The Stovebolt Site Forums The Shop Area Engine Shop 292 to 700R4

Any advice out there for considering putting 1991 700R4 behind a 1968 GMC 292 six cylinder.
I have only heard that there may have to be a switch to lock up torque converter?Thanks

easy to do and a real wise choice!

Good swap. The biggest problem is getting the throttle cable hooked up correctly. It must be right. There are several ways to do the lockup or you can run without it.

I have been told you cannot run without the lockup because your trans will overheat. bowtie overdrive has a very simple kit for about a $100. I havn't got my lockup kit yet but I will be soon and I will let you know how it works. The 700 made a world of difference on my 61 and I havn't even gotten it into 4th gear yet because I dont't have the lockup kit yet.

http://www.novak-adapt.com/knowledge/th700r4.htm
Easy swap, I have just put a th700r4 behind my 250ci. A real bolt-on. Make sure you do not get a 4l60e, managed by a computer; the 4l60 (no "e" is OK.
You have to use a converter lock-up switch, I have used the kit from Bowtie Overdrive: it requires removing the trans pan to change 2 cables inside, very easy, very good instructions.
http://700r4.com/tech/tcc/index.shtml

The TV (=throttle valve) cable is the other very important part, not adjusted properly, the trans will die in a few minutes. Either you use an aftermarket cable
http://www.makcotransmissionparts.com/4L60-700R4mis.html
http://www.transmissioncenter.com/Buy_Lokar_Throttle_Valve_Cables_and_Brackets_from_PATC.htm
http://www.compperformancegroupstor...mp;Store_Code=TC&Product_Code=376800
http://www.tvmadeez.com/
or you can look for an OEM piece. The problem with the OEM piece is that the cable for an inline engine is longer than the traditional small block cable, and harder to find. I went to a trans shop and they had a new one on the floor which happened to be the right length but they could not tell me what it was for! I had heard that some 3/4 or 1-ton trucks from the late '80s had a 292ci with a th70r4 from the factory... I went OEM because I prefer the black simple looks of factory stuff.
With the TV cable, you also need the proper bracket at the carb:
if you go aftermarket, the same place can sell you the correct bracket; if you go OEM, head out to the junk yard and take a bracket off any engine with a th700r4. Make sure you measure exactly where to mount the bracket on your engine, dimension between bracket and carb shafts, how high compared to the carb shaft... I made a plate that went betwwen the carb and intake, on which I mounted a junk-yard bracket (which can also hold/guide the throttle cable).
Setting the TV cable is essential but extremely easy! For OEM, any shop manual for a car with a th700r4 explain it in 3 lines.
The th700r4 does not need any vaccuum line.
Depending on the year of the trans, they came with mechanical or electric speedo drive. The best (i.e. stronger) years for this trans have electrical speedo, so back to the junk yard to get a tailshaft housing with a mecahnical gear to connect your speedo cable. Very easy again, get a tailshaft housing sealing kit (Gasket and O-rings) and while the tailshaft housing is out, you may have to swap speedo gears so your speedometer is correct:
http://www.transmissioncenter.net/speedometer_calibration_______va.htm
http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

That is all I can think of for now!

There are actually four modes of operation- - - - -depending on whether the trans is in 3rd. or 4th. gear, and converter locked or unlocked. 3rd. is direct drive, same as on a Turbo 350 or 400, for instance. The torque converter clutch can be locked or unlocked here, depending on intake manifold vacuum and road speed. 4th. gear is overdrive, and again, the converter lockup can be engaged or disengaged.

Getting the converter locked in- - - -it's best to go with OEM parts, a firewall-mounted vacuum switch, and a pressure switch in the valve body that completes the electrical circuit to the converter clutch relay. There's also a brake pedal switch that drops the converter out of lockup when the brake is applied. Early 700's had a bad habit of keeping the converter clutch applied as the vehicle came to a stop, stalling the engine just like failing to disengage a manual clutch would cause. The normally-closed brake switch was added to positively drop the apply voltage off the lockup solenoid during a stop. Throttle pressure adjustments are critical, but the lockup system can be used or not, without damage to the transmission. It does result in slightly lower engine RPM anytime it's engaged by eliminating the built-in slip in the torque converter.
Jerry