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First Post .. Please help with my 4+3

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Rcpilotlv

Guest
Hi everbody! I just purchased a 85 with the 4+3 manual however I dont believe its working right. At 75 mph my RPM's are 3000. Here is what I do know. I have a console switch for the overdrive which seems to be working, when switch is on I can start out in first and light on dash is out, second through fourth light on dash is on... However from what I have read RPM's are way to high.. It dosn't seem to be working... No upshifting at all.. Rpm's remain the same whether switch is on or off through the gears... Clutch seems to be okay but once in a while I grind going into first(possibly my fault because of really no neutral feeling for gearshift). I had the car up on a lift and the whole underneath of my car really looks brand NEW! No leaks around the overdrive unit at all. Heres the kicker say im in second,third or fourth with overdrive on, if I let off the gas pedal slow down a little bit,then turn the overdrive off it actually seems to downshift.. Its like droping a gear... This really doesnt Make since to me? My car has 101000 miles on it and really is in good shape. Does any body know where I might be able to take my car for repair? A honest mechanic Please? Sorry for the long post...
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Welcome To The Corvette Action Center Rcpilotlv!

Butch, here's some reading for you (in case you haven't already checked it out) on my Doug Nash Information page.

From the way you're describing the problem, you may be deceived into thinking it is in overdrive by what seems like a downshift, but without hearing it myself, I can't say for sure if the overdrive is engaging or not.

My guess is that it's either the switch, (Which in your case could be either located on your console, on the shifter knob, depending on when in the model year cycle it was built.) or it could be the relay for the overdrive which, for manual transmission equipped cars, was located on the same bracket as the fuel pump relay, which is in turn located on the firewall between the brake booster and the distributor. I'd check those two items first before you get into the transmission and overdrive units. ;)

Good luck on your quest to get your Doug Nash 4+3 functioning properly; it can be done. One of the places to check for repairs are The GearZone, and I hear that Four-Speeds by Darrell is doing the DN 4+3 as well now. Parts availability is getting scarce though, be prepared to ante up. ;)
 
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David-F

Guest
It sounda like burnt overdrive clutches so here is what I want you to doat high way speeds turn the overdrive on and off and what I want you to feel for is change in RPMs and also a loose of engine braking, if the O/D clutches burn when you put it into O/D you are only moving forward on the sprag gear which is a one way clutch which means that when you let off the gas the engine rpms drop but the car does not slow down much, but if you turn the switch you will feel what seems like a down shift but when you let off the gas the engine and car slow down together, this is also what you may have felt on the lift because when you turn the O/D off the direct clutches are applied so you can have engine braking if the direct clutches were burned it would slip in reverse. I looks like to me you will have to rebuild the O/D the relay is not the problem if it was the O/D light would not come on(84 to 86). Just let me know if there is anything I can help you with, seeing how it's an early 85 you will have to up date parts in side which will add to the cost of repair, I could repair it for you if you need to have it done but you would have to pull it and ship it.

David Fulcher
 
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Rcpilotlv

Guest
Thanks for the help Guys.... I wont get my relay until tommorow because they didnt have one in stock... Hopefully thats it! If not its probably the unit itself...and it looks like i can order one of those... Please be some thing simple, I love my car!
 
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David-F

Guest
Again if the overdrive engaged light comes on and not the overdrive it's not the relay or the light would not come on only 87 and 88 can have a problem with the relay but still have the O/D light up in the LCD becaused it is operated by the ECM direct.

David Fulcher
 
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Rcpilotlv

Guest
your right david, its not the relay... and i dont think its the switch either.... looks like i will be pulling the unit and sending it to 4 speeds by Darrell.... Not to bad of price after all,Im not going to buy a new car....Hopefully I can pull it this weekend ....Thanks again
 
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David-F

Guest
How much are they going to charge you for the unit? I know because it's an 85 there are a few parts that will have to be updated so that will run the price up a little.

David Fulcher
 
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Rcpilotlv

Guest
I was told shipping(30.00-40.00),Labor 350.00 + parts, and shipping to get it back to me....or they have a rebuilt one for 1675.00 less a 300.00 core.. Im choosing to send mine back...
 
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Rcpilotlv

Guest
Ok guys wish me luck,my car goes in the shop this friday for removal of my OD unit. While they are there im also replacing the clutch... I have contacted 4 speeds by darrell so there expecting my unit.. By the way tuckers GM in las vegas is doing the labor and darrell is doing the rebuilding..Both places seem very nice... anyway if everything goes right im looking at less then 1500.00... Like i said in my previous posts my car is very clean so i dont mind putting the money into it as long as it gets fixed... A new vette is out of the question at 50,000.00.... I will post again when i get it back,it will be down maybe a month.. Any way wish me LUCK!
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Not to worry Mon, evryt'ing gonna be O-K! :gap

I'm sure you'll be satisfied with the work and enjoy many miles of cruising in your Vette. It sound like a "sound" car to as far as the rest of it goes. Good luck Butch. :upthumbs

_ken :w
 
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Rcpilotlv

Guest
Ok guys I did it.... I decided to remove the tranny myself....This is what i did....
1. backed car up on ramps
2. Removed negative battery cable
3. Removed air hose assembly(for exhaust)
4. Removed distributor wires and cap
5. jacked front end up and placed
Jack stands under neath....
6. Removed entire exhaust
7. Supported tranny with jack
8. unplugged the wires(tranny)
8. Removed driveline and brace..
9. unbolted tranny from housing
10. supported oil pan with a jack(4x4 piece of wood)
11. Slid tranny back and lowered

Walla tranny is out, I may have for got a step or two but thats where the haynes manual sure helped out....I am by no means a mechanic. I did this with the help of a friend in my own garage..I saved a total of 13 hours shop labor at 65.00 an hour..(remove and replace) By the way the od unit ways about 60 pounds and will be shiped off monday...We did this in about 4 hours
 

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