A study in logistics.

[convert2diesel]

Dr. Lee:

Or for that matter, anyone who knows their way around the 700R4/4L60.

Have made it to the tranny stage of my Buick/6.2 conversion and have run into a snag. Having discovered that the tranny I got from the donner truck (1987 6.2) had been used to pull stumps out in the field, I resorted to trying to convert the 700 from the Buick.

Will be using the torq from the truck, and the govenor. My problem seems to be how to activate the TCC. The 87 had two Pressure switches that could be easily wired to activate the solinoid but the 91 only has one.

This switch is tapped into the forth gear apply circuit and can be wired to activate the TCC in forth. The problem exists in that there seems to be no way to tell, even the old computer let alone any relays that I can design, when the tranny is in third.

Some variants of these had a 3/4 "pulse" switch, but according to the hydraulic schematic supplied by All Data, this switch is only on the forth gear circuit and the third circuit tap is welded over. This is parroted in the wiring schematic and the physical wiring in the tranny.

I do know that the TCC activates in third when using a fuel computer ( have been driving the car for the past 6 months), but according to my info and wiring schematics, this should be impossible.

Am I missing something? I do need lock-up in third, and I refuse to use any damn computer, plus would prefer not to have to use a switch on the dash.

Any ideas? Any info or imagination would be greatly appreciated as this is preventing me from completing my task, and I'm sooooo close.

Thanks in advance.

Bill

[gmctd]

Replace the switch with the 4rth switch from the 6.2 trans.

The Buick switch is not grounded - second wire comes off switch to the computer, which supplys ground when emissions-acceptable.

Or, wire in the needed ground.

Also, the Buick trans does not have as many clutch plates as the 6.2 version, so will not have stump-pulling capability.

And you will need to use the 6.2 (dk gry?) line pressure spring.

This is same spring supplied in aftermarket shift kits, and is highest pressure available.

Shifting is controlled by governor and valve body, so use 6.2 fly-weights for closest match.
Valve bodys are not interchangeable below 1988.

Servo springs are hd for the 6.2 version.

125 bucks will get you a complete rebuild kit, and is not difficult to install.

Was some difference in pump splines and number of vanes between '87 and '91, so '87 TC may be a problem.

[convert2diesel]

GMCTD:

Thanks for the input

Did some additional research after my original post and discovered that the computer activates the TCC whenever the VSS signals speed over 36 MPH (I assume GM figures that by that time you are out of 2nd gear). The 4th gear solinoid is used as a momentary disconect for the 3/4 shift and presumably 4/3 shift.

According to my information the computer needs only the following:

1. Engine heat over 110 degrees
2. VSS signal over 36 MPH
3. Steady state TPS signal over idle (>1.25 volts) or below 70% throttle angle.
4. Power through the brake switch

For now I think I will utilize the TPS from the diesel (same output as gasser), Install resister across the temp sender and leave the rest open ended except for the VSS. Hopefully the default programming for the computer will allow the TCC to function independantly. If not will have to invent dummy loads for the balance of the sensors.

You are right about the pumps and spline differences but I believe they went from 27 to 30 splines in 84 and the aux valve body in 88. As mine is a 91 that should give me the latest pump and the aux valve body, but I will have to live with the 6 clutches as opposed to 8, at least until I standardize the design of the tranny. Will have to see if the apply pressure is enough in 4th but will probably not need it as I normally tow in third. It should hold together long enough to do the initial testing (he says with unfailing hope!!!).

Thanks again for the input and will keep all posted on the results.

Bill

[convert2diesel]

gmctd:

Everything worked out as expected except that the diesel torgue convertor I had turned out to be leaking. For the present I am using the gasser torgue, gasser spring but with the diesel governor. That has got to change. Shift points are way off but the tranny will work for now as long as I can keep my foot off the floor. Will install re-built diesel set-up before I try to tow anything.

As far as the TCC is concerned, my hope that the controller would still work in default was not realized. Currently using the ALDL test port to manually activate the solinoid. I have to figure a way to correct this situation.

Perhaps with your knowledge of logic circuits you could give me a hand. In theory (famous last words) if we could get a circuit that would activate with a VSS signal over 44.5/sec (assuming 4000 cycles per mile at 40 MPH), combined with a 5 volt power supply to feed the TPS that would inturn close the circuit at aprox 1.0 volts and break the circuit again at say 3.5 volts, then we would have it.

Is this do-able, or am I pie in the skying it? Up here I can get a re-built diesel controller for this tranny for $95.00(CAN) plus $100.00 core, and the local GM dealer will sell me the EPROM for $75.00. That would at least be a plug in solution, but it wouldn't be as much fun, now that I have acquired my new found talent at electronic assembly, courtesy of your's and Dr. Lee's tachometer controller. Didn't my father say a little knowledge is a dangerous thing?

Anyway any input would be greatly appreciated.

Bill

[JeepSJ]

B&M Transmissions has an electronic lockup controller. It goes strictly by vehicle speed. The kit comes with its own VSS and the system is adjustable for the lockup RPM. Or, you can do what I'm going to do and just control the lockup manually with a switch, or as in my case a couple switches so that I can also lock 3rd when I'm towing. You may want to check out the boards over at Bowtie Overdrives (www.700r4.com). Also check out their wiring kits.

[convert2diesel]

Jeepsj:

Good advise. The B&M is the first one of this ilk that I have seen that allows lock-up in third gear. I guess the others just assume that forth is only used when coming home from the track, thus lock-up is only needed occassionally.

In my case, when pulling a load, it is preferable to do it in third, but without lock-up, you can fry eggs on the tranny cooler after only a few minutes.

Thanks again for the lead. Summit sells it for $160.00 (US). Maybe I'll wait until our dollar gets over a buck (US) and make out like a bandit.

Bill