Topic: Rear gear ratio with overdrive transmission
in Forum: C3 Driveline Components
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Yesterday Mark (manchestershark) and I spent about an hour or two on the phone talking about the overdrive transmission options. I could only speak from my personal experience with my 72 on how they act. He is considering going with a 700 trans and 3:08 gear ratio. I had no luck using the 3:08 gears in mine as the lugging was to severe and I ended up going with 4:11 gears. Mark found in his NCRS information that a few years of vettes (early 80's) used the 2:70 rears with overdrive trans.
So now Mark and I have a few questions about your setups:
1. What ratio's are you using with your overdrive transmissions either the 700 or the 200r4.
2. Are you having any lugging issues.
3. Have you gone to a lockup switch to control your lockup speed.
4. What stall convertor are you using
5. What TV system did you use
Was the cost of your conversion worth the money you spent to do the swap.
Looking forward to seeing the answers to these questions as well as any additional comments or information you want to add to this.
Thanks
Rodney
So now Mark and I have a few questions about your setups:
1. What ratio's are you using with your overdrive transmissions either the 700 or the 200r4.
2. Are you having any lugging issues.
3. Have you gone to a lockup switch to control your lockup speed.
4. What stall convertor are you using
5. What TV system did you use
Was the cost of your conversion worth the money you spent to do the swap.
Looking forward to seeing the answers to these questions as well as any additional comments or information you want to add to this.
Thanks
Rodney
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My '82 when it was stock had the 700R4 with a 2.72 rear. The problem was the converter would lock-up at 40mph and if you started up a hill it would really start chugging. I would have to shift to 3rd of give it gas so it would down shift. But it would go into lock-up as soon as the load came off.
After I put the new engine (ZZ4) in it my trans guy set it up so it would only lock-up when in 4th gear. With the more powerfull engine you can't even notice when it goes into lock-up. I changed the rear to 3.55 gears. I think you can get by fine with 3.08 gears as long as your engine is strong and the lock-up only comes on when you're in 4th gear. The TV cable set up is VERY important on the 700R4 trans, you can do some real damage very quickly if it's not set right.
I'm not a trans expert by any means, but this is my 2 cents worth.
Dave
Lifetime Member #116
Dave's '82 
Does anyone know if a Gear Vendors Overdrive will fit behind a THM400 in a C3? I know the units are pricey but seems like a way of keeping the excellent and simple reliability of the THM400 and benefiting from 3 extra overdrive gears.
2012101154624r.jpg)
Build Date: May 7, 1975. 383 w/267 RWHP/310 RWTQ
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Rochester, NY - USA
Joined: 6/12/2012
Posts: 95
Vette(s): 1980 L- 82 fully restored and upgraded.
If you do not have a fuel management system (ie) fuel injection... YOU CAN NOT run 2.70 or 3.08 rear gears . The car will lug and chug like a patient with TB ... And the reason is the carb is beyond its ability to supply the engine with and air fuel mixture to compensate for low rpm and high load your under.
|UPDATED|2/10/2013 4:55:24 PM (AZT)|/UPDATED|
|UPDATED|2/10/2013 4:55:24 PM (AZT)|/UPDATED|
1980 , ZZ430 , 3.92 rear , 700R4 2400 stall NEW EZ EFI
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20218
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Case75 said: Does anyone know if a Gear Vendors Overdrive will fit behind a THM400 in a C3? I know the units are pricey but seems like a way of keeping the excellent and simple reliability of the THM400 and benefiting from 3 extra overdrive gears.
It's a bit off-topic, but it WILL fit...IF you don't mind cutting up the body(trans tunnel), and modifying the crossmember and driveshaft.....
Rosen put Hone overdrives in several Motion cars way back when....in the end, it wasn't really worth the trouble.
Joel Adams
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Adams' Apple said:
It's a bit off-topic, but it WILL fit...IF you don't mind cutting up the body(trans tunnel), and modifying the crossmember and driveshaft.....
Rosen put Hone overdrives in several Motion cars way back when....in the end, it wasn't really worth the trouble.
Case75 said: Does anyone know if a Gear Vendors Overdrive will fit behind a THM400 in a C3? I know the units are pricey but seems like a way of keeping the excellent and simple reliability of the THM400 and benefiting from 3 extra overdrive gears.
It's a bit off-topic, but it WILL fit...IF you don't mind cutting up the body(trans tunnel), and modifying the crossmember and driveshaft.....
Rosen put Hone overdrives in several Motion cars way back when....in the end, it wasn't really worth the trouble.
Thanks Adam. I realize it's a bit off topic but I had been looking at these on the web and was curious. Apologies to the OP.
Build Date: May 7, 1975. 383 w/267 RWHP/310 RWTQ
in Forum: C3 Driveline Components
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