700R TO 4L80E SWAP

[TMICK]

Hello fellow diesel page viewers, I writing to try to tap into some of the vast resources of knowledge on this page, so here it goes. First I have done a search of past topics and articles to try to locate a little info on the subject, only to find just enough information to ask more questions. I have a 1989 6.2L NA silverado ext. cab longbed with a 4" lift and 35" mud t/a's. 150,000 plus miles and the third 700R with "the upgrades" ie. corvette servo, kevlar clutches etc. and I still feel like it is going to fail. I have talked to a few 'trans specialist' and one in particular captured my attention by mentioning that a 700R behind a diesel engine is doomed to fail and he does not rebuild them for a diesel for that reason. He also mentioned that during that time GM did not have an overdrive unit to handle the torque capacity of the diesel and in the later years they came out with the 4L60E and the 4l80E. Now before anyone jumps on my case, this is just what I heard and would like to come to the experts and find out the truth and find out if is it feasible to do the swap (he mentioned moving the crossmember getting a transfercase adapter and electronics from one of the aftermarket manufacturers) of my 700R to the 4L80E without pulling to many of my remaining hairs out of my head. And whats involved if it is not too much trouble. Thanks in Advance

[arveetek]

First of all, the information about a 700R4 not living behind a diesel is false. I am living proof of that fact. I have a "junkyard special" 700R4 that I bought used in 1996 and put behind my 6.2L. I've used that tranny hard ever since, with over 120,000 miles pulling large loads on occasion, including three big trips with my 5th wheel, which included many miles from here to Ohio, to Florida, and most recently to Colorado. I've never had a single problem. I love the 700 because of it's mechanical nature, and the fact that it doesn't need any computer to control its functions.

Secondly, the 4L80E is, in fact, a bit stronger transmission. It's a little stouter, but a little longer in physical length, so modifications are required. You'll have to move your transfer case and crossmember back a bit, as well as modify both driveshafts. You'll also need a stand alone computer to control the transmission. You can either get a computer out of a 92-93 6.5L diesel truck (which used a similar mechanical engine with computer controlled 4L80E), or buy an aftermarket unit from a tranny manufacturer like JET.

Jim Bigley did an article several years back in which he installed a JET 4L80E tranny into an '89 4WD truck. This might be of interest to you. In fact, if you are serious about this upgrade, I would order this book before going much further so that you will have all the info you need. The article is located on page 74 of the 1999 Feature Articles and Product Previews. Jim swapped in a 4L80E in place of the factory TH400.

I just looked on the website, and it looks like the 1999 articles are no longer available. I'd contact Jim and see if he still has a reprint available.

Personally, I'd stick with the 700. It's cheaper and easier to work on, and it's fully mechanical. It is absolutely critical to adjust the TV cable, though, or you will burn up the 700 in no time. Perhaps this might be your problem.

Casey

[TMICK]

Thank you arveetek for your well timed repsonse and forethoughts. And I also think you are right in a few areas as well. The TV cable was an issue in the second trans but I feel as though we did a long tried and true 'test and tune with the TV cable to get it to the recommended setting. I am considering toying with the trans governor and I pose this question to you and all knowledgeable viewers. Question 1: from what I have read, learned and possibly retained, the TV cable controls line pressure right? And line pressure affects shift points to some degree. Wouldn't it be beneficial to have the line pressure at it's highest and you adjust shift points through the governor, ie. springs and weights. TCI makes a nice governor recalibration kit to lower or raise shift points and in my limited thinking, I would like to keep line pressure as high as possible with the TV Cable and lower my shift points with the governor. I have always wanted to ask that question? Also this forum is great and I thank everyone for dealing with my slow learning curve.

[G. Gearloose]

Originally posted by TMICK:
the TV cable controls line pressure right? And line pressure affects shift points to some degree. Wouldn't it be beneficial to have the line pressure at it's highest and you adjust shift points through the governor, ie. springs and weights. Yes,No and Yes...i suspect.

[mhagie]

I have a Bowtie 700R4 and during the tv setup I was informed of a trick on adjustment.
It was, with a pressure gauge installed in the port just above the shifter, slide tv cable back untill pressure takes a jump,then very carefully bring it forward untill the instant it drops, that will be correct adjustment.
Seems to work for me.
Merle

[Robyn]

The 700 as it came from the factory in the early days were marginal at best.
To get a real nice 700 use a "K case" 0f 88-89 vintage and do the following. Install the torque drive system that comes with a tougher input shaft
and clutch drum with reenforcing ring at the drum splines and this kit also has the HD sunshell too Install a 13 vane pump,HD front and rear sprags,9 disc 3-4 clutch, HD 2-4 band with the corvete servo and a good quality convertor along with a transgo performance dash 2-3 shift kit. I recently did one for my Humvee Replica project. The 700 built with these parts will work well. The throttle pressure is critical. Make sure that when it makes a real light throttle upshift that stomping it then will dump it back to low gear. If not you are too loose on the TV and need more. Dont underestimate the 700 it can do the job if you build it right