Rear axle ratio
Thread Starter
|
Junior User
Joined: Oct 2004
Posts: 63
Likes: 0
From: Zanesville,Ohio
Rear axle ratio
My truck is a 1981 F150 302 AOD tranny.
What I am not sure of is the axle ratio.The code is 15 on the door jamb sticker,near as I can tell it is 3.25 but I am not sure,I tried looking for the sticker on the rear differential but could not find it.
When we ordered it new in 1981,we told the sales person that it would be used a lot on the highway.
The engine doesn't seem to be turning very fast at 65 mph as opposed to my other truck which has 4.10 gears it sounds as if the engine is going to come out from under the hood at 65mph,of course it doesn't have overdrive,just a 3 sp auto.
What I am not sure of is the axle ratio.The code is 15 on the door jamb sticker,near as I can tell it is 3.25 but I am not sure,I tried looking for the sticker on the rear differential but could not find it.
When we ordered it new in 1981,we told the sales person that it would be used a lot on the highway.
The engine doesn't seem to be turning very fast at 65 mph as opposed to my other truck which has 4.10 gears it sounds as if the engine is going to come out from under the hood at 65mph,of course it doesn't have overdrive,just a 3 sp auto.
Post Fiend
Joined: Nov 2001
Posts: 5,871
Likes: 0
From: Coutts Canada
3.25's, i've never heard of those being put in these trucks before, i've heard of them being put into cars a lot, but it could be a 3.00:1 too. Curious what rpm does it turn at 65 in direct drive (if you have the od 4 sp which i assume you do)?
Thread Starter
|
Junior User
Joined: Oct 2004
Posts: 63
Likes: 0
From: Zanesville,Ohio
I have the Automatic overdrive transmission,I have no idea what rpms the engine is turning at 65mph,I don't have a tach.
The truck pulls hills empty quite well at 65 mph although,the tranny will downshift out of overdrive to maintain speed especially if the hill is steep.
I don't pull a trailer or haul heavy loads but I recently pushed a Chevy Beretta up a steep hill,and the truck didn't seem to bog down at all.
My other truck has 4.10 ratio 31" tires,the engine sounds as if it is going to walk out from under the hood at 65mph,but the tranny isa 3sp automatic.
I have often wondered if this is hard on that particular engine for sustained highway driving?
The truck pulls hills empty quite well at 65 mph although,the tranny will downshift out of overdrive to maintain speed especially if the hill is steep.
I don't pull a trailer or haul heavy loads but I recently pushed a Chevy Beretta up a steep hill,and the truck didn't seem to bog down at all.
My other truck has 4.10 ratio 31" tires,the engine sounds as if it is going to walk out from under the hood at 65mph,but the tranny isa 3sp automatic.
I have often wondered if this is hard on that particular engine for sustained highway driving?
Posting Guru
Joined: Jan 2003
Posts: 1,388
Likes: 0
From: SE Texas
There's alot of those "quirky" gear ratios from 3.00 to 3.50 throughout the years. The trucks with a rearend closer to 3.00 will get stuck on wet grass with street tires, as they just spin one tire. The 4.10's are great for towing, and is ideal for 31" tires. At 65, you're turning about 2500-2600 RPMs. That sounds high compared to the overdrive, but it's not harmful. Peak Hp is usually around there or just a bit higher on the small V-8's. Like stated, jsut don't redline over 5K!!! If you don't have a tach, it's easy to add one. Even if you have an auto tranny, it's nice to see where it shifts and can indicate any shifting problems or erratic engine problems.
Post Fiend
Joined: Nov 2001
Posts: 5,871
Likes: 0
From: Coutts Canada
<<There's alot of those "quirky" gear ratios from 3.00 to 3.50 throughout the years>>
Thats true, not to mention alxes as well (long story short, needed to find soe 28 spline 9" for my 82 and they stoped in 82 with the truck 28 spline axles.)
Thats true, not to mention alxes as well (long story short, needed to find soe 28 spline 9" for my 82 and they stoped in 82 with the truck 28 spline axles.)
Trending Topics
More Turbo
Joined: Mar 2002
Posts: 508
Likes: 2
From: Easthampton, Ma.
#15 =3.25 Ratio 3750# capacity axle
Source of info: 1982 Ford Light Truck Service Manual (factory)
Steve G.
Source of info: 1982 Ford Light Truck Service Manual (factory)
Steve G.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Thread Starter
|
Junior User
Joined: Oct 2004
Posts: 63
Likes: 0
From: Zanesville,Ohio
Thanks to everyone for helping out,it is greatly appreciated!!!
Getting stuck is a major problem,as I sometimes pull into my yard which is on a slight incline,I put BF Goodrich All Terrain tires on my F-150 hoping to help eliminate tire spin in my yard on the incline (truck is 2wd) however,I still spin the tires and get stuck!
My other truck on the other hand (4.10) gears also 2wd has never spun a tire on the incline in my yard,never been stuck.I always thought it was do to the truck being slightly heavier than the F-150.
F-150 is a short bed,my other one is a long bed.
Never realized it is possibly due to the lower 4.10 ratio.
On other thing to,on two lane roads the truck with the 4.10 gears has almost unbelievable passing power,quite easy to "peg" the speedometer if I am not carefull in a passing situation.
It also seems to get better gas mileage in city driving as opposed to the 3.25 geared truck,but this reverses on the highway.
Thanks again!
Jeff
Getting stuck is a major problem,as I sometimes pull into my yard which is on a slight incline,I put BF Goodrich All Terrain tires on my F-150 hoping to help eliminate tire spin in my yard on the incline (truck is 2wd) however,I still spin the tires and get stuck!
My other truck on the other hand (4.10) gears also 2wd has never spun a tire on the incline in my yard,never been stuck.I always thought it was do to the truck being slightly heavier than the F-150.
F-150 is a short bed,my other one is a long bed.
Never realized it is possibly due to the lower 4.10 ratio.
On other thing to,on two lane roads the truck with the 4.10 gears has almost unbelievable passing power,quite easy to "peg" the speedometer if I am not carefull in a passing situation.
It also seems to get better gas mileage in city driving as opposed to the 3.25 geared truck,but this reverses on the highway.
Thanks again!
Jeff
Elder User
Joined: Oct 2004
Posts: 984
Likes: 0
From: Winnipeg