The 91 c3500 with 5.7 or 7.4 only had the option for a 4L80e. Count the number of transmission pan bolts to be sure it hasn't swapped.
The 91 c3500 with 5.7 or 7.4 only had the option for a 4L80e. Count the number of transmission pan bolts to be sure it hasn't swapped.
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I was hoping that might be the case, I haven't seen the truck in about 3 years (He was a previous boss and I work somewhere else now) I asked him to send me some pics of the tranny pan and get the numbers off of the ecu, but his wife went in the hospital yesterday, so he has bigger things on his mind...Originally Posted by brian617
I really appreciate the responses
He finally got back to me, and he does in fact have the 4l80. Thank you for helping
91 was was the first year for the 4L80E and '7060 computer.
I see a couple options:
1. Completely re-pin the '7060 that is currently in the truck to use the 1993 computer, making sure the 4L80E wiring is correct (or add a new 4L80E harness) for the 1993 transmission.
2. Add the 93 computer to control the 93 4L80E only. The 93 computer will need the following signals to operate a 4L80E: VSS, TPS, CTS, and RPM (DRP). You could leave the original 4L80E connector unplugged, and add a new 4L80E harness from the 93 computer. A custom chip is also needed for the 93 computer. You could solder splice the needed wiring for the 93 computer from the 7060 harness.
dave w
If he already has a 4L80E in the truck , simply swap the transmission.
Worst case senerio is the 1991 truck has the old 4L80E plug held to the transmission by a single bolt in the center and your transmission has the updated snap on plug. There are wiring differences that will have to be addressed if this is the case but still a bolt in swap seeing's as you said he actually has a 4L80E.
Wiring for both style plugs , click to enlarge : Attachment 8844
If both transmissions have the early bolt on plug , swap the trans and go.
TOM
1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
1992 S-10 434 SBC/Tremec - '7427
1986 Monte Carlo SS
1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
1980 Z-28 496/700R4
1979 Corvette 496/700R4
1977 Olds 98 Regency 403/700R4
I finally got into that yesterday, He did in fact have the old style plug and the new transmission had the updated one. Thank you Nasty-Z for the wiring diagram. Everything bolted up without a problem and the wiring took about another 20 minutes to go through.
Transmission works perfectly and shifts through all gears as it should.
I appreciate all of the advice and willingness to help
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