1970 Tcs, Th400

[D S.]

While under the car trying to resolve a starter issue (in another post) I noticed a wiring harness on the driver's side bellhousing down to near the transmission that has a 'T' configured round electrical pigtail. There is nothing on the driver's side of the transmission to plug it into. The transmission was rebuilt three years ago so nothing should have been altered. My assembly manual shows a similar TCS harness that's supposed to plug into a switch on the side of the transmission. Was this plug and switch just for four-speed cars?

Thanks,
Scott Sims
Texas Chapter

[Harmon C.]

Re: 1970 Tcs, Th400

Scott
I have a plug and switch on my 73 TH-400 in that location I think but I will check today to be sure.

[Martin N.]

Re: 1970 Tcs, Th400

My 74 TH400 has a swicth on the drivers side of the trans and it's for the trans kick down circuit I believe. On a 1970 I'm not sure unless it's like you said, part of the harness for a 4 speed car. Hopefully someone will chim in that has a 1970 4 speed.

Marty

[D S.]

Re: 1970 Tcs, Th400

Thanks, Lyle and Martin. I'd like to see a photograph so I will know exactly what I am looking for and where. That means if I don't have what's supposed to be there then I have to find it to buy it. I know a lot of main wiring harness trunks had sub-harnesses and plugs left open for options and such but it bothers me to see a plug just hanging on clips that seem to go to nothing. In the assembly manual there is a canceled kick down switch shown in a schematic....maybe that was what that plug was for.

[Harmon C.]

Re: 1970 Tcs, Th400

I don't have a picture but I just looked at the switch and it is near the back of the transmission on the drivers side just ahead of the curve at the rear of the pan about one inch above the pan on a 73.

[Terry M.]

Re: 1970 Tcs, Th400

I'm pretty sure it is in the same place on TH400 1970-72. I have to wonder if the rebuilder left off the switch on the transmission. That oil port is usually pluged with a small (1/8-inch ??) pipe plug on those units without TCS. If memory is right it is a port to test line pressure, but it has been a while since I worked on a TH400.

[D S.]

Re: 1970 Tcs, Th400

Thanks, Lyle and Terry. I have the car on jack stands now so I'm ready to go switch searching although that harness does not seem that long. That switch may have been left off during rebuild but it's been too long ago to expect it to be still around. And they don't come up too often on eBay. When one did a while back I didn't think I needed it then.

[Patrick H.]

Re: 1970 Tcs, Th400

It's not an uncommon switch, and a similar one was used in other GM cars.

When the trans in my Cutlass was previously serviced (prior to my ownership) the switch was replaced with a bolt. I had the local trans shop watch for one, and about 6 months later they found the correct switch on a trans that came throught their shop. That switch is now on my workbench, ready to be installed on my Cutlass soon.

So, they're out there. Junkyards would be another source.

Patrick

[D S.]

Re: 1970 Tcs, Th400

Hey, Patrick! How goes it?
I did see one steel bolt on the driver's side that didn't appear to be an integral part of the transmission case. I may do what you did....just wait until one pops up. In just about every salvage yard I've been to the car bodies are sitting on the ground and if the transmissions are in a pile somewhere the owners won't let me pull individual parts off them.

[Martin N.]

Re: 1970 Tcs, Th400

SCOTT-

Here's 2 (not very good, it's tight under there!) pictures of the trans switch on my 74 TH400, hope this helps.

Marty

[D S.]

Re: 1970 TCS, Th400, Found it!

Found it! Thanks for the photos, Martin. And to the rest of you for trying to lead the blind. The switch was "hiding" just above the exhaust pipe and what I assume the emergency brake bracket. Using two needle nose pliers, a coat hanger hook, and a lot of luck I managed to bend the pigtail head toward the switch and using the only two fingers I could squeeze in there it just managed to position itself onto the blades. Using needle nose pliers again, I was able to push the pigtail firmly onto the switch. Note that I could use only two fingers, a coat hanger wire, and needle nose pliers. What's that got to say about limited space?
Thanks, all.