I have a,69 250 C/S 390 C6 I don't haul things yet I just bought the truck rebuilt motor trans it has 374 rear gears at 65 she yelling help I need another gear !!!!!I wanted to swap the gears down the road I seen some put 325/328 what is the hghest gear that I could still haul a small camper maybe later a slide in camper I have a cam and a 500 cfm Holly that wants to run it's a toy really but it kills the fun factor beyond 65 mph .

 

 

A low number is a high ratio. A high number is a low ratio.

3.00:1 would be a high ratio. 4.11:1 would be a low ratio.

 

 

Actually I see all the way up to 7.17 now. Aftermarket has come a long ways for the low pinion dana 60. But 3.54 is max for low. And not worth the cost from 3.73. Maybe the best bang for buck would be an overdrive.

 

Consider larger rear tires to drop the rear end ratio numerically.

I.E. a 10% larger rear tire compared to stock is the equivalent of dropping your rear end ratio 3.73 * .90 = ~ 3.36.

If you were to go in that direction, I would make all 4 taller tires, due to tire rotations.

You will also have to correct your speedo gear in the tranny.

Michael

 

I have 9.50 x16.5 firestone don't think I could go bigger unless I changed rims to a 16 then the doors open up more , I just bought the tires transforce HT changing to bigger tires and a swap to 354 would be better , I heard of the gear vendor but that too much cash for me right now what other overdrive options are there for a C6 other than gear vendor ???

 

You wouldn't want to go from a 16.5 to a 16.- You need a 17" or 18" rim (and tire set).

 

Taller tires are the poor man's overdrive. That is why newer cars are using 17, 18, 20 inch tires. Your 3.73 gear is about perfect for a multi-use gear which allows for cruising and carrying a heavy load, such as the camper you want to put on. Get a set of Dodge 17 inch wheels. You can get them cheap from Craigslist or the JY. My son has a set on his 79 F-250 Lowboy. Your bump has the aerodynamics of a flat sheet of plywood straight up facing the wind. Your mileage can't improve much. Get rid of that gas sucking 500 cfm 2v Holley, and put on a 600 cfm 4v with vacuum secondaries with a dual exhaust. Save your money for the 4v carb and new 4v aluminum manifold instead of a minuscule gear change from 3.73 to 3.54 which will cost $1000+. You can get a 3.07 gear from a Dana 61 using a special Dana carrier, but it will cost $XXXX.

https://en.wikipedia.org/wiki/Dana_60

 

Why do you say that, you can get the same diameter tires for a 16" rim as you can for a 17 or 18" rim.

 

Like beer, bigger tires are the cause of and solution to most of life's problems.

 

9.50x16.5 tires are 30.3" in diameter and you can put 33" tires on the rear with a rim change. 16" rims and tires are your best bang for the buck. 17

 

Yes i understand that you can get the same tire HEIGHT in a different rim size, but if you are trying to go with taller tires then most of the time you want a taller rim too. Then the aspect ratio (the 70 or 80 number in the tire size) would be better for handling that way. Then the OP will not have tall but real skinny tires.

 

I have 35s on a 16" rim and they handle great. As a rule of thumb I like to have my tire diameter a minimum of twice the rim diameter, and for some odd reason the larger the rim diameter the more expensive the tire is even if they are the same diameter tire.

 

I should had looked into it before I bought the Firestone transforce there good tires but 16 with 33 " would had been better I agree too that a 17/18 tire is more expensive then a smaller wheel with a big diameter tire the tires that were on it when I bought it, Hercules Hercumile date code 1971 they had 80 percent rubber flat spots all over it sat for years in the guys driveway .
Thanks for all the info I learned something I had a wieght on my flexplate causing a vibration it made 65/70 feel bad put on the right flexplate it wasn't as bad I'm at 3k around 70 /75 2,500 be nice .