Much easier and cheaper to swap pumpkins. As far as the "best" gear ratio, it all depends on what you're doing with the truck and how you want it to perform.

 

You have to be careful what you buy, there is the 9" out of the cars that are 28 spline, 31 spline in the trucks, and a 28 spline 9.25" third out of the large boat anchor lincolns. You can find a pumpkin at the swap meet for $400 ish, or scour the junkyards for the ratio/spline count you want.

 

On the low gear kit of c-6 its great. 1st and second is working together nice but once you go to 3rd gear thats when you feel the load. so you set up final drive gear and axle ratio properly. The low gears really help out on getting it going then when in third you just cruise down highway. I run almost no stall in tranny for towing/working situation. When going from second to third under heavy load you have to run up rpms a little so it'll pull 3rd nice. I have a 40" hawg and 4.56 gear and c-6 lowgear tranny. Also the lowgear kit help tranny to handle more torque compared to stock set up. I did the good clutches and other cool kits. The arm that controls band in tranny is very important also on how quick it releases. factory link arm to band has letter like A or B or c. I was told everything from A to D letter is good. Tci has a aftermarket one that works great and have not had any problems with in yrs. This band needs to be adjusted properly. Has a external adjustment and need to btm out with inch lb torque wrench and back out 1 turn If I remember correctly been awhile since last check in book. Tranny cooler is nice also. Also on c-6 the roller/torrington bearings instead of flat shims help reduce friction and free's up energy used in tranny. I have done these little things in mine and work great. Just more stuff to think about when considering a new build. Also my 1 to 1 linkage carb builds torque right out of the btm rpm's to top end almost like fuelinjection.

 

Is that the wide-ratio planetary kit? That would be a different story - lowered 1st gear, slightly lowered 2nd gear, and 3rd gear is standard ratio - good for screaming out of the hole then taking your foot out of it and cruising

TCI does (or used to) make underdrive and overdrive planetary sets - where the ratio in every gear was either lowered or raised - not compromised like the wide-ratio planetary.

 

I've been looking,and it seems that the "tab" that should be on the rear-end...isnt there.
So now to know my teeth-count,I havta' pull it apart and count each one. This is just great. So,after I get the count,I need to figure out "which-way to go" in my Quest for less out of the hole,and more top-end. Here's a tid-bit that may be of some help... it's the stock rear-end for the '78 F100 Ranger 6 cyl. One look at the Springs and mounting hardware confirms this without a doubt. ...Anyone out there know what Rear-End Ratio's usually went into those Trucks ?...

 

Not so fast... check out this link and go towards the bottom of the page where it says "figuring gear ratio" in bold.

Tires, Gears, MPH and RPM Relationship Between

In short it's a formula you can use to calculate your gear ratio by jacking up the rearend and counting how many revolutions the driveshaft makes with one revolution of the rear wheels.

 

I mark the wheel, and turn the driveshaft 10 times to see how many times the tire moves. Much more easy to do the math.

 

Just gotta make sure you got a buddy turning the other wheel opposite of the one being counted - I tried this formula on my truck and realized the differential was goofing me up.

 

I usually chock the other side. I guess I should mentioned that... :-"

 

Oh you jack up one side so the other stays on the ground? Doesn't that change the gear ratio any because of the differential?

 

Ratios were anybodys guess. Half ton 2wd usually got 3.50 or numerically smaller, the 4WD you could occasionally find 4.10 gears. Jack up the rear end, chock one tire, mark the other tire in relation to the ground, turn the driveshaft 10 times, count how many times the tire turns. If it turns 3 and 1/2 times, you have 3.50 gears. If it turns 3 times exactly, its 3:1. Four and a half times, 4.56. If when you chock the tires, try to turn the driveshaft, and nothing happends, either the brakes are on, or you have a limited slip/locker in there. Usually the limited slip will make both tires turn the same way at once, but a locker act like an open diff unless you turn the driveshaft... It will make a clicking noise if you turn just one tire, and it is not locked up.

 

Its the under drive and If I remember its like 2.84 first gear been a long time since I done this and has worked flawlessly over the years. It's just one piece of the puzzle to makeing fuel mileage. Hole shots well and then just cruise in 3rd. helps get the weight moving and less energy used/air fuel going through engine, something to consider. Then work the rear axle with proper gear ratio.

 

Anyone ever get that website for the rebuilt gear vendors?

 

My 2 cents, I had a '86 motor home 460 ina 79 bronco, I took off the holley dual pump for a 750 Edelbrock electric choke. I did a tune up, K&N, 31s on 15x8 rims and a glass pack but mostly open exhaust. It was loud and I only went past 85mph once. I saw the gas gauge move as I was doing it.

The reason for the 750 carb: I was told by a guy who owned a 78 f350, that the 750 edlebrock a cam and headers will boost performance. And I had 1200$ in my pocket at the time so. I bought the carb, And I was able to get 15mpg @65mph thats not a joke. I couldn't believe it either. I was on the highway alot to get that.

My advice, get a block of wood, put it behind the gas pedal. Or invest in a tach, and dont have to much fun in it.