4+3 Relay Bypass Wiring

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Apr 16, 2014 | 05:42 PM

Scott0757

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From: Syracuse NY

4+3 Relay Bypass Wiring

OK. I was planning to perform the eay bypass discussed on this priorost (http://forums.corvetteforum.com/c4-t...n-4-3-a-2.html) but the colors of the wiring on what was indicated to be the Overdrive Relay are not the same as in the factory manual/posted wiring diagram. My factory manula says the OD relay is locaed on the RH inside wheel well, but that is the relay for the blower motor. The image in the above post showsit adjacent to the Fuel Pump reay that uses the sme relay part number. The wiing colors on the Fuel Pump replay appears to be as shown in the manual, so now it appears I must do the bypass by the ECU harness mods.

Can anyone confirm the C4 1984 OD Relay location and the harness wiring colors for the OD relay are the pink-Blk & LtBlue as the connector attached to mine has DrkBrwn, 3 Tan-Blk, and a Green. I could gamble at the A-B-C-D-E wiring positions for the jumper but I want to make sure this is the right relay.

Apr 16, 2014 | 07:43 PM

don hall

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From: SANTA CRUZ CA

may help (?):

https://www.corvetteforum.com/articl...rdrive-bypass/

Apr 16, 2014 | 07:58 PM

Scott0757

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From: Syracuse NY

Quote:

Originally Posted by seabright

may help (?):

https://www.corvetteforum.com/articl...rdrive-bypass/

Thanks but I have this diagram. The relay that others say is for the OD (see link above) does not have these wire colors.. That's why I am confused.

Apr 18, 2014 | 04:05 AM

vetteoz

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From the 84 FSM

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Apr 18, 2014 | 11:46 AM

Scott0757

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Thanks. I have the factory shop manual (FSM) already. As stated above e FSM says the location of this relay is on the right side behind the wheel well. They only relay there is for the blower motor. The two relays on the driver side firewall are said to be the Fuel Pump and the Overdrive relays, but the FSM only shows the Fuel Pump relay there. The wire colors on the schematic are not present on either of these relays and the fuel pump wires appear to be correct. This makes it a bit challenging to know which should be light blue and which should be pink w/blck stripe. That is my challenge.

I still have the see if the console switch is functional as I have not been able to get the Overdrive indictor light to appear on the center panel yet, so something is not working. Will start with the diagnostic chart in the FSM, but I also have a 4+3 with only the 1st (new) and reverse switches (nothing on 2nd or 4th) as this is a replacement tranny.

Thanks for the help

Last edited by Scott0757; Apr 18, 2014 at 11:48 AM. Reason: removed image

May 1, 2014 | 02:00 PM

Scott0757

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IT works!!!!

Happy to report my 84's Nash 4+3 is fully functional and without the throttle valve cable being installed! This car had the Nash removed and I have to find another one to "restore" it. The one I found had only 3 of the 5 connectors and the wires had aged so that the colors are very faded. That said, after troubleshooting the OD switch to the relay and the transmission connections, I learned I had the wrong connector on the 1st gear location so the OD was never going to engage with first appearing open. The solenoid wire had also fallen off sometime during exhaust reassembly too. All that said, took a drive today, got it up to temp and happily found overdrive in gears 2-4! Quite a drop in RPMs. At 55mph in 4th, RPMs went from about 2300 to about 1500. What really surprised my was that 3rd and 4th kicked down out of overdrive when I stomped on it without the throttle position cable even being installed. The ECU must be doing its thing, making the cable redundant. (Must be why latter years did not have one.)
So all is good in Nash land. Will continue to clutch between OD engagement just like when I shift to prolong its life. The first time I engaged it, I forgot and it can be harsh. So no bypass wiring required! Now I can move on to my leaking steering rack....

Last edited by Scott0757; Jun 20, 2014 at 08:39 AM. Reason: typos

May 1, 2014 | 09:58 PM

glava2876

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From: Upstate NY

Quote:

Originally Posted by Scott0757

Happy to report my 84's Nash 4+3 is fully functionla and without the tjhrotle valae cable being installed! This car had the Nash removed and I have to find another one to "restore" it. The one I found had only 3 of the 5 connectors and the wires had aged so that the colors are very faded. That said, after troubleshooting the OD switch to the relay and the transmission connections, I learned I had the wrong connector on the 1st gear location so the OD was never going to engage with first appearing open. The solenoid wire had also fallen off sometime during exhaust reassembly too. All that said, took a drive today, got it up to temp and happily found overdrive in gears 2-4! Quite a drop in RPMs. At 55mph in 4th, RPMs went from about 2300 to about 1500. What really surprised my was that 3rd and 4th kicked down out of overdrive when I stomped on it without the throttle position cable even being installed. The ECU must be doing its thing, making the cable redundant. (Must be why latter years did not have one.)
So all is good in Nash land. Will continue to cutch between OD engagement just like when I shift to prolong its life. The first time I engaged it, I fogot and it can be harsh. So no bypass wiring required! Now I can move on to my leaking steering rack....

I have an 84 and when was following the FSM steps to take out the trans to put in a new clutch PP TO and fly wheel, I could find no TV cable. When I look closely at the trans, someone had changed it to one out of and 85 and my Vette only had 84k miles on it at that point.

I love being able to turn the OD on and off, that gives the best of both world IMO.

May 1, 2014 | 11:15 PM

Scott0757

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I agree and look forward to using it. Mine also had the tranny replaced by the prior owners with a basic saginaw 4 speed so I had to locate a used Nash 4+3, a shorter drive shaft and new pp and disc. So happy it seems to be in good shape.