild my TH350.. with new torque converter, gaskets, tcase adapter gasket, vents, all for 149.95 in parts. I rebuilt it with my uncle so that was the total cost.

But for "should i" replace it.. I have no idea i dont know much about them. But i was told by my uncle to go ahead and buy a new one.
 
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