700R4 slips at 35 mph

[neo]

Hi all, My 84 Jimmy has the 700R4 tranny and when I bought it the PO sold it to me with tranny issues. I found it did not have a TV cable, so I put one in and adjusted it according to the manual from Haynes on the 700R4. I did this by pulling the throttle on the IP all the way open and then pulling the TV cable all the way extended and locking them at that point. Please correct me if this is incorect. Anyway, what it is doing now is shifting rather nicely from 1->2 then 2->3 and then at about 35 mph is feels liek it shifts into neutral. THe tranny just slips away. Now if I press the accellorator a bit further, I can hear it downshift and then the tranny catches again but the engine is spinning pretty fast. Moving the lever (shift) down the D does nto seem to help. It does have (the tranny) a electrical plug on the pass side near where the TV cable goes in. I am uncertain if the TCC plug is energized (on the drivers side?) Any suggestions are greatly appreciated.

Neo

[justy330]

I don't know. Almost sounds like the TCC is not locking.

[neo]

Thanks! It has me stummped. I am going to try to chase down the TCC, I believe it is via power on the D/S four pin plug?

[Subzilla]

I'm not a tranny expert but I have had some TC fun in the past. The TC circuit runs through a throttle position sensor on the side of the IP then through a brake pedal switch. I bypassed the position sensor 2 years ago on my '86 when the TC would cut in and out and sometimes not work at all. Worked perfect ever since.

Then just last year, I lost all TC lock-up on the '83 (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=25665&highlight=gizmo) . Turned out to be some relay under the dash. I bypassed this gizmo and fixed the problem. Some here believed the gizmo may have been a cut-out for when the Sub was in 4 wheel drive. I never traced it out.

Also about 3 years ago, the trans was slipping on the '83 ever so slightly. Trans shop said it wasn't the TC and myself and the guys here said it was. I replaced the TC and that cured the problem.

Again, I'm not a tranny expert and would much prefer a manual in all my vehicles! There are others here with much more knowledge. Good luck.

[Subzilla]

Just re-read your explaination of how you adjusted the cable. That doesn't sound right. You should squeeze the black tabs of the cable connector behind the IP, pull out the cable sleeve toward the firewall. Then depress the accelerator pedal down to the floor from inside the cab. The cable will self-adjust. Check for proper adjustment by lightly accelerating down the road. As soon as the 1-2 shift occurs, depress the pedal down to the floor and it should immediately shift back to first. Or have a shop measure the pressure for each gear. Again, experts chime in here!

[neo]

Okay, I tried re-adjusting the TV cable. It is really weird cause right at 33-35 mph it does this shift like thing and then acts as if it is in neutral. If I press on the accellerator harder, it will downshift and start pulling again. There are two things I don't know what they do:
1. The 4 pin (TCC?) connector on the DS near the rear
2. There is another sensor on the right side of the tranny right where the TV cable goes into the top of the part the pan attaches to. THis connector looks like a pressure switch or something, it is on the Passenger side and apears to be connected into a cast oil galley on that side. It has two leads on it, neither is connected to anything, nor is the 4-pin (TCC?) mentioned above connected to anything. Anyone have any suggestions on how/what to connect these to?

THanks again all for the help!!

Neo

[82blazer]

Far from expert but the ATSG indicates a possible worn ban. There should be a plug(connector) for the TCC some where there ( not to point out the obivious) it puts the power into the trans. for the servo and pressure sensors to control lock-up. I would recommend getting the ATSG for the 700r4 1987-1993 it help to understand alot about these things.(got mine from e-bay) As for the P.S. by the TV. cable I'm not sure maybe Robin can help.

[neo]

Many thanks to all for the great information. Still don't have it figured out, but the queen of all things transmission and engine (yes Missy Goodwrench herself) replied to a PM I sent her. She gave me some things to try. What I have found is that it is not (as I previously -erroniously- stated between 3 and 4 that this occurs. It is actually when it hits 3rd it slips. Just like it is in neutral all of the sudden. Doing the test she recommended, it will run along fin in manual shifted 1st, then I let her go to second and that shift is fine. I can spin it up to 35-40 in second without any issue. Then when I manually let it shift to 3rd, the bottom falls out and it is like I am in nuetral. Now, to get it to catch again, I have to really mash on the accellerator and then it will drop back into 1st and spin up very fast. It does great in 1st and 2nd. This truck is pretty messed up and has had multiple powerplants (at least two) and is gonna get a third here really quick. Gonna yank the 6.2 for myself and keep it, put in a 350 I have and (hopefully) get my $$ back out of it so I trade my 350 gasser for the 6.2 I bought it for!! We shall see. Thanks again.
Neo

[chkline856.2]

Hey Neo,
I think I know what is on your trans. I just installed a 700r4 into my truck, and did a similiar arrangement. The 4 pin on the drivers side is the input that locks up the TC, and the 2 pin pressure switch is most likely installed into the 4th gear pressure port. This is what I used on mine, and they sell this kit for hot rods vs manually controlling the TC. This kit uses the pressure on the 4th gear rail to trip the pressure switch which is used to supply power to the 4 pin and lock up the converter. What you will need to do to try this is to run power to one side of the 2 pin, the other side of the 2 pin will run over to the 4 pin, and I belive it is the front left (driver side) pin, and then the back left (driver side) will need to be grounded. Search on ebay for a TC lock up kit, and you will find them, this is where I got mine.