85 Sierra 700r4 Electrical Question?

[Tweeter400]

I have an 85 Sierra 1500 with the 700r4 and need some insight. I don't know alot about trannys so any help is appreciated. My question is that the previous owner swapped the motor with a new 350. When they did, my tranny shop told me they didn't hook up the electrical connections, and it is going to burn the tranny up faster than normal? With the truck having a carb on the stock engine, what are the electrical connections for? Since it didn't have an ecm and the 700r4 was the original tranny, what were the hooked to from the factory? Is this all true, or is it shady? I don't understand why the tranny shop can't hook it back like stock? In my studies of this tranny, I have found that in 85 the tranny could be hooked up without the lockout working and the tranny would be fine?

 

As you can tell I am a novice to this stuff, so any and all info is much appreciated!!

 

Thanks!

 

[heavy4x4]

The lockup you speak about in the 700R4 is crucial to keep the tranny running cool. Once you reach steady operating speed in 3rd or 4th, the computer will tell the torque converter clutch to lock. This makes the input to output ratio of the torque converter 1:1. The converter clutch will unlock in several conditions - speed decreases a sufficient amount such that your transmission shifts down to second, sudden acceleration (causing a downshift or not), and application of the brake.

 

In the '85, the signal to control the lockup was a combination of engine vacuum and the brake switch. There is also a 2-wire connector on the tranny that senses engine temperature. The system worked well and should already be in your '85.

 

Once the TBI trucks came out ('87), the ECM controlled this lockup function via the 4-prong connector on the top of the driver's side of the tranny.

 

You have two choices. Running without lockup is not one, in my mind (700's die from heat!). First choice: setup the factory system with the vacuum switch. Second choice: go to summitracing.com (or other supplier of your choice) and look for a TCI switch that gives you complete control over lockup. Personally, I would use the factory setup. You DON'T want to shift with the TCC locked - it will be a very harsh shift. With the second option, you'll need to remember to flip your switch any time you think accelerating in OD will downshift to 3rd.

 

If you have more questions, just ask me...otherwise, there is A LOT of information out there about 700R4s...check out some of the following links and also do some Google searching of your own.

 

http://purplesagetradingpost.com/sumner/te...fo/700R4p1.html

http://www.smokemup.com/tech/700r4.php

http://www.technicalevolution.com/700r4.htm

http://www.tvmadeez.com/article/index.html

http://www.tciauto.com/tci.htm

[zippy]

he's correct, that should be for the TCC. you could go through the work to get the stock system working again, but it may cost you more than it's worth. running without the TCC working right will heat the trans heavily, especially if you load the truck up much and you're losing fuel economy because of it. i'd recomend either the B&M unit, or the Superior Products unit to fix the problem.