The Stovebolt Site Forums The Shop Area The HiPo Shop 700r4 rebuilding

I have a SBC hooked up to a 700r4 (1983, non computer control). I know nothing about the transmission as it was "donated" by a friend that said it worked when he put it under the bench in his shop years ago. He does not remember what it came out of or what the milage or condition was. I pulled the pan, replaced the filter, installed it with a new torque converted. The TV cable linkage is the correct one for the Holley carb. I have had it on the road for a few very short runs (still under construction, no glass, lights or paint) . I can get it to shift but only when I run the rpm up over 2500, then let off the gas. It will not shift any other way. I've tweaked the TV cable with no luck other than to stop it from shifting altogether. I plan on pulling the drive train out in the next few weeks to prep for paint early next year. I am considering having the trans rebuilt while it's out. I live near Plymouth, WI (half way between Milwaukee and Green Bay) and would like some suggestions on good trans shops that can do the rebuild and set up with out having the truck to put it in and test run it. Or someplace I can buy a good rebuild trans and use this one as a core.

The project is a 49 GMC FC101.

Tom

There is a process to adjust the "TV" cable. Google it. I do know that if the cable is not adjusted correctly, that it will cause problems inside the tranny.

x2 what Rusty said. I had mine rebuilt before I installed it (because I knew it needed it). You might want to make sure the TV cable is correctly positioned before going the rebuild route.
I saw a rebuilt 700r4 listed at one of the vendors sites last week and couldn't believe is was listed at $2500! What????

Tens of thousands of those transmissions were used behind Chevy V6 engines in S-10 pickups. I'd suggest doing a salvage yard search for a good condition low mileage core before spending much money on a trans that has obvious problems. Any good local trans rebuilder should know a few reliability upgrades he can incorporate during an overhaul.
Jerry

The TV cable adjustment is critical and can use up a new transmission in short order. There is an article by Art Carr, a noted auto trans guru, that give good info on linkage design and adjustment for any carb set up. After destroying the second gear band twice on my 37 Buick, including one Kelvar band, I decided that the $337 that TCI gets for a constant pressure valve body was cheap. Now the only thing the TV cable does is set the shift point and has no influence on band/clutch pressure. So far, so good.

One of the frustrating quirks of the early-production 700's was a tendency for the converter clutch to fail to release when the vehicle came to a stop. Nothing like getting an engine stall like what would happen with a manual transmission if the clutch pedal isn't pushed at a stoplight!
Jerry

Definitely do your research on which (early) years of 700r4's to avoid.

One good thing GM did was continually improve the 700R4/4L60. Most of the late model components will fit on the early ones. I know the early ones had problems with the pump and forward sprag assembly. I've also seen the planetary come apart on more than one.

It's been awhile since I've had one apart, but I will recommend getting a shift kit like TransGo or another comparable. They have springs, valves, etc... that solve alot of issues.

OK my experiences are with the earlier TH350's, and other (older) trannys. But we were
always able to influence the shifting by either changing the converter, and valves for
higher stall speeds, or with the modulator valve. From my perspective, it sounds like
you're pulling too much vacuum on the (modulator) valve. Maybe relocate the vacuum
line closer to the carb, or just put a clamp on it, and see if it influences the shifting.
The valve may even need replacing.

--Chris

No modulator, 700R4 shares some design with the TH350 but pressure control is not one of them. Seen many 700R4 transmission damaged due to someone adjusting the T.V cable wrong.

So, why don’t some of you,with the knowledge, give us a short tutorial on how to properly adjust the TV cable. Personally I’m right at that part of my restomod project. Your help would be appreciated by at least one member.

Read this tech tip - - - -repeatedly if necessary- - - -and follow the gentleman's instructions to the letter.

http://www.cpttransmission.com/tech_tvcable.htm

It's a better tutorial than even a few GM training center classes I've attended have accomplished. He even goes into the geometry of fabricating a bellcrank to install a 700 in situations where it didn't fit originally. The rate of movement of the cable is just as important, or maybe more so, than its specific length for various throttle positions.
Jerry

Ahh. Like I said; my experiences were with the older TH's. But thought it worth mentioning, in case it (still) applied.
Thanks for the "heads up", BC59!

--Chris

The only function of the cable on a 350 is for forced 3-2 downshifts (hence the name "kickdown cable"). TH 400's have an electric kickdown solenoid. Both of them control shift points with a vacuum modulator. Virtually all automatic transmissions have three pressures- - - -main line pressure that applies clutches, bands, etc., governor pressure that reflects vehicle speed, and throttle pressure, controlled by either a vacuum modulator or mechanically with linkage or a cable connected to the gas pedal. Governor pressure opposes throttle pressure, causing the trans to shift up or down according to speed and engine load. That was the way things worked for 50-something years, until computers, driveshaft speed sensors, throttle position sensors, and solenoid-operated shift valves got into the mix. Now shift strategies are a whole new ballgame, determined and controlled by a bunch of computer code writers! Automatic transmissions are still smarter than all drivers, and most mechanics! It's virtually impossible to get one in the "wrong" gear for very long, like happens frequently with a stick shift.
Jerry

LOL Can't argue with that. Except I'm such a "control freak" I can't be bothered to trust
an automatic to always make the right decision. So I'm more inclined to drive a stick.
I also find it easier to drive in the snow, and to get unstuck, whether it be, snow, mud, ...
if driving a stick. But I do enjoy driving an automatic when I'm feeling "lazy".

--Chris

Very interesting information.Thanks to all the contributors.

John

Jerry, thanks. I have gone through the provided link several times and think I can handle the procedure.