Doug Nash 4+3 swap?
Thread Starter
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
Doug Nash 4+3 swap?
My wife's 69 has 4.11s in it, and she likes the performance. However, for long trips she/we really want a 5th (overdrive) gear; better gas mileage and less wear and tear on the freshly rebuilt motor!
Cost of a "K" custom (5-speed) trans is a lot for a car that needs other things, is not raced, and sees less than 2000 miles a year. (Course it might see more mileage if it had an overdrive gear!)
I did a search on the 4+3 but didn't come up with much other than the overdrive is a PIA if not maintained (and what isn't!?). Does anyone have experience and info re swapping the Muncie to a 4+3 (Doug Nash) trans in a C3? Another consideration might be a ZF six-speed?? (I can get a new ZF for about 1/2 of what a new "K" might run me. The ZF is a gem of a trans, but I've not heard of anyone stuffing one in a C3. Intriguing, doancha think??
P.
Cost of a "K" custom (5-speed) trans is a lot for a car that needs other things, is not raced, and sees less than 2000 miles a year. (Course it might see more mileage if it had an overdrive gear!)
I did a search on the 4+3 but didn't come up with much other than the overdrive is a PIA if not maintained (and what isn't!?). Does anyone have experience and info re swapping the Muncie to a 4+3 (Doug Nash) trans in a C3? Another consideration might be a ZF six-speed?? (I can get a new ZF for about 1/2 of what a new "K" might run me. The ZF is a gem of a trans, but I've not heard of anyone stuffing one in a C3. Intriguing, doancha think??
P.
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Paul, Do yourself a big favor and put anything in BUT a 4 plus 3. I have had 2 of them in C4's and they were both seriously problematic. It is a flawed design and I guarantee you will be pulling hair out of your head. The Borg Warner T-10 isn't too bad but the OD unit (Doug Nash) just won't keep working. Rebuilt both of them twice and got a few miles out of them but the OD unit always acted up.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Depends on the year of the car. The THM-400 is best swapped out for the 200R4. Not certain about the THM-350, but I think the 700R4 is an easier swap for them. The '82 came with the 'first' 700R4's, so that's a 'no-brainer'.
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Paul, Do yourself a big favor and put anything in BUT a 4 plus 3. I have had 2 of them in C4's and they were both seriously problematic. It is a flawed design and I guarantee you will be pulling hair out of your head. The Borg Warner T-10 isn't too bad but the OD unit (Doug Nash) just won't keep working. Rebuilt both of them twice and got a few miles out of them but the OD unit always acted up.
I have to say... that my experience with the 4+3 reflects the same conclusion.
Thread Starter
Le Mans Master
Joined: Oct 2004
Posts: 6,314
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From: South-central Missouri
The consensus is to NIX the 4+3. The T56...? Hmmm... Have to look into that.
As for swapping to an auto - that's not a bad consideration, except we both agree that REAL Corvette/sports car lovers drive stick shifts!
(Besides, I don't want to also have to change diff gears as well.
)
P.
As for swapping to an auto - that's not a bad consideration, except we both agree that REAL Corvette/sports car lovers drive stick shifts!
(Besides, I don't want to also have to change diff gears as well.)P.
Race Director
Joined: Sep 2005
Posts: 18,640
Likes: 121
From: Farragut,TN
The consensus is to NIX the 4+3. The T56...? Hmmm... Have to look into that.
As for swapping to an auto - that's not a bad consideration, except we both agree that REAL Corvette/sports car lovers drive stick shifts! (Besides, I don't want to also have to change diff gears as well.)
P.
As for swapping to an auto - that's not a bad consideration, except we both agree that REAL Corvette/sports car lovers drive stick shifts!
(Besides, I don't want to also have to change diff gears as well.)P.
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From: Downtown Annapolis, MD. The Future is where we all have to live. Let's not screw it up.
St. Jude Donor '08-'09-'10-'11
Paul, Do yourself a big favor and put anything in BUT a 4 plus 3. I have had 2 of them in C4's and they were both seriously problematic. It is a flawed design and I guarantee you will be pulling hair out of your head. The Borg Warner T-10 isn't too bad but the OD unit (Doug Nash) just won't keep working. Rebuilt both of them twice and got a few miles out of them but the OD unit always acted up.
Having owned a 1988 A4 Z52 coupe and living on the C4 forum for 7 years, the guys with the 4+3s were generally having WAY more problems than any other group as a whole as far as transmissions go.
Just sayin'...
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
Don't overlook 1st gear when considering OD's. I've run a 3.55 rear ahead of a T-10 Ultra w/3.44 1st in my shark, and the resultant 12.2:1 1st gearing grew tiresome pretty quickly (subsequently sold it and went with a Muncie). So, IMHO any box with a 1st gear deeper than 3:1 is going to feel somewhat like granny-low with your 4.11. I typically like the gearing provided by 5-speed OD's, but ~10:1 being a fairly good rule of thumb for 1st gear in a street C3, if you really don't want to part with the 4.11 rear you might just be a good candidate for a T56...
1st - 2.66 x 4.11 = 10.93:1
2nd - 1.78 x 4.11 = 7.32:1
3rd - 1.30 x 4.11 = 5.34:1
4th - 1.00 x 4.11 = 4.11:1
5th - 0.74 x 4.11 = 3.04:1
6th - 0.50 x 4.11 = 2.06:1
...tho don't expect to pull 5th (not to mention 6th) to redline unless you've got big top-end power. Which ever way you go, hope that helps you think it thru.
TSW
1st - 2.66 x 4.11 = 10.93:1
2nd - 1.78 x 4.11 = 7.32:1
3rd - 1.30 x 4.11 = 5.34:1
4th - 1.00 x 4.11 = 4.11:1
5th - 0.74 x 4.11 = 3.04:1
6th - 0.50 x 4.11 = 2.06:1
...tho don't expect to pull 5th (not to mention 6th) to redline unless you've got big top-end power. Which ever way you go, hope that helps you think it thru.
TSW