TH700R4 Tailshaft from 2wd to 4wd?

jorgek5:
Is the 4L60E ever a suitable option if you need heavy duty trans?

There is nothing inherently wrong with a 4L60. Where it gets a bad rap is from users/owner of them that lift trucks and run big tires and do not regear axle. This forces tranny to ride converter stall a lot and slow bakes it to failure. Then they blame tranny when it was the owner that set it up to fail. If you use the following simple formula and taking tire size and dividing it by about 7.2 you will get axle ratio you need to run if you want tranny to live. Example, 35 / 7.2 is 4.86 so you would use a 4.88. 33 / 7.2 is 4.58 so use a 4.56. Many think a 4.10 is perfect but it is not with a OD tranny. If you plan to play hard go even one step deeper than suggested (ie a 4.88 instead of a 4.56 or a 5.13 instead of a 4.88). Do not let number scare you because even a 5.13's with 35 and a 4L60's 30% OD cruises at a little over 2200 RPM at 65 which is pretty tame. Forget any illusion you have of lifting truck and cruising at 1700 RPM and getting good MPG. It will not happen and it will be a big slug and tranny will fail over time. One more important tip. Shift kits are greatly over rated and actually increase strain on tranny not reduce it. (shifts are modulated for a reason) Install a shift kit to bang the shift and you will tear the tear the splines of planetary drum hub or destroy sprags over time. Live shifts stock and they will last a lot time otherwise. Bottom line is you gear a truck with OD differently than you do with a non OD tranny but many have not figured that out and are stuck in the taller gear ratio mode.  

For me the 4L60E/TH700R4 Trans has been a great unit, when properly built and used. Being that I use my Blazer for Highway use and some moderate offroad use,the overdrive is a must. As you can see my Wheel and Tires are not even that big due to that fact that I must have a multi use vehicale that can fit many different criteria.
  According to my Tranny guy, The 700R4 and the 4L60E counter part are great units when built properly and used within ther design tolerances. You dont expect a 1/2 ton 12bolt to hold up to 37in tires in a rock crawler right? Just like you wont have a 700R4 in a tow rig pulling 12,000lbs? My point exactly.
  When deciding on drivetrain components, you must ask yourself what are you going to use the vehicle for and how are you going to be driving that vehicle. Hope this info helps   Take care and check back soon.  

I have a 1996 GMC K1500, 8" ORU Lift, Dana 44 front (upgraded axels and brakes), 14 bolt corporate rear (locked) w/4:10s, 35" BFG tirs, AEM Brute force intake, headers, true duals with cat-delete, throttle body spacer, High flow Mass Airflow sensor, and all the 4L60E transmission has done to it is a B&M shift improver kit.  I bought the truck with 84000 miles on it stock, did all the work to it and the truck has 144,000 miles on it now.  I have been doing truck pulls with it since I owned it, it is no stranger to the mud and the woods, I have pull offs with other trucks often, (mostly fords) and have never never ever had a tranny problem.  I let my girlfriend drive it one day and a tranny line let go and she drove the truck until it revved out (then she finally stops and sees the white smoke!!!), I towed it home, replaced the lines, added several quarts of B&M trick shift synthetic, and everything is fine (this was two years ago. the truck has been in 3 truck pulls since, and gets beat in the woods).  I do regular maintenance on my truck. No more then 3000 miles per oil change, tranny fluid change after every truck pull and full filter/ fluid change at least once a year.  Oh, did I mention that the truck pulls a 6000 lb farmall to tractor pulls with 2500 lbs in weights?  So tell me the 4L60E sucks.