'88 4+3 Questions
Thread Starter
Cruising
Joined: Apr 2008
Posts: 13
Likes: 0
From: colo. spgs. colo.
'88 4+3 Questions
My '88 with the 4+3 transmission has popped out of 2nd under heavy torque conditions( down hill medium to medium-high r.p.m.). My mechanic listed off a couple of possibilities that both sounded like a new tranny is in order if it gets worse. Is this common? are used 6 speeds available? ( I don't like the overdrive very much) How much should I pay for a used 6- speed? Are they hard to install??? Are the 4+3 Trannys problems in general? Any help will be GREATLY appreciated, KARL
Safety Car
Joined: Apr 2008
Posts: 4,284
Likes: 1
From: Whitehall Pa.
I have a 84 with a 4+3 and had to replace the overdrive in it last year. It's hard to find someone familiar with them. The 4 speed isn't too much of a problem but when you mate the two back together you have to be careful. Don't destroy the boot that the linkage runs through. I've been looking for a year for one of those. There are a few people that are knowledgable. Darrel at 4 Speeds is good. Give me a PM and I'll give you his number if you want it. Also if you ever need to replace the overdrive get a used one or a rebuilt. I tried to have mine redone but there aren't any parts and the main bearing in them can go and take out the case.
Drifting
Joined: Oct 2005
Posts: 1,457
Likes: 9
From: Minneapolis MN
When the previous owner of my car had that problem, I believe he simply replaced the clutch. I'd get a second opinion from another mechanic, preferably one that specializes in Corvettes and is familiar with the 4+3.
Thread Starter
Cruising
Joined: Apr 2008
Posts: 13
Likes: 0
From: colo. spgs. colo.
thats what my girl friend said "maybe it's the clutch" I hope! the clutch seems OK to me when I drive it. I think I will take it easy and stay away from HARD down shifts. Thank You very much!!! KARL
CF Community Team
Joined: Oct 2004
Posts: 19,371
Likes: 5,251
From: Cape Cod, Mass.
2025 C6 of the Year Finalist - Unmodified
2025 C8 Z06/7/E-Ray of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2021 C8 of the Year Finalist Unmodified
2020 Corvette of the Year Finalist (performance mods)
2019 C1 of Year Winner (performance mods)
2017 Corvette of the Year Finalist
2016 C2 of Year
2015 C3 of Year Finalist
My 85 4 plus 3 was doing the same thing in second gear mostly on decelleration. It's most likely the second gear slider/synchro. I had mine rebuilt by someone familiar with these last year and it has been terrific ever since. Consult with SK performance out of New York State for parts and info. They can also recommend 5 or 6 speed replacements. I'm glad I stuck with the 4 plus 3.
Last edited by capevettes; Apr 16, 2008 at 09:19 AM.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
My 85 4 plus 3 was doing the same thing in second gear mostly on decelleration. It's most likely the second gear slider/synchro. I had mine rebuilt by someone familiar with these last year and it has been terrific ever since. Consult with SK performance out of New York State for parts and info. They can also recommend 5 or 6 speed replacements. I'm glad I stuck with the 4 plus 3.
The slider/synchro sounds like it's bad. It may also be the shifter fork in the side plate that is worn or the detent spring that hold the fork in place.The 4-speed portion is actually a Borg Warner Super T-10 and it is relatively easy to work on. But there are specific steps in the separation of the OD unit from the 4-speed case so make sure you find somebody that is knowlegeable regarding the 4+3 or get a FAS for your year and have that available to a transmission tech.
Of course with the tranny out of the car, it's a good time to check the clutch disc to see if it's in need or replacement. Or maybe just do a new clutch/pressure plate/throwout bearing anyway while the tranny is out.
