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Old 09-09-2018, 04:22 PM
 
Location: Southwest
2,607 posts, read 2,334,698 times
Reputation: 1976

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Back in '84 or '85 the new generation Corvette had a manual transmission called the 4+3, or something like that. IIRC, it had 2 modes but either way a person only shifted 4X, including first gear. I think first gear was the same for either mode but gears 2 to 4 had ratios that depended on what mode the driver was in. One mode had lower gearing, the other mode had higher gearing.


I vaguely this transmission being cancelled due to reliability issues. Is that correct?
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Old 10-18-2018, 01:30 PM
 
Location: Riverside Ca
22,146 posts, read 33,639,819 times
Reputation: 35439
The 4+3, better known as the Doug Nash was basically a four-speed manual transmission with an electro-hydraulic online overdrive auxiliary unit where the typical tail shaft cone would reside. Normally the OD worked in the upper three gears, hence the name "4+3”. It’s kind of like the 85 Volvo transmissions with a Laycock/DeNormanville/Gearvendors auxiliary overdrive units or trucks like mine with a Gearvendors overdrive which is basically a laycock . Or like a brownie transmission or US Gear.
This unit was used to bring the CAFE fuel economy up in the years that GM was trying to get their averages up.

The reason they were “unreliable” was because most people who bought them didn’t understand them, usually did not maintain them correctly and probably misused them.

I have a Gearvendors overdrive. Basically as soon as I get over 35 mph I can have each gear on my ZF6 as a overdrive gear. I had 155,000 miles on it before I had to replace it. The only thing that was wrong was the cone clutch was wearing out. I didn’t have time to buy a rebuild kit. I just called Gearvendors and they sent a rebuilt unit with exchange.

If you understand how a auxiliary unIt works it will last a long time if it’s not abused or neglected.
FYI on my Gearvendors I have to change the gear oil every 5,000 miles. But I have to change the engine oil at that time also. It adds about $20 to my oil change costs. I expect 200,000 miles before I need to do anything in repairs/rebuild

The ZF6 was a better less complicated transmission
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Old 10-18-2018, 06:44 PM
 
Location: Southwest
2,607 posts, read 2,334,698 times
Reputation: 1976
@electrician4you: Thanks. I drove the successor transmission in a 'vette. A person shifted either 4 or 6 times. It was either gears 1 through 6, or 1 and 4 through 6. I thought the ratios in 1 through 4 were too close. Thinking about it now causes the term gimmick to come to mind.
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Old 10-18-2018, 06:51 PM
 
2,211 posts, read 1,581,707 times
Reputation: 1668
Quote:
Originally Posted by curiousgeorge5 View Post
Back in '84 or '85 the new generation Corvette had a manual transmission called the 4+3, or something like that. IIRC, it had 2 modes but either way a person only shifted 4X, including first gear. I think first gear was the same for either mode but gears 2 to 4 had ratios that depended on what mode the driver was in. One mode had lower gearing, the other mode had higher gearing.


I vaguely this transmission being cancelled due to reliability issues. Is that correct?

84 or 85 Corvette... LOL. So this was an actual, real, three-pedal manual?


I've always wanted to buy a C4 Corvette but I feel like I will end up with an 88 through 93 or 94... maybe even a 95.
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Old 10-18-2018, 08:39 PM
 
Location: Riverside Ca
22,146 posts, read 33,639,819 times
Reputation: 35439
Quote:
Originally Posted by curiousgeorge5 View Post
@electrician4you: Thanks. I drove the successor transmission in a 'vette. A person shifted either 4 or 6 times. It was either gears 1 through 6, or 1 and 4 through 6. I thought the ratios in 1 through 4 were too close. Thinking about it now causes the term gimmick to come to mind.
Not really gimmicky. It’s basically a gear reduction drive bolted to where the tail shaft normally resides. I have one on my diesel and I tow 10k trailers and I never had a issue with my Gearvendors other than the cone clutch wearing. And there are rebuild kits out there for 3/350 I just didn’t have time to order one and rebuild it because I needed the truck running by a weekend.
I think the 4+3 could be shifted by letting off the gas or switching the solenoid with a switch. On my GV I have a switch on the shifter tha5 8 use to engage the OD. It is about 25% output reduction. So at 75 mph normally in regular 6th gear I’d on my ZF6 I would be turning about 2600 rpms when I engage the GV overdrive I drop down to about 2000 rpm.
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Old 10-20-2018, 05:21 PM
 
Location: Southwest
2,607 posts, read 2,334,698 times
Reputation: 1976
Quote:
Originally Posted by Electrician4you View Post
Not really gimmicky.


The 4+3 isn't gimmicky or the 6 speed that a person shifts 4 or 6 times, including first isn't gimmicky? I drove the 6 speed one but never the 4+3 'vette.


I like the 4+3 but not the 6 speed. Shifting 6 times, including 1st gear, is too much to me in a vehicle with a lot of torque like those mid to late 80s Corvettes.


Most Harley Davidson motorcycles made these days are 6 speed. That's 1 gear too many for me for that type of motorcycle. They could make 5th gear the overdrive gear. In the past there was a large motorcycle that was a 5 speed, with both 4th and 5th being overdrive gears. I think it was either a Victory or Kawasaki V-twin.
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