Shifting Gears Part 1

Say Goodbye to the 4+3. Say Hello to a Five-Speed

James Miles Sep 16, 2005 0 Comment(s)
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It doesn't take a lot of research to uncover the bad press about theDoug Nash 4+3 manual transmission.

As Richard F. Newton informs us thismonth in "C4 Projects" (page 68), "Chevrolet was working on such a tightdeadline for the Fourth Generation Corvette that there was no time todevelop a new unit specifically for the Corvette." While we're sure GMdid its best when working with such a compressed deadline, reusing partsfor one application that were meant for something else (specifically theCJ-7 and CJ-5 Jeep) can lead to, lets call it, unique driving andmechanical issues.

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The installation starts simply with the removal of the distributor cap.The reason for this is when you remove the transmission, the engine willtilt back. Leaving the cap on will cause your Vette some unneededdamage. Here, you'll see that we've removed the entire unit. This isn'tnecessary, but since we were having some other serious issues (more onthis later), it made the other operation that much easier.

Originally used in the '84-'88 Corvette, the 4+3 was a fickle beast atbest and required a lot of attention. Either you knew how to keep ithappy or you suffered its anger each time you took your C4 out for ajaunt across town. And as I've been told, keeping it happy wasn't aneasy task--but if you took care of it, and serviced it regularly, the 4+3was your best friend. If not, this wonder of automotive technology couldquickly turn into your worst enemy. Look no further than to Team VETTE'spast staffers for a couple of horror stories.

A $10 part that failed was the cause of one past Associate Editor'stotal transmission loss, while the second owner of our own horror story,"The Zombie," went as far as to replace his 4+3 with an automatic beforeselling it to us.

Like it or hate it, you'll find that replacement options are limited.While those seeking to step away from their current gear grinder have apretty good idea why they want to replace theirs, those in favor of thefour-three might already be questioning the reasons for reading thisarticle. The answer is simple: Qualified professionals with the abilityto properly handle the service or rebuild of your transmission arebecoming increasingly difficult to find.

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Meanwhile, the inside of the bellhousing had over 1/4 inch of buildup.

While anybody can rebuild a gearbox, it takes the truly informed to doit correctly. And by "correctly", we mean completed by a technicianwhom you only have to see once in a several-year period. If you findsuch a magician who relies on more than smoke and mirrors to make yourtranny look and feel like new, you might find the cost is enough to makeyou want to pull a "Houdini" on the service bill. And let's not forgetabout the performance enthusiasts. While the box sitting between theframerails of your early C4 may still be the performance wonder of itstime, (even more so after some of the available modifications), itdoesn't take a history lesson to be reminded that this piece ofequipment is getting a little long in the tooth.

So, what is a C4 four+three owner to do? Team VETTE'schoice was to visit with Shafi Keisler, owner of Keisler Automotive, todiscuss the available option of a Tremec 5-speed. If that's enough tomake your brain strip a few gears, read on.

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Speaking of buildup, inside our trans pan, GM's magnet did its job bypicking up all the metal shavings. We can only imagine the condition ofthe internals.

Keisler has long been in the business of giving Corvette owners, as wellas several other brand-name GM competitors, an option for replacement--ahigh-performance replacement at that. If you have questions about Keisler products and things related to this install, e-mail Keisler at

The overall procedure is not a quick one, or for the faint of heart.But, if you're looking to axe your current transmission, originality isprobably not a concern. Thus, be prepared to take an axe to yourtransmission tunnel. For us, the install took quite awhile, but mostlybecause a lot of our extra time was spent gawking at how bad ourworst-case scenario "Son of Zombie" was (see "The Bat's Cave," page 8).Read on for more information on this and stay tuned for the follow-uparticle when we get knee deep in the installation process over atCorvettes by Dreamworks.


SPEC Clutch
Bessemer, AL 35022
Corvette Central
Sawyer, MI 49125
Corvettes By Dreamworks
Sheridan, CO 80110


How To
Check out this Tech Article on the 4+3 transmission in '84-'88 Corvettes. Coverage by Vette Magazine.
James Miles Sep 16, 2005


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