Hi all, monday the C6 is finally going in my 66 / 352 . I curently run 27 inch tires and a 3.54 rear ratio, im replacing a 3 speed overdrive so naturally im going to have to work with tire size and rear ratio to get the rpm's back down a bit, I tow a 181/2 foot Bass boat tow weight around 3,000 lbs fully loaded, Im looking at going to a 3.07 gear with 30 inch tires or a 2.74 gearset with 29 inch tires, will I be able to tow this rig ok ? I do have plans in the future to add headers ( I have dual flowmaster ) and a 4bl ( I have 500 holly ) to ad some low end tq, I was able to tow in overdrive fine with the old trany, but of course I didnt have it in overdrive in first gear at the boat ramp. The C6 is the end of updateing my running gear, I have power steering and power disk brakes, I love this truck!!!!!

the C6 is just finished being rebuilt and a shiftkit installed, I wish I had the money to put the close ratio gear set in but it will have to wate till another paycheck or two.lol. It is using a new stock stall tq converter.

If anyone had done this convertion I would sure like to hear of your experance on this.

Thanks as always - Jav

 

I run a FE C6, 3.00 rear P235 70R 15 setup in my 66. I pull a tandum axle car hauler loaded with no problems. I turn 2050 at 55 mph.

John

 

John, what do you run at 70 mph?
I am considering a 3.00 or a 2.75 to run in my rear, behind a 460/C6/Doug Nash overdrive.
I am thinking the 460 will have power to spare with a 2.75, yet get lower RPMs. I would like to get about 2100 at 70.

 

jowilker is that with a 352 ?

 

Naw. He runs a wimpy 390.
Nice looking truck, though!
Looks better than mine, that's for sure, but mine will out pull him.

Oh, Hi John, Didn't see you there! You up for grilled dead yard bird again? Come up my way and I'll fry you some!

 

I've posted this link before.....

http://www.parkercarburetion.com/Cal...RPM_TD_FDR.hta

Just enter info you have and it will auto solve for the unknown. Thus if you know tire dai and gear ratio you can find rpm ect.

44

 

Thanks I played around with the ratio's and it looks to get where I want I would need a 2.72 Gearset and 29 inch tires. my main question is this will the C6 and a 352 pull this gear set ? and will it work for towing ?
Looking back on it now maby I should have broke the bank and got the close ration gear set, that higher first gear would have helped at the ramp.

 

I have towed with a 2.75 rear. The high ratio makes take off more like a 240-6 that like the mighty FE that is in there.

John

 

those are some tall gears for towing. the 352 should be able to do it, depending on what cam and intake/exahust you have on it. It would have to be tuned to make it's power down low. I would stay away from the close ratio gears, those are exactly what you don't need for towing.

 

You are absolutely correct, but I don't tow everyday, I was doing it a lot for a spell, but haven't pulled anything with the truck in several months now.

My truck is built to run empty because that what it is used for 99% of the time.

John

 

All this info has me pondering my setup. I will use the truck to pull a 17'6" boat on a steel trailer I need to estimate the weight, although I didn't see this in the application for finding the ratio setup..

So how do I find out what rear gears I have at the moment ?

 

Question why not use the close ratio gear set I was told it changes only 1st & 2nd , to be like the C-4 trans has in there's. 3rd stay's the same . Or am i missing something. on it .
Don

 

Bob, Ford put thin metal tags on one of the bolts on the center chunk that has numbers on it, look for that.

There are a couple different methods for actual counting, and the one that I perfer will work for both the open and limited slip.

Start with the truck on level ground (pavement if available) mark the tire and roll it one complete reveloution. Either tape a piece of string to or have a friend count the number of revs. the driveshaft makes for the one tire rev.

Tire size can invluenance the outcome but this method will give you what your actual ratio is with all things included.

John

 

Thanks Jowilker, I seem to remember that last part from auto shop in high school. I'll check for a tag and recheck by 2nd method to see if it confirms it. Also I must be doing something wrong with the calculator, i tried the numbers you put up 55mph, 15 tire, 3.00 gear and got 3696 for rpm ???

Heck I dont have a tach on my truck (but would really like to add one) but not a bulky racing POC like I see on lots of trucks. Maybe I'lll start a new thread on where to get a stock looking tach and where to mount it.. LOL

 

You put 15" in as your tire diameter. So you be at 3696 RPMs if you took the tires off and were running on the rims! You need to use another calculator to find the full outside diameter of the tire you want to use. A 235/75R15 is almost 29" diameter, and puts you down to about 1900 RPMs.