4 +3: General Question
Thread Starter
Instructor
Joined: Aug 2006
Posts: 247
Likes: 0
4 +3: General Question
Hi!
My '89 is a six-speed, but I have always been curious as to how the 4+3 transmission works and haven't been able to find a good description. Am I correct that, if you have the overdrive switched on, that the transmission automatically goes into overdrive if you are driving steadily along in 2nd, 3rd or 4th? Does it disengage overdrive if, say, you have to punch the throttle for some reason?
Thanks!
/s/ Chris Kennedy
My '89 is a six-speed, but I have always been curious as to how the 4+3 transmission works and haven't been able to find a good description. Am I correct that, if you have the overdrive switched on, that the transmission automatically goes into overdrive if you are driving steadily along in 2nd, 3rd or 4th? Does it disengage overdrive if, say, you have to punch the throttle for some reason?
Thanks!
/s/ Chris Kennedy
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The 4+3 is controlled by a number of factors including speed, gear selection, throttle position and coolant temp. Early versions would only have OD in 2nd, 3rd, and 4th, while the later ones could engage OD in 1st.
All have a manual switch that locks out the OD until the ignition switch is cycled. It will automatically downshift out of OD if you punch the gas (depending on how far down you press the pedal) just like a kickdown with an auto trans car. If you hit the throttle in a lower gear, it will not upshift into OD until you shift into 4th.
Here's a neat link to descriptions of how the various years of 4+3 trannies worked.
All have a manual switch that locks out the OD until the ignition switch is cycled. It will automatically downshift out of OD if you punch the gas (depending on how far down you press the pedal) just like a kickdown with an auto trans car. If you hit the throttle in a lower gear, it will not upshift into OD until you shift into 4th.
Here's a neat link to descriptions of how the various years of 4+3 trannies worked.
Last edited by c4cruiser; Oct 27, 2008 at 06:45 PM.
Pro
Joined: Mar 2006
Posts: 663
Likes: 1
yes, cruising wth slow acceleration in 2nd gear you can go into overdrive, and then it stays in overdrive as you shift to 3rd, 4th and 5th. Any hard acceleration and you are out of it.
It isn't as weird as it sounds to drive it right.
It isn't as weird as it sounds to drive it right.
Melting Slicks
Joined: Sep 2008
Posts: 2,360
Likes: 59
From: San Jose California
It is a four speed with a an overdrive unit attached to the tail housing, like a "gear vendors overdrive unit". It's heavy but it is kind of kool for it's time. I had an early version that did not have the 1st gear OD, but did downshift, and then go back into OD when you lifted off the throttle.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
