rear end ratio
- Thread starter Russ
- Start date
A
Anonymous
Guest
Most folks feel that there isn't any such combination with the 200 and a C4. 
Seriously!
Seriously!
FastRonald
Well-known member
8) I'd use a 3.25 gear set
In Aussie, log head 3.3's in much 3000 pound Falcons never got any thing much steeper than a 3.23:1 diff. Tires in these cars were always about 25" tall unloaded. Some sedans later in the seventies would go to 2.92:1 if it was in a 2500 pound car with 23 " tall tires.
If it was a Falcon pickup (ute) it would get 3.5:1 gears.
On the stock 200, a C4 is a good transmission system. The engine has good low-end torque, and although its no 302, its quite okay with a 3.25, 3.23, or 3.20 ratio.
If you wan't a quick get-away, then the lock-up clutch C5, which uses a truck C4-style bell housing, is a better option, but you should always stick with the 3.25-3.20 gears.
On the open road at 60 mph, there is about 2700 rpm of engine revs. Any auto with a lower geared ratio like 3.5:1 or less, and it will scream, any taller, and it will be Captian Lethargic.
1980's Foxes could hack 2.79:1 gears or even taller because the lock-up C5 clutch allowed the trans to slip enough at low rpm to gain some forward motion.
That should help you.
(If you want a rapid take off, follow Al's lead. Get a T5 Mustang gearbox and 3.5:1 gears. Then you get both a tall overdrive 5 th, and a stump-pulling first!)
If it was a Falcon pickup (ute) it would get 3.5:1 gears.
On the stock 200, a C4 is a good transmission system. The engine has good low-end torque, and although its no 302, its quite okay with a 3.25, 3.23, or 3.20 ratio.
If you wan't a quick get-away, then the lock-up clutch C5, which uses a truck C4-style bell housing, is a better option, but you should always stick with the 3.25-3.20 gears.
On the open road at 60 mph, there is about 2700 rpm of engine revs. Any auto with a lower geared ratio like 3.5:1 or less, and it will scream, any taller, and it will be Captian Lethargic.
1980's Foxes could hack 2.79:1 gears or even taller because the lock-up C5 clutch allowed the trans to slip enough at low rpm to gain some forward motion.
That should help you.
(If you want a rapid take off, follow Al's lead. Get a T5 Mustang gearbox and 3.5:1 gears. Then you get both a tall overdrive 5 th, and a stump-pulling first!)
A
Anonymous
Guest
I'm running 3.20 gears....60 mph is right around 3000 rpms (forgot tire size, maybe 205 60R/14??) C-4 auto tranny.
Was thinking about swapping to a 3:50 gearset....
Later,
Doug
Was thinking about swapping to a 3:50 gearset....
Later,
Doug
A
Anonymous
Guest
With 215/60 15's, a 2.80 rear end ( :rolflmao: ) and a C4, I run around 2300 rpm's at 60 but no quick take offs are possible.
I may change over to 3.20 this summer but that will have to wait.
I may change over to 3.20 this summer but that will have to wait.
With autos, its rob Peter, give to Paul for quick getaway and quiet crusing. Thats why auto-punters will look to bolt on over drives for C4, or whole Chevy THM 200 R4's and AOD's swaps from hear on in.
Its too much to ask a ratio spread on 2.4:1 or so to meet the needs of 2004 traffic. Even wide ratio options can't cover the gearing 'gulf' that a 3-speeder has.
Split the difference, and go 3.5:1 if its a real hot I6, and stick with 3.2's otherwise. 3.89:1 sound like fun, but unless your running monster tires, your car will be screamiong more than it has to. But its all down to what you want. A 3.89 gearset sounds pretty good for something where the cops rat you out if you go over 60 mph.
At 80 mph, a 25" tireed 200 with 3,89:1 would be doing around 4250 rpm or so. Not nice.
Its too much to ask a ratio spread on 2.4:1 or so to meet the needs of 2004 traffic. Even wide ratio options can't cover the gearing 'gulf' that a 3-speeder has.
Split the difference, and go 3.5:1 if its a real hot I6, and stick with 3.2's otherwise. 3.89:1 sound like fun, but unless your running monster tires, your car will be screamiong more than it has to. But its all down to what you want. A 3.89 gearset sounds pretty good for something where the cops rat you out if you go over 60 mph.
