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12-16-2007, 11:09 AM
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#1 |
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Registered User
Join Date: Mar 2007
Location: Carlsbad, Ca
Posts: 385
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TBI computer swap
I currently have an 8747 computer in my 70 blazer and I was just given a 7747. I was thinking about going with the 7747 in order to control a 700r4. Does anyone know how difficult this would be to swap out and then wire it to control the tranny>
Thanks |
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12-16-2007, 12:56 PM
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#2 |
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Registered User
Join Date: Oct 2003
Location: OC CA
Posts: 1,374
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Re: TBI computer swap
The_goat
8747 and 7747 are cousins, except that 8747 was used in heavy duty trucks, buses, etc. 7747 ECM requires to have ESC module and knock sensor (KS) installed and functioning. KS functionality can be disabled by a disabling a check bit in EPROM. BY default 7747 will try to self test KS on periodic bases by temporarily leaning out mixture and listing for ping. After so many tries SES will come on if it fails to hear a ping. Just pull ESC module and KS from donor and wire it. My guess that 8747 harness might be missing this input wire Pin B7 on ECM. ECM controls when TC gets lockup. //RF
__________________
"The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29)  New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17) Last edited by rfmaster; 12-16-2007 at 02:12 PM. Reason: Schematic |
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12-16-2007, 02:15 PM
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#3 |
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Registered User
Join Date: Mar 2007
Location: Carlsbad, Ca
Posts: 385
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Re: TBI computer swap
rfmaster,
That's exactly what I was looking for. I really appreciate it. |
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12-19-2007, 05:49 AM
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#4 |
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Slots go on anything!
Join Date: May 2003
Location: Richardson, TX
Posts: 5,957
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Re: TBI computer swap
Sounds like a lot of hassle just to control TCC lockup. It may be easier (and cheaper) to control TCC lockup seperately, either with a painless kit or like this: http://www.73-87.com/7387garage/drivetrain/lockup.htm
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12-19-2007, 09:38 AM
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#5 |
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Registered User
Join Date: Mar 2007
Location: Carlsbad, Ca
Posts: 385
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Re: TBI computer swap
I was going to go that route but I'm getting a custom tune anyways for some other upgrades that I have and I was given the computer for free so really it isn't costing me very much at all.
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12-19-2007, 11:27 AM
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#6 |
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Registered User
Join Date: Nov 2007
Location: Franklin Indiana
Posts: 635
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Hey RF Master a question?
A question if you please! I have a 1985 with the "H" code 305. What does that ECM do? I cannot see that it controls anything. The 305 has a Carb. The distributor has vacuum advance. Does it control anything?
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12-19-2007, 01:40 PM
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#7 |
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www.73-87chevytrucks.com
 
Join Date: Dec 1999
Location: Birmingham, AL
Posts: 6,935
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Re: TBI computer swap
An '85 doesn't have an ECM like a TBI setup does. It is the ESC. It was supposed to control spark. Mostly it ended up screwing it up when they went bad...
__________________
Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com |
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12-21-2007, 07:03 PM
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#8 |
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Registered User
Join Date: Mar 2007
Location: Carlsbad, Ca
Posts: 385
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Re: TBI computer swap
can you get rid of the ESC with a tune?
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12-22-2007, 01:51 AM
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#9 | |
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Registered User
Join Date: Nov 2007
Location: Franklin Indiana
Posts: 635
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Re: TBI computer swap
Quote:
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12-26-2007, 11:55 AM
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#10 |
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www.73-87chevytrucks.com
Join Date: Dec 1999
Location: Birmingham, AL
Posts: 6,935
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Re: TBI computer swap
The ESC modifies spark in the controller when detonation occurs.
__________________
Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com |
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