After swapping out the transmission truck will not start

15DOMINICP

MEMBER
1990 GMC SIERRA
200,000 MILES

Okay so my truck is the short bed step side single cab. Currently has a 350 in it and had a five speed manual. Swapped it to a th400 transmission and everything went together and plugged in smoothly. Got a 1994 steering automatic steering column and put it in and plugged everything in. Everything works on the truck powers everything but will not start. I hooked up a starter switch and started it off that and it started right up. So I tried jumping the clutch pedal switch and it still will not start I have tested everything and done research and cannot figure it out or how to by pass the metrical safety switch for it to work.

6 Replies

HMAC300

MECHANIC
48,601 POSTS

Putting the later model steering column in may be the problem. They are both obd 1 but the wiring for certain things may have changed. Especially in ignition. Check wiring on ignition lead from old column to new one. I cannot tell you how to jump safety switches.

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Sunday, March 12th, 2017 AT 8:54 AM

15DOMINICP

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4 POSTS

I mean it is a 1990, but alright thank you.

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Sunday, March 12th, 2017 AT 9:00 AM

HMAC300

MECHANIC
48,601 POSTS

That is what I said in first reply check wiring from column that was removed to wiring in new colum to where they hook up. Purple to purple on other.

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Sunday, March 12th, 2017 AT 9:44 AM

15DOMINICP

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4 POSTS

I did that. And everything has matched up everything is doing what it should, except for sending power to starter.

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Sunday, March 12th, 2017 AT 10:19 AM

HMAC300

MECHANIC
48,601 POSTS

It is the purple wire that goes to start on start cycle. If you have hooked up wiring to transmission then it lies in that area or the column. That is why I said check wiring there due to using a new column.