At 80 mph, a 25" tireed 200 with 3,89:1 would be doing around 4250 rpm or so. Not nice.
A
Anonymous
Guest
My 66 I-6 has a3.03 to a 3.55 8 inch. Very fast take offs at the lights. 
Just took a trip from Houston to El Paso non-stop and registered almost 800 miles. I thought I was getting around 24 miles to the gallon at 80+ miles per hour and 3200 RPM. I had to check the mileage on the map and it's only 724 miles. It appears the 205/14's and the gearing in the rear change the mileage to around an exta ten percent. This makes actual mpg 22, unsure how the speedo is affected as it appears driving through traffic and those "Check your speed" meters on the highway closely reflect actual MPH. Never the less the 80 mph and 3300 is a good reflection with a 3.55 and the larger tires. Trip home was at 90 mph average, 3500rpm, and 20 mpg. This is pretty acurate as the trip time with 3 stops was just over 9 hours for the 760 miles measured by map.
I have A T-5 I bought for $75 but still need s a rebuild on the 3rd gear. I look forward to the overdrive
Just took a trip from Houston to El Paso non-stop and registered almost 800 miles. I thought I was getting around 24 miles to the gallon at 80+ miles per hour and 3200 RPM. I had to check the mileage on the map and it's only 724 miles. It appears the 205/14's and the gearing in the rear change the mileage to around an exta ten percent. This makes actual mpg 22, unsure how the speedo is affected as it appears driving through traffic and those "Check your speed" meters on the highway closely reflect actual MPH. Never the less the 80 mph and 3300 is a good reflection with a 3.55 and the larger tires. Trip home was at 90 mph average, 3500rpm, and 20 mpg. This is pretty acurate as the trip time with 3 stops was just over 9 hours for the 760 miles measured by map.I have A T-5 I bought for $75 but still need s a rebuild on the 3rd gear. I look forward to the overdrive
x21
Well-known member
Since my 68's C-4 auto had no O/D gear, I felt the stock 2.83 gearing was good with my stock 14" wheels, sporting 205/70 tires. This is a decent combo for more of a highway driver without O/D. If you never really intend on trying to hit 70+ mph for extended periods of time, you can try one of the lower gearings for better acceleration.
A
Anonymous
Guest
Well, as long as opinions are like...well, you know....here's mine;
my Fairmont has the 2.79 rear gear behind the C4, in a wagon. It's always had a great launch because of the torque converter, but falls on it's face at hiway speeds (mostly because of the EGR pollution controls - much better when disconnected), which are usually 80+MPH out here in the West. It does get good MPG on the highway, but the around-towm MPG suffers from the tall gears. If you mostly do in-town, under 50-MPH driving, something around 3.03 would be a good choice. This would give great start-launches and let the tranny slip into high gear earlier (like 28 MPH), which will contribute to better MPG.
MPG is like wisdom: you get it in little bits, here and there.
Another tip: don't go too far with initial spark advance. Retrading it a bit will 'move the heat' further down into the cylinder, which presses longer on the top of the piston. There is a slight loss of low-speed power, but it becomes MORE power above 1500 RPM, then less power again above 3000 RPM. But, with most cars, the 3000 RPM is a rarity in city traffic.
This is one of the algorithms used in fuel-injected engines to improve the MPG: less spark advance under light loads + leaning out the mix.
my Fairmont has the 2.79 rear gear behind the C4, in a wagon. It's always had a great launch because of the torque converter, but falls on it's face at hiway speeds (mostly because of the EGR pollution controls - much better when disconnected), which are usually 80+MPH out here in the West. It does get good MPG on the highway, but the around-towm MPG suffers from the tall gears. If you mostly do in-town, under 50-MPH driving, something around 3.03 would be a good choice. This would give great start-launches and let the tranny slip into high gear earlier (like 28 MPH), which will contribute to better MPG.
MPG is like wisdom: you get it in little bits, here and there.
Another tip: don't go too far with initial spark advance. Retrading it a bit will 'move the heat' further down into the cylinder, which presses longer on the top of the piston. There is a slight loss of low-speed power, but it becomes MORE power above 1500 RPM, then less power again above 3000 RPM. But, with most cars, the 3000 RPM is a rarity in city traffic.
This is one of the algorithms used in fuel-injected engines to improve the MPG: less spark advance under light loads + leaning out the mix.
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