Transmission Rebuild time

[blazerbrad]

The TH700r4 in my Blazer might finally be going out...it's a '90 with about 115k and has been used and abused for years. Never had a bit of trouble with it on the trail but it sat at my parent's place for a year and I think it got driven around the farm fields low on fluid because of a leak. Found it low on fluid and forward gears seem fine now but slips and then "catches" in reverse.

Thought about staying with the 700r4 (worked well for years), or swapping to a TH400 or TH350. Definitely stay with an automatic, and would consider a full manual reverse valve body. Would also like to stay with the NP241 transfer case because of the 2.72:1 low range....yeah, NP205's are bulletproof but have a poor 1.96:1 low range.


Here are the different options I have thought about:

1. Rebuild the 700r4
- bolt in a go, no transfer case or driveshaft mods needed
- retains the low 3.06 first gear (TH400 or TH350 are only about 2.50) = 34:1 crawl ratio
- the overdrive gear is a moot point because of how this truck is used and the axle gears
- most expensive trans to rebuild out of the other options
2. Swap to TH400
- probably cheaper to rebuild, but would have to buy the trans to start with
- super strong
- lose quite a bit of crawl ratio, and sucks up more power = only 28:1
- requires replacing transfer case, or installing new input shaft on existing transfer case
- might require modifying driveshafts to fit
3. Swap to TH350
- probably cheaper to rebuild, but would have to buy the trans to start with
- increase in strength is questionable
- lose quite a bit of crawl ratio
- believe I could get factory parts to mate up to transfer case
- might require driveshaft mods

Let me hear your thoughts and suggestions. If I stay with the 700r4 would be looking for somebody to rebuild it or help me to the work. Any suggestions on this?

If money wasn't an issue would love to have a TH400 with some sort of Doubler or Atlas, but pretty sure the wife would not be very happy with that.....