My Axle

[78F250]

I found this plate on the 10 bolt rear axle. I think 3 31 is the gear ratio? What are the other numbers?

 

[LEB Ben]

This is a good one for Randy...he's usually on top of axle numbers. So here's a bump.

 

[Mil1ion]

Well D8TA means it was designed for a 78 ford light truck
suffix - GA,CGA, LC mean a 3.31:1 ratio


Is that 603899 ?

That means a dana.
I'll be back

 

[78F250]

So 3.31:1 is good for daily driving or towing?

 

[LEB Ben]

So 3.31:1 is good for daily driving or towing?

Means it's good for daily driving. Might be a little sluggish off the line, but the rpms will be low on the highway. The higher the gear (numerically lower) the lower the Revolutions Per Mile are going to be and vice versa.

 

[78F250]

My son, who I got it from, said it tops out around 60/65 mph. Seems strange with a 400 w/4bbl.

 

[LEB Ben]

My son, who I got it from, said it tops out around 60/65 mph. Seems strange with a 400 w/4bbl.

That does seem strange. I had a 351M in a Bronco with 3.55's literally running on 5 cylinders that could hit 73mph. So maybe it's time for a tune up or engine build. I know the relatively stock 400 I have in my Bronco now will hit 85-90 with some coaxing, but she does start running outta steam right around 75mph.

 

[Mil1ion]

The average ratio in Ford 4x4's was 3.54, or 3.73

My 4x2 has 2.75.

Most trailer specials have 3.00's or 3.25's

They try to match the gear ratio with the engine / transmission and use of the truck

 

[DNFXDLI]

Wouldn't the 3.73 and 4.10 be more suited for trailer towing?..my book shows those ratios with the highest towing capacity in both 2 and 4 wd.

 

[1985 Ford F-150]

Thats what Ive always figured more RPMs= more power to pull up hills and not have to gear down.

 

[dakonthemountain]

Means it's good for daily driving. Might be a little sluggish off the line, but the rpms will be low on the highway. The higher the gear (numerically lower) the lower the Revolutions Per Mile are going to be and vice versa.

Rep points to you man! That was the most understandable, short sweet explanation of gear ratios and what it means I've ever read!
Dak

 

[fatherdoug]

Means it's good for daily driving. Might be a little sluggish off the line, but the rpms will be low on the highway. The higher the gear (numerically lower) the lower the Revolutions Per Mile are going to be and vice versa.

Revolutions Per Mile? That's a damn big motor!

 

[LEB Ben]

Rep points to you man! That was the most understandable, short sweet explanation of gear ratios and what it means I've ever read!
Dak

Thanks...I try to adhere to the KISS (Keep It Simple Stupid) principal. You don't always need fancy terminology and whatnot when all you want is a quick answer.

Revolutions Per Mile? That's a damn big motor!

Yeah...I was off a tad with my bolding abilities, guess I shoulda just bolded MILE. They higher the gear you have, the less times your tire is going to rotate over the course of a mile, thusly engine rpm is lower...and the reverse is true with lower gears.

 

[Mil1ion]

IMO, the 3.73,4.10 is more for off road trucks.


A 3.25,3.50 with a 400 4bbl is fine to pull a 1200 lb trailer on gravel or paved hwy.

Not much passes me going uphill while I'm pulling my 4000 lb trailer in the mountains on paved road with my 429 and 2.75's

Only near the top of 4% grade will the C6 shift into second gear

 

[Alvin in AZ]

Only near the top of 4% grade will the C6 shift into second gear

There it is! ...the slush box allows for taller gears than a manual.

If you were to lean out the carburetor's full power circuit just-a-little
the C6 might not have to shift down at the top. BTDT, and it works.

IME 4.10 and 235/85-16E's (~31.5") are for hard workin' light trucks.

Butthead in AZ

 

[1985 Ford F-150]

Guess it depends on where ya live and what ya pull as to what gears work better for me 4.10s a 4 speed, and 33s are a pretty good combo for 6% grades or better with a trailer When we pulled the 72 home on a trailer with the 76 the grade was around 7 or 8 percent we figured and we had to drop all the way down to 2nd to get it up the hill. That truck had a pretty powerful 390 in it with 4.10s and 35s if it woulda had 33s or smaller tires it woulda done alot better. With the big tires on it the rpms and shift points were the same as the 85 that has 3.50s, 31s and a 4 speed.