4+3 OD not working

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Apr 25, 2011 | 07:24 PM

MrMashie

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5th Gear

Joined: Apr 2011

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4+3 OD not working

I just sent my digital cluster out to be rebuilt...My OD was working before I took the cluster out..and now it isn't working at all...the cluster is still out for repairs.. would the missing cluster have any effect on the OD not functioning ? BTW I have a 1987 C4 with a 4+3 tranny

Apr 25, 2011 | 11:26 PM

yakmastermax

Drifting

Joined: Apr 2011

Posts: 1,925

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From: Albuquerque NM

I don't know about how the cluster interacts with the electronic overdrive.

When my overdrive stopped working (1985 4+3) it turned out the be a simple wiring issue under the shifter boot. Solder and 15 minutes fixed it.

Maybe check under there?

Apr 26, 2011 | 06:32 AM

HlhnEast

Safety Car

Joined: Nov 2008

Posts: 4,328

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From: Jacksonville FL

On the 85 I know the cluster controls the cruise but I do not think it does anything with the OD. Its probly just coincidental. More likely the switch has gone bad or a relay. Were you at 145* water temp or higher? Temp sensor functioning properly?

Good luck!

Apr 26, 2011 | 08:04 AM

MrMashie

Thread Starter

5th Gear

Joined: Apr 2011

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Thanks Guys

I'm hoping to have the cluster back in a week or two...what a pain not knowing how much gas you have or how fast I'm going

hard to tell the water temp without it, but it was never an issue before...I ordered a new relay and switch...so when they get here I'll replace them both and see if thats it...I see from the schematic that it's part of the circuit since the OD display is part of the action...

Apr 26, 2011 | 05:41 PM

tequilaboy

Melting Slicks

Joined: Aug 2003

Posts: 3,399

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From: Lakeville MI

The VSS signal goes to the cluster first, then is output as a separate square wave to the ecm.

If no cluster, then there is no vehicle speed signal input to the ecm. O/D upshift velocity criteria is not fulfilled, so O/D will not function.

Apr 26, 2011 | 09:32 PM

MrMashie

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5th Gear

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Thanks

Tequilaboy... thanks for the valuable info...I figured as much...surprised that they advise you of such things when you send it in for repair...

Thanks again

Dave

Apr 28, 2011 | 01:29 AM

coupeguy2001

Le Mans Master

Joined: Sep 2006

Posts: 6,050

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From: Phoenix AZ

2021 C4 of the Year - Modified Finalist

darn, Tequila boy beat me to it.
BUT you can rig up a switch to energize it yourself. just don't bypass the first gear lockout switch.
I have a 4+3 in my 57 Chevy pickup, and it is a manual system. I am Manuel sistem.
Push in the clutch and manuel flips the switch................

Apr 28, 2011 | 07:56 AM

MrMashie

Thread Starter

5th Gear

Joined: Apr 2011

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Thanks Coupeguy.... but...

it seems the cluster is a vital component to the entire system, whose absence causes other issues...ie: the car stalls out, the service engine light is now on, and it all seems related to the missing cluster... at least according to my corvette mechanic. Before removing the cluster the car ran like a bear! So I'm at the mercy of the Cluster guy, who hopefully will have it rebuilt and back to me ASAP. The weather here in the NE has been crap...so it makes it a bit easier to deal with...but those nice days are taking their toll on me :-)