[kl001]

Been reading all over the net seeking help.

I've got a 92 chevy (5.7 tbi 700r4) which I've recently started to drive again. The tranny never has locked up after 4th since I bought the truck. Yesterday I decided to change fluid, filter, and go ahead and change out the tcc lockup switch ( two wire) also decided to change out the brake switch and got my cruise control back, never has worked until now.

Took it for a test drive shifted to 4th, amazed it finally locked up but then ecm fuse blew and stalled the truck. Replace the fused and the same event happened. Unplugged the 4 pin and drove it home.

This morning I straight wired power to pin A and ground D with a spare connector and it didn't lock at all. The truck originally had a 4.3 tbi, could there a wiring issue with the 5.7 ecm?? Brake switches for the 4.3 and 5.7 are the same to my knowledge. Any ideas? Thanks!

[66GMC]

Originally Posted by kl001

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Brake switches for the 4.3 and 5.7 are the same to my knowledge. Any ideas? Thanks!

NAPA Echlin #SL174.
Yes (assuming C1500 2WD) both engines call for the same switch.



I was thinking that some 700R4's use a vacuum switch, but your truck isn't listed as using this number in the buyer's guide.

NAPA Echlin #TCL100

[SSedan64]

Could be an internal wiring difference but, the Plug uses the same basic pattern. May be a short internally or externally, Harness etc..

Int. Diagrams >> Lockup TCC Wiring
Ext. Diagram >> http://www.hughesperformance.com/pdfs/HP700-R4.pdf

[kl001]

Being as my truck is salvage, I have no knowledge of the trans donor however everyone I've spoke to on phone and internet say that should not matter on the 700 unless someone made direct internal wiring changes. When i dropped the pan, the tcc had never been changed and no wires had been spliced - looked stock. I've seen internal wiring stripped on 700s and tcc check balled or epoxyed over for lockup.

I'm leaning toward a harness problem, spoke when one guy who told me to run 12v to pin A, discard the other pins and try the aldl feature if needed to rule out internal problems and possibly the ecm (with I doubt)

Had another guy mention the 4th gear pressure switch would keep me from lockup, if I used the ecm? Not sure where to go with that.

[kl001]

basically 12v to pin A

jumper to A (ground) and F (TCC) in aldl, might try tommorrow. Couldn't edit pardon for the double post.