Question about the automatic transmissions

[Gearstix]

How does the 6.2 700R4 vary from the gasser version? What controls the shifting, is it a TV cable like it is with the gas version?
I'm trying to figure out how to do an automatic transmission with no computers and no vaccum do-dads.

[convert2diesel]

Internally there is not much difference. The diesel has a different govenor (effects shift points) and the apply servo is different (you will see it described elsewhere as a "Corvette servo"). The transmission is controlled by the TV cable as it is in the gasser.

The big difference is in the torque convertor. You can get by with the gasser but the tranny feels sloppy if you do. The diesel torque has a very low stall speed (1,200 to 1,400 RPMs) to make use of the low end torque of the diesel.

Controlling the lock-up is an issue. Some of the original versions used two pressure switches in the third and fourth gear circuits that were hooked up in series to ground through a throttle switch on the IP. This worked well as it only gave the TC apply solinoid a ground in third or fourth. Subsequent versions used a rudimentary ECM to apply ground to the TC solinoid at all speeds over about 40MPH, with a Hall effect TPS on the IP.

Internally, the TC only gets pressure from the second gear hydraulic circuit so that there should be no way your TC remains locked up in first or when you are stopped. To control the lock-up, you have four choices:

1. Do as I did and put a switch on the dash to manually lock-up the convertor.

2. Purchase one of the vacuum controlled kits available. This will require a vacuum source and the TPS from a THM 400 equipped 6.2.

3. Find a tranny from the early 80s with the two pressure switches in the valve body and wire it through the afore mentioned 400 TPS (unlocks the TC at high throttle settings) but you will be stuck with the reliability problems of the early 700 R4s.

4. The best way without some sophisticated electronics is to use a modern 700 and have the third gear pressure port drilled out and tapped for an additional pressure switch (all the 700 have the boss cast in for both third and fourth circuits..you will have to remove the valve body to do this). Install the pressure switches from the early version (both should have the 3 second apply delay to keep the tranny from being locked up during shifts). Wire the ground from the TC solinoid through the pressure switches in parallel but in series with the 400 TPS (ground is through the TPS). Note. This set-up has no provision to un-lock the TC at low or zero throttle. In other words, the TC will remain locked up when coasting or going down hill unless you physically shift the tranny into second gear. I would still install the switch on the dash for this reason and it would also give you the ability to un-lock the TC on heavy pulls at part throttle.

Hope this helps

Bill

[Gearstix]

Internally there is not much difference. The diesel has a different govenor (effects shift points) and the apply servo is different (you will see it described elsewhere as a "Corvette servo"). The transmission is controlled by the TV cable as it is in the gasser.

The big difference is in the torque convertor. You can get by with the gasser but the tranny feels sloppy if you do. The diesel torque has a very low stall speed (1,200 to 1,400 RPMs) to make use of the low end torque of the diesel.

Controlling the lock-up is an issue. Some of the original versions used two pressure switches in the third and fourth gear circuits that were hooked up in series to ground through a throttle switch on the IP. This worked well as it only gave the TC apply solinoid a ground in third or fourth. Subsequent versions used a rudimentary ECM to apply ground to the TC solinoid at all speeds over about 40MPH, with a Hall effect TPS on the IP.

Internally, the TC only gets pressure from the second gear hydraulic circuit so that there should be no way your TC remains locked up in first or when you are stopped. To control the lock-up, you have four choices:

1. Do as I did and put a switch on the dash to manually lock-up the convertor.

2. Purchase one of the vacuum controlled kits available. This will require a vacuum source and the TPS from a THM 400 equipped 6.2.

3. Find a tranny from the early 80s with the two pressure switches in the valve body and wire it through the afore mentioned 400 TPS (unlocks the TC at high throttle settings) but you will be stuck with the reliability problems of the early 700 R4s.

4. The best way without some sophisticated electronics is to use a modern 700 and have the third gear pressure port drilled out and tapped for an additional pressure switch (all the 700 have the boss cast in for both third and fourth circuits..you will have to remove the valve body to do this). Install the pressure switches from the early version (both should have the 3 second apply delay to keep the tranny from being locked up during shifts). Wire the ground from the TC solinoid through the pressure switches in parallel but in series with the 400 TPS (ground is through the TPS). Note. This set-up has no provision to un-lock the TC at low or zero throttle. In other words, the TC will remain locked up when coasting or going down hill unless you physically shift the tranny into second gear. I would still install the switch on the dash for this reason and it would also give you the ability to un-lock the TC on heavy pulls at part throttle.

Hope this helps

Bill

Well I've been planning on doing a diesel swap in my S10 but the transmission is the problem. I'd like to have an automatic.
I was planning on making an adapter to bolt up a GM automatic trans to a inline four diesel. I have a 4L60E right now but the only way I've found to get it to run without the computer is the Transgo 4L60E-3 reprogramming kit.

"Stick Shift; Full Manual Control; Converts back to automatic. For transplant or use with no electrical: Includes: 46-MOD (Vacuum controlled line pressure)."

Vacuum controlled line pressure... :( I've been told this would not work with a diesel.

I'm not sure how I'd adapt a TV cable to a Isuzu or Perkins say,...