700r4 lock-up

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,945
Reaction score
5,695
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Well Damnit for some reason I thought you had an 85 I found a schematic for an 85. Is you're truck a carbureted 49 state car? If so I'd use this as schematic as a reference anyway.

You must be registered for see images attach
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
Sooo…

is this an ECM or a TCC?

knowing this will help decide how I have to approach this.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
I followed instructions to bypass an ESC.

The wire colors matched, so I didn’t even think about it. I’m guessing I was wrong and it’s an ECM.

it starts and runs fine. It even revs. It has no issue in first gear, But after it shifts I can’t drive the truck at more than 10% throttle or it loses all power.

as soon as I back off to about 10% throttle I get all the power back and the truck continues to drive, without issues.

If I keep it at less than 10% throttle, Eventually I can get up to 55-ish, but at any point if I push the throttle further than about 10%, all power goes away & as soon as i back off the throttle, all power comes back.
 
Last edited:

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,945
Reaction score
5,695
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Sooo…

is this an ECM or a TCC?

knowing this will help decide how I have to approach this.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
That's the ESC controller.
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
Sorry…

I meant ESC, not TCC.
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
So does that mean I do not have an ECM?

this box is mounted up under my dash behind the glove box.

If I do not have an ECM, why does my truck lose all power upon shifting.
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
If I do not have an ECM, does the ESC have “ANYTHING” to do with shifting?
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,945
Reaction score
5,695
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
This is 100 percent gut feeling and just a guess, but humor me. Make a mark on the manifold and distributor base so you can put things back if you have too.Now loosen the distributor hold down and twist the distributor body itself 1/2 inch counter clockwise, lock the distributor down and take a test drive. Is it better ? Twist it a little more, post your results. I'm theorizing you have your initial timing wayyy to low when it shifts, and you lose all the centrifugal and you step into the throttle and lose all your vacuum advance your timing is so slow it won't run.
 
Last edited:

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
This is 100 percent gut feeling and and just a guess, but humor me. Make a mark on the manifold and distributor base so you can put things back if you have too.Now loisen the distributor hold down and twist the distributor body itself 1/2 inch counter clockwise, lock the distributor down and take a test drive. Is it better ? Twist it a little more, post your results. I'm theorizing you have your initial timing wayyy to low when it shifts and you lose all the centrifugal and you step into the throttle and lose all your vacuum advance your timing is so slow it won't run.
Are you sure it’s not an ecm.. I have a 1990 ecm in my scrap pile that looks just like that... OP can I see your computer side ways to see the terminal? If you open the screws on one side do you open up to reveal a narrow chip with a blue cover that is pushed into the contacts?
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Gm transmissions didn’t use electronic controls until the early 90s but they definitely could have electronic components such as something that interacts with a vacuum switch for lockup on a tcc
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Nvm that’s a lot smaller than I thought same general shape as what I thought. Ur good esc.
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
I ordered the Painless 700r4 kit.
You must be registered for see images attach
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
There were other, less expensive, kits, but they seemed to be more about bypassing than replacing.

… and several of the other kits had a manual switch, which I don’t want.

for some reason, I couldn’t buy direct from Painless and had to go through Summit.
 

BJedi76

Full Access Member
Joined
Nov 7, 2019
Posts
152
Reaction score
19
Location
Soldotna, Alaska
First Name
B.J.
Truck Year
1986
Truck Model
GMC Sierra Classic 1500 4x4 SWB
Engine Size
305”
Why does this kit come with an external pressure switch?

Can I not get the internal pressure switch(es). I haven’t even looked, yet.

I assume that’s with the little silver canister that screws into the transmission, is for.

what is the point of bypassing things that are already there?

Did I buy the wrong kit?
I (apparently wrongly) assumed that this kit was simply, modern replacement parts.

everything in the kit seems to simply replace things that I already have, except that little silver pressure canister.

Anyone care to explain this to my dumb ass..?
 

Latest posts

Forum statistics

Threads
41,856
Posts
903,621
Members
33,370
Latest member
mitchell1128
Top