7 speed `84 Corvette?? - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 9 (permalink) Old 09-02-2010, 01:51 PM Thread Starter
Former Super Moderator
 
Rukee's Avatar
 
Join Date: Feb 2007
Location: South Central Wisconsin
Posts: 9,919
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
7 speed `84 Corvette??

A customer just bought last night an `84 corvette with the crossfire (puke) fuel injection and 4 speed. On the console it reads 4+3 overdrive. Before he bought it he was telling me it was a 7 speed, so what gives? How do you shift into the 3 overdrive gears? Just appears to be a 4 speed shifter and gear knob just shows the 4 gears and reverse. I see a rocker switch labled overdrive on the console but it doesn't appear to do anything after 4th. Is there anything we should know on how to get those 3 overdrive gears?? Do you have to be going so fast before it works?? Or flip the switch and change gears with the shifter?? We just don't know.
Rukee is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 09-02-2010, 02:22 PM
 
jetstang's Avatar
 
Join Date: Nov 2008
Location: Niceville, FL
Posts: 3,376
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Garage
It lets you turn on the OD in 2, 3 and 4, so 7 speed. My brother had one, I never drove it so don't know when it works. I think it's a tailshaft mounted OD, like a gear vendors, which is hydraulic and you have to be at 55 for it to come on.

Burning rubber since 1982!!
My photobucket, lots of dif car pics.
http://s411.photobucket.com/home/jetstang
jetstang is offline  
post #3 of 9 (permalink) Old 09-02-2010, 02:38 PM
 
Mad_Dan_Eccles's Avatar
 
Join Date: Mar 2006
Posts: 47
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Rukee View Post
Before he bought it he was telling me it was a 7 speed, so what gives? How do you shift into the 3 overdrive gears? Just appears to be a 4 speed shifter and gear knob just shows the 4 gears and reverse. I see a rocker switch labled overdrive on the console but it doesn't appear to do anything after 4th. Is there anything we should know on how to get those 3 overdrive gears?? Do you have to be going so fast before it works?? Or flip the switch and change gears with the shifter?? We just don't know.
This is a rather old fashioned way of getting longer legs on a car. Overdirves were once much favoured by British car makers to rpovide a more relaxed cruise, though they have been largely replaced by five or six speed gearboxes

Basically what you have is a small epicyclic gear box added to the rear of the stardard 4 speed box which gives you about a 2/3 reduction in revs in 2,3and 4 for any given road speed.

On an '84 Corvette this overdrive unit is tied into the engine management systems if memory serves, though the switch you describe may be intended to bypass the management system.

Check the operation by accelerating to a steady cruise in top and then flick the switch to engage the overdrive - you should see an an immediate reduction in revs at the same speed if everything is working. There shoudl also be a lamp that comes on when the OD is engaged

If the OD is not working there are several posibilities - the switch could be bad and I think there is a relay in the system that can go kaput and prevent the overdrive from engaging as well as a whole host of possible mechanical reasons it won't come on.
Mad_Dan_Eccles is offline  
 
post #4 of 9 (permalink) Old 09-02-2010, 04:11 PM
 
jetstang's Avatar
 
Join Date: Nov 2008
Location: Niceville, FL
Posts: 3,376
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Garage
I think there's a wire inside the shifter from the knob that gets severed and makes the OD inop.

Burning rubber since 1982!!
My photobucket, lots of dif car pics.
http://s411.photobucket.com/home/jetstang
jetstang is offline  
post #5 of 9 (permalink) Old 09-02-2010, 04:36 PM Thread Starter
Former Super Moderator
 
Rukee's Avatar
 
Join Date: Feb 2007
Location: South Central Wisconsin
Posts: 9,919
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
Awe, figured it out. You need to use the rocker switch to enable OD operation, then starting in second, you can push in the center on top of the shifter (the part that shows were the 4 gear's pattern are and reverse) and it will get the OD. Then push it again and shift to third, then push the shifter button and OD in 3rd, etc. Kinda cool, almost like a split rear end, but not meant for racing that's for sure!!
Thanks everyone for the responses!!
Rukee is offline  
post #6 of 9 (permalink) Old 09-04-2010, 10:38 AM
roy
 
Join Date: Jun 2010
Location: Ontario, Canada
Posts: 96
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Gear Vendors over/under drive!

Made by Gear Vendors they are guranteed to 1,000hp & on an auto car they can knock considerable time off your 1/4 mile times, if you know how to use it.
I've got one behind a C-4 & on a 2.5 mile raceway, we knocked almost 6 seconds off our track time, instead of that big RPM drop between gears, it allows you to keep the motor in its sweet spot all the time.
cost - 2500 & up
roy is offline  
post #7 of 9 (permalink) Old 09-05-2010, 08:25 AM
 
silversport's Avatar
 
Join Date: Mar 2007
Location: Chicagoland, USA
Posts: 1,274
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Doug Nash...Corvette 4 + 3 Overdrives
Bill

**QSM/RH/A4/17**1 of 52**
Like what you've got?...Thank a Vet!
silversport is offline  
post #8 of 9 (permalink) Old 09-05-2010, 10:15 AM
roy
 
Join Date: Jun 2010
Location: Ontario, Canada
Posts: 96
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
i stand corrected

Nash's unit, eh, almost exactly the same, wouldn;t be surprised if they;re made by GV, but, your right, Sold & serviced by Doug.
GV guarantees their units to 1200hp & on the dyno shows just how efficent the unit is, driveline loss - 4 hp per 100hp!
roy is offline  
post #9 of 9 (permalink) Old 09-05-2010, 02:41 PM
 
Join Date: Oct 2007
Location: Long Island NY
Posts: 4,702
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Garage
A good friend of mine made a nice business from repairing the 84 Gayvette 4+3 OD transmissions.....



Eric Animal is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > Off Topic Discussions > Racing and Kill Forum

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
gtols2 vs corvette c5 z06 vs corvette c6 hemipower 2004-2006 GTO General Discussion 4 05-22-2009 11:15 AM
Corvette... thecommish16 The Lounge 15 02-21-2007 08:06 PM
Corvette Cruise In C5ORGTO National Events 1 06-29-2006 08:22 PM
Corvette :( The_Goat Racing and Kill Forum 2 05-27-2006 05:24 PM
Corvette SS Noraku_6.0L Audio & Video Clips 6 03-30-2006 06:45 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome