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I have a 78 F150 that im slowly building up for some truck pulling. I alo want to still be able to drive it on the street. I know this is a hard combo to pull off. It has 3.50 gears in it now and firts gear is just too high even in low 4wd. Who makes a lower gear set for these transmissions? If i had a lower 1st gear then I could still maintain a decient rear ratio to drive it on the road. The transmission right now has a B&M compition style shift kit, adjustable modualtor valve and a 2300 stall convertor. The least expensive way to gear it down would be the best.
 

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I just rebuilt my C6 and bought the lower gear set from Jay at Broader Performance, he was very helpful and has good parts.
 

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Why not just lower the axle ratio's & put a 4 speed in ? Try as you might the C6 won't hold up forever pulling, and it's always a expensive explosion + you are always at a disadvantage with TC slipage as well.
 

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I emailed Frank he said the aftermarket low gear set dont hold upwell to a high torque situtation such as pulling. Im looking to get a set of 4.10s for the truck. I have a BW T18 transmission and a flywheel sitting around. Im just kind of relunctant to put it in because it would have my garage tied up for awhile and the transmission i have is for a divorced transfer case or 2wd truck. Anyone want to trade for a married transfer case style? I whould have to do alot of changing around. But I am sure the 4 speed would be a better option. A few years ago i had a brand new 12" clutch flywheel Im thinking out of a med duty truck had it zero balanced and sold it for $100 like a dummy lol. An auto eats up quit abit of power.
 

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If it helps any, pulling in low gear all the time with an auto trans. the planetary gears turn "Ford Blue"!
 

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If I was ever to get into a C6 seriously would fully rollerize it. Did a drag car wit ha c4 then a powerglide then a rollerized C6 it blew the doors off either of the other setups.
 

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look into the 4r100 low gear planetaires.6 pinion all steel planetaries.ford used them in the f250/350 diesels.never have seen one fail.if it did.it was due to lack of lubrication from some other issue....
 

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Discussion Starter #13
What year trucks should i look for to find the 4r100 transmission? How many other parts from one would i have to swap over?
 

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Why not just lower the axle ratio's & put a 4 speed in ? Try as you might the C6 won't hold up forever pulling, and it's always a expensive explosion + you are always at a disadvantage with TC slipage as well.
What are you pulling?

I DO NOT RECOMMEND ANY OF THE FOLLOWING PRACTICES:

I've grossed over 68,000 lbs several times dragging trailers with a 360/C6 combo in a 68 F100, and I had one pull that was around 84,000 (long time ago, not permitted, but "it had to go"). As long as you have a reasonably hard surface and enough air in the tires, you can drag it: it's like the F150 dragging a cut of railroad cars or the pickup pulling a 747: if you have an iota of engineering sense, you can do things that impress the heck out of folks not quite so clever. My moves weren't stunts: they were 30-35 miles for the shortest one, about 280 miles for the longest.

A more typical example was 45k for almost 400 miles at 75+ mph -- and God only knows how much gas, but it was a loooooooot, even with prices under 40 cents per gallon!

JR78-15; can't remember the ply rating, but it was the most I could find; 90 psi in the fronts and more than 110 psi in the rears. 3:00 OE gears.

I DO NOT RECOMMEND ANY OF THE FOREGOING PRACTICES: STAY WITHIN THE PUBLISHED LIMITS FOR YOUR VEHICLE, AND LAWFUL LOADING PRACTICES AND LIMITS, WHICHEVER PRESCRIBES THE LOWER COMBINATION WEIGHT.

Also: it's better to let the fluid coupling slip (as it was designed to do) than to slip the clutch (which was not designed for extended slippage). Who wants to be constantly crawling under their vehicle to replace discs? If the load doesn't move, there's a reason: solve that problem before you break something. If the load does move, the fluid coupling of the automatic is always going to be easier on axles, u-joints, etc.
 

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I have a 78 F150 that im slowly building up for some truck pulling. I alo want to still be able to drive it on the street. I know this is a hard combo to pull off. It has 3.50 gears in it now and firts gear is just too high even in low 4wd. Who makes a lower gear set for these transmissions? If i had a lower 1st gear then I could still maintain a decient rear ratio to drive it on the road. The transmission right now has a B&M compition style shift kit, adjustable modualtor valve and a 2300 stall convertor. The least expensive way to gear it down would be the best.
Install a 6R80 instead of the C6.
The base C6 ratios are 2.46, 1.46 and 1.00; the wide ratio gearset gives you ratios of 2.72, 1.54 and 1.00.
The 6R80 is stronger than the C6, and it comes with 4.17, 2.34, 1.52, 1.14, 0.87, and 0.69:1 ratios.
Additionally, the 6R80 is very much more efficient than the C6, so more energy from the input reaches the output.
And, the 6R80 will let you run a lockup converter, and have cooler trans fluid temps, and get better fuel economy on the road.
 
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