4+3 Diag?
Thread Starter
Safety Car
Joined: Jan 2003
Posts: 4,902
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From: Tavernier Fl
4+3 Diag?
I have searched the archives on this topic and am still unsure where to start. My overdrive has not worked since I got the car, if i am driving w/o the overdrive on there is a whine (carrier bearing?)If i push the o/d button it goes away but the car does not shift into o/d. When driving with overdrive on, then when not on the gas(coasting) i push button there is a bam and it shakes the car like it is trying to downshift or something, also when downshifitng with o/d on it almost seems to be in neutral until i give it some throttle then it will bring the rpms up. I believe this thing is fried but is there anything i can do to diagnose it before replacing it-i have located one out of an 86' for a good price and I think it will work in my 87' but I am just exploring all my options
Thanks!
Ben
Thanks!
Ben
Safety Car
Joined: Jun 2003
Posts: 4,510
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From: Coconut Creek FL
Re: 4+3 Diag? (belmor)
Ben,
The whine you hear is the carrier bearing (I am in the same boat you are with my 84) The issue with the OD going in and out and banging the whole car is most likely internal...such as the clutch\friction plates etc...mine does the exact same thing as yours...I don't know of any diagnostic tools one can use due to the nature of the beast...I am pretty sure the 86 and 87 OD units are the same...the earlier units had a different side plate and electronics on it...
Hope this helps! :seeya
The whine you hear is the carrier bearing (I am in the same boat you are with my 84) The issue with the OD going in and out and banging the whole car is most likely internal...such as the clutch\friction plates etc...mine does the exact same thing as yours...I don't know of any diagnostic tools one can use due to the nature of the beast...I am pretty sure the 86 and 87 OD units are the same...the earlier units had a different side plate and electronics on it...
Hope this helps! :seeya
Team Owner
Joined: Mar 2000
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From: Boston, MA
Re: 4+3 Diag? (byte_me)
86 and 87 are identical except for 1 thing. The side covers are differnt. 1986 was the only year not to have a 1st gear switch on it. You can easily swap the covers though. I did just that. I put my 87 side cover onto an 86 gearbox. Works perfect.
The only other difference is if the unit is an MH5 (0.60:1 ratio) or MK2 (0.68:1 ratio) overdrive unit. If you don't use the same one as before your little Upshift light will come on at odd times and might annoy you. Otherwise it won't really matter.
The only other difference is if the unit is an MH5 (0.60:1 ratio) or MK2 (0.68:1 ratio) overdrive unit. If you don't use the same one as before your little Upshift light will come on at odd times and might annoy you. Otherwise it won't really matter.
Thread Starter
Safety Car
Joined: Jan 2003
Posts: 4,902
Likes: 19
From: Tavernier Fl
Re: 4+3 Diag? (byte_me)
I kinda figured it was shot, I think I am going to get this one from the forum member that emailed me-he took it out of an 86' in 92 and its been in storage, the od if is fine but the trans is bad still for $100 i dont think i can go wrong
Ben
Ben
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Re: 4+3 Diag? (belmor)
I would also check your overdrive relay near the firewall under the wiper motor. Over time the wire ends become exposed and short out which can cause the jumping in and out of OD.
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Re: 4+3 Diag? (belmor)
what do you have to do to access this relay?
It isn't behind the battery. Those are the MAF power and burnoff relays. It is under the wiper motor. On a 4+3 car you'll have 2 identical relays at that location. One is the fuel pump and the other is overdrive. Unplug one and try starting the car. If the car runs then you got the right one. If the car doesn't run its the other one. The OD is usually the one closest to the firewall.
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Re: 4+3 Diag? (belmor)
The relay - definitely check that first. I had a problem with my O/D. The problem was the wire harness that Scorp mentioned. If you find that the wire harness is securely attached to the relay, then I've heard it's $10 for a replacement relay.
One more thing. My O/D was going in and out recently and it turned out to be a wire that's tightly strapped to the gear shift. The strap actually cut the wire. The wire carries the 'close' from your O/D switch on the top of your shifter. Oh - shoot - you've got an '84? I don't remember where your button is. Something to think about while you're testing. Both options are
cheap fixes!
Good Luck.
One more thing. My O/D was going in and out recently and it turned out to be a wire that's tightly strapped to the gear shift. The strap actually cut the wire. The wire carries the 'close' from your O/D switch on the top of your shifter. Oh - shoot - you've got an '84? I don't remember where your button is. Something to think about while you're testing. Both options are
cheap fixes!
Good Luck.
Thread Starter
Safety Car
Joined: Jan 2003
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From: Tavernier Fl
Re: 4+3 Diag? (86VetteBill)
Hey guys,
I got up this morning and checked the relays, the fuel pump one looks good, but the relay for my o/d is a mess, the insulation has receded 1/2-3/4 of an inch and it is a corroded melted mess, how do I go about reparing this? the only ideas I have are to a.) find a good plug off another car and splice it in or b.) get the pin out for the relay and hard wire it
Thanks
Ben
I got up this morning and checked the relays, the fuel pump one looks good, but the relay for my o/d is a mess, the insulation has receded 1/2-3/4 of an inch and it is a corroded melted mess, how do I go about reparing this? the only ideas I have are to a.) find a good plug off another car and splice it in or b.) get the pin out for the relay and hard wire it
Thanks
Ben
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Re: 4+3 Diag? (belmor)
Is the connector itself a molten mess? If you can I would hit the wires with some brake cleaner to clean off whatever goo you can and then possible re-pin the connector. The tools to remove and repin the wires are relatively cheap. On mine I was lucky enough to be able to clean the wires of and wrap each one with electrical tape as they had not pulled out of the connector, just the insulation had receeded.
Thread Starter
Safety Car
Joined: Jan 2003
Posts: 4,902
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From: Tavernier Fl
Re: 4+3 Diag? (scorp508)
It does not appear that the wires are out of the connector, i went ahead and bought a new relay as well, this weekend I will see if I can clean it up and get it to work, it may not fix the problem but it will be pme less thing that could be causing it. This is the 4th relay ive replaced in the month ive had the car-may just be the problem, i will let you know
Ben
Ben