4+3 transmission
Thread Starter
Advanced
Joined: Feb 2008
Posts: 87
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From: sacramento CA
4+3 transmission
Ok so i just bought a 1988 corvette and frankly i hate the damn 4+3 transmission. does anyone no where i can get a 6 speed tranny that will fit easy to my L98 and if so how much do they run
Navigator
Joined: Feb 2008
Posts: 9
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so uh, other than the general "the overdrive breaks!" complaint, what's the problem with this transmission?
from what I've read you're golden if you just use it as a normal 4speed manual and engage OD only on highway.
Just picked up an 86 with this transmission so I'm just wonderin.
from what I've read you're golden if you just use it as a normal 4speed manual and engage OD only on highway.
Just picked up an 86 with this transmission so I'm just wonderin.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The Doug Nash 4+3 tranny was behind the 87-88 Callaway Twin turbo cars and it worked just fine. Those motors put out close to 350HP and 465 ft-lbs of torque.
The 4-speed portion of the tranny is a Borg-Warner Super T-10 unit and they have been behind all sorts of high perofrmance motors. The key to long life in the 4+3 is regular maintenance.
I would change the gear oil in the 4-speed every coupe years using a good GL5 rated 80W-90 or 75W-90 oil. At the same time, change the ATF fluid (Dexron II or III) in the OD and toss in a new filter at the same time.
My 87 has the 4+3 and it has survived autocross events, track days (I don't use the OD for track days) and a few drag strip passes. Not a whimper from it.
But for transplanting a different trans, the ZF6 will fit and you can use the hydraulics. Figure around a couple thou for a complete assembly in good shape (trans, new clutch, pressure plate and flywheel) and driveshaft mods. There is a Richmod Gear 6-speed made specifically for C4's but they run over $3500 new. In either case, you will have to do some cutting in the floorboard tunnel for shifter clearance.
Just do a search and you can find lots of tech info on a awap.
The 4-speed portion of the tranny is a Borg-Warner Super T-10 unit and they have been behind all sorts of high perofrmance motors. The key to long life in the 4+3 is regular maintenance.
I would change the gear oil in the 4-speed every coupe years using a good GL5 rated 80W-90 or 75W-90 oil. At the same time, change the ATF fluid (Dexron II or III) in the OD and toss in a new filter at the same time.
My 87 has the 4+3 and it has survived autocross events, track days (I don't use the OD for track days) and a few drag strip passes. Not a whimper from it.
But for transplanting a different trans, the ZF6 will fit and you can use the hydraulics. Figure around a couple thou for a complete assembly in good shape (trans, new clutch, pressure plate and flywheel) and driveshaft mods. There is a Richmod Gear 6-speed made specifically for C4's but they run over $3500 new. In either case, you will have to do some cutting in the floorboard tunnel for shifter clearance.
Just do a search and you can find lots of tech info on a awap.
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
My 4+3 works great.
From what I have seen, the problems with the 4+3 transmission were all from neglect, abuse and just plain not knowing how to shift it correctly. Using the clutch to engage it and disengage it are all you need to do to make it operate correctly. It should only be engaged at highway speeds and when the car is at normal operating temperature. Change the fluid and filter every 30,000 miles and it should be fine. This transmission was not designed to be a 7 speed racing transmission. I have it in my 85 and love it. It has always been used correctly and has never had any problems.
Drifting
Joined: Oct 2006
Posts: 1,694
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From: Beaverton Oregon
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Drifting
Joined: Oct 2005
Posts: 1,457
Likes: 9
From: Minneapolis MN
What do you hate about it? Why did you buy a car with a tranny you hate? I like my 4+3, a 5speed or 6 speed might be better, but I have a 7 speed right now and I have fun playing with it. Just wondering - why do you hate it?
Thread Starter
Advanced
Joined: Feb 2008
Posts: 87
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From: sacramento CA
well the thing with it is that its kinda rough to shift its not smooth. im checking my tranny fluid today. maybe its because i just got the car and am not use to the 4+3 and hydrolic clutch. cause the person i bought it from has no problem driving it.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
only thing wrong with the 4+3 is the "computer management"...and that is WAY wrong...minor electrical mods take the ecm out of the game.
wouldn't trade my "super T-10 + o/d" for anything other than that aftermarket 6-speed that has 5th gear 1:1 and only one o/d --and thats a "maybe" (not sure i wanna shift more times, and have so much torque on tap that closer 1-5 gearing likely would add nothing)
wouldn't trade my "super T-10 + o/d" for anything other than that aftermarket 6-speed that has 5th gear 1:1 and only one o/d --and thats a "maybe" (not sure i wanna shift more times, and have so much torque on tap that closer 1-5 gearing likely would add nothing)
Melting Slicks
Joined: Nov 2004
Posts: 2,799
Likes: 2
From: Cape Coral FL
only thing wrong with the 4+3 is the "computer management"...and that is WAY wrong...minor electrical mods take the ecm out of the game.
wouldn't trade my "super T-10 + o/d" for anything other than that aftermarket 6-speed that has 5th gear 1:1 and only one o/d --and thats a "maybe" (not sure i wanna shift more times, and have so much torque on tap that closer 1-5 gearing likely would add nothing)
wouldn't trade my "super T-10 + o/d" for anything other than that aftermarket 6-speed that has 5th gear 1:1 and only one o/d --and thats a "maybe" (not sure i wanna shift more times, and have so much torque on tap that closer 1-5 gearing likely would add nothing)
No problems at all with my 4+3 (and I powershift it)
Instructor
Joined: Jan 2008
Posts: 163
Likes: 1
From: Idianapolis Indiana
I have a 4+3 in the 85. I thought it was a weird setup but it worked, and I liked it...... until it failed. So now I'm saving up for a richmond. If I didnt have a burning dislike of stock stuff I would probably retain it but once you have over 500 lb torque what are ya gonna do? Know what I mean.
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
I have a 4+3 in the 85. I thought it was a weird setup but it worked, and I liked it...... until it failed. So now I'm saving up for a richmond. If I didnt have a burning dislike of stock stuff I would probably retain it but once you have over 500 lb torque what are ya gonna do? Know what I mean.
Advanced
Joined: Feb 2008
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From: Southlake Texas