Hey has anyone ever put lower gears in a C6 like the first gear is 10% lower and second is 5% lower and third stays stock. i was thinkin if i did that i could change my 33's with 36 or 38's keep my 3.54 ratio and then my rpms would b lower goin down the highway, what do yall think?

 

There are a couple of aftermarket kits with lower 1st and 2nd gear sets for the C6. One is from Ford Racing. I have also heard planetaries from an E4OD, which are lower on the first and second gear than the C6, can be put in the C6.

Stock C6 gearing is 2.47, 1.46, 1.00. Some say 2.46, 1.43, 1.00. Not sure which is correct but both are awefully close as not to matter in use.

E4OD gearing is 2.71, 1.54, 1.00 and 0.71 for the OD gear. The Ford Racing kit is, to the best of my memory, 2.74, 1.55, 1.00. Both pretty close.

What size engine are you running in this truck and how heavy is the truck? Also, what are you using the truck for?

Depending on the above information, running 36's or 38's with 3.54 gears, it doesn't matter what your 1st and 2nd gear ratios are, 3rd gear will effectively be like having overdrive and your trans will need to shift down to 2nd alot to get up hills because you dont have enough gear to pull 36's or 38's with 3.54's in 3rd gear. This will be especially bad if you intend to tow anything or live in a hilly area.

In my opinion, with the lower 1st and 2nd gears, though still better than stock gearing, with those big tires, you still won't have enough overall gearing to run those big tires with 3.54's and the truck be at all useful either off-road or for pulling anything.

You really need to get the truck axles geared right for the tire size and then if you need lower gearing in the first two gears, put the low gear sets in. Your gearing needs to be right in 3rd gear. Using 3rd as an 'overdrive' is really a miserable driving experience.

My truck came originallly with 3.55's and I have 33" tires on it. The truck is heavy (6500 lbs unloaded) and has a 351 & C6. Towing and climbing hills was a real disappointing experience.

I also thought of going to lower gears in the trans to help fix the problem, but the real problem wasn't first or second gear, it did alright there under most circumstances except starting on a hill. It was 3rd that needed the most help. The rpm's were too low in 3rd at normal driving speeds and the engine didn't have enough power. It was operating below it's usable powerband (rpm range). Driving in 3rd was like driving in overdrive all the time, no good for hills. I had to get a running start at hills and speed faster than I wanted to, just to bog out half way up and shift down to second, ending up going slower than I wanted to in the end.

I bit the bullet and swapped to 4.56 gears, which did take away from top speed on the freeway when unloaded, but gave me MUCH more power in all 3 gears, especially 3rd. I can now pull hills loaded in 3rd gear at a reasonable speed most of the time and when unloaded the truck doesn't bog at all, it just sings happily up the hill without losing much speed.

I spend alot more time with my right foot halfway down than before the gear change, where I spent ALOT of time with my foot all the way on the floor. Running at wide open throttle with the engine below the powerband uses alot more gas than running part throttle with the engine in the powerband.

I can tow at safe speeds in 3rd now instead of having to drive so fast to keep the engine revs high enough to have the power to overcome even very small hills. The truck feels like a completely different truck, much more enjoyable to drive, and my gas mileage went up under all circumstances when loaded and under most circumstances when unloaded except for driving fast on the freeway. I keep the speeds down on the freeway to save gas.

I could have gone to 4.10's with 33's and the gearing would have been fine for most uses, but since the truck is so heavy, the engine is small, and I use it to haul a camper and pull a trailer over mountains, I chose to go a little extra low on the ratio and it has worked out quite well for me. What works for you may be different.

You really first need to decide on what size tire you want to run, then gear the truck axles accordingly, then if you want more 1st and 2nd grunt, go with the lower gearsets in the tranny.

On the overdrive issue, bottom line is this: if you need an overdrive ratio, then you need a trans with an overdrive gear or an auxilliary overdrive unit, like a Gear Vendors. Gearing the axles rediculusly high for the tire size and trying to solve the lack of gearing with a lower first and second in the tranny will be nothing but a disappointment, in my opinion/experience with this issue.

 

thanks for the imput, i see the idea aint as good as i thought. thats why im glad this site is here to learn from other people's mistakes lol. ok this is my truck its a 75' F-250 with a 360 i wanna drive it some just for fun on the road yeah and to haul/tow too,aint much hills here in NW Ohio some mud roads and they can get pretty snowy with i like to drive in, yeah i got 33's should i just stay with them or 36's i dont get to mud to much any more no one lets me but i'll find something someday i would like to have some gas milage to drive and have enough to haul/tow 4000 to 10000 lbs i wanna get rid of the fe 360 they seem to b built good but i dont like the oiling system at all! i want a 351/400 or would a 302 built up alittle be fine cuz i got 2 of em one bord 40 over oh and everything for the fe is exspensive! heck they put 5.4's in the new HD fords why cant i make a 302 work? then i can get an AOD and build it some well enough of my blaberin what do u think?

 

If you swap out the 360 for another engine family, you'll have to change the transmission as well, as the bellhousing bolt patterns are different. The 360 isn't a bad engine and I would not swap it for a 302. The 302 isn't that great a truck motor, not enough low end torque and powerband is high in the rpm range. It likes to rev and it will want lower axle gears than what you have in your truck now.

I run a 302 in my Bronco with 31" tires and 3.50 gears and the gearing is not low enough. I live with it for now, but 3.73's would be better. I'm leaving it the way it is for now and later on when I go to 33" tires, I will swap the gears to 4.10's.

My Bronco is alot lighter than your F250. The 302 would have to work harder to move your truck, especially if you want to tow with it. With a 302 in an F250 with 33" tires that is going to be used for towing, I'd want 4.56 gears in it. That AOD tranny you talked about would help with gas mileage on the highway when running low gears in the axles.

If you want something from the Windsor engine family, you'd be better of with a 351W or even a 300 inline 6. If I was swapping it though, I'd go for a 460 or a 429 . A 390 would be a direct swap for the 360, but I don't know that it would really be worth the effort.

On the tire size issue, you're already at your gearing limits with 3.54's and 33's. I wouldn't go any bigger than that without changing the gears. Pulling power will only suffer by increasing the tire diameter.

Anyways, hope that gives you a few ideas to mull over .

 

Glen, you oughta get an award for the longest, most information-packed, useful, and accurate posts!

 

Glenn is good isn't he!

This is what I have listed for those transmissions:

E4OD= 2.72, 1.54, 1.00, 0.71
C6= 2.46, 1.46, 1.00

The Ford racing #M-7398-F kit is made from 4R100 parts and the ratios listed in the 2004 catalog are: 2.72 & 1.54:1, the 1:1 direct gear is unchanged of course. They list this as the same ratios from the previous kits made for E4OD parts. The older books list the same ratios for the E4OD kits #'s M-7398-B/C.

I am using E4OD parts in my C6 which means I will have the E4OD ratios. I did not buy a Ford kit. I got the internals from a cracked case E4OD for cheap.

 

Dont pass up a 390/428 if it is in drop in condition and priced right. Just getting rid of the cast iron intake and exhaust manifolds also shaves of a few hundred pounds.
A good HD truck engine is the 391 which is a FT version of the FE; heads and cam are designed for pulling and not top end as with the car engines. These were used in the F600 and similar. I would assume that the bellhousing and crank would accept a FE C6 and flexplate but DONT quote me on this.

For low end in partiular there is no substitute for inches.

I love the old 429 and presmog 460's BUT they require 92-93 octane as the cr was typically 10:1 and more. However with torque in the 480-500 range they would move a house.

 

Thanks for the kind words guys . I will make a note of the ratios and info you posted too Eric. Thanks for clearing that up. I'll be interested to find out how that tranny ratio swap with the E4OD planetaries works out for you once you get it all done. I don't have any plans to rebuild my C6 in the immediate future, but at some point it will need it and I'd like to do the upgrade then if it's worth the extra $300 for the Ford Racing kit.

 

ok so the 360 aint bad? i think fe's are good built i got that book from summit how to rebuild your big block ford i love the way the block is its like the old B RB mopar motors the block goes down past the crank but when i saw the oil passages !!!!!!!! what the heck were they thinkin the crank gets oiled last!!!! i like the 429 kinda hard to find but it is good,can u use the E40D behind that or do u need the electronics? they dont make OD's for the fe huh? i think i will just stick with the 33's for now well thanks for the info!!

 

Shade, check out www.transmissioncenter.net. They have adaptor kits to mate an AOD or GM TH700R4 to an FE engine. That site also has a low gear kit for the C6 as well as just about any transmission part you could possibly want for a C4 or C6.

 

i've been told you can switch the 1st and 2nd gear planetaries from the C6 with the E4OD. Supposedly they are interchangable. I'm gonna switch the first and second in my truck when i rebuild my C6 another 80,000 miles or so left. Ivan or Sheep Boy(Pro) should be able to tell you. it was one or both of them in a post about this same thing about 2 months ago.
-Aaron

 

Aaron, LMAO. Sheep Boy . Yeah I remember the sheep pictures up in Offroad recently. You guys are a Riot up there.

I'll check for the tranny post you referenced to see what they're opinions were on the swap. Thanks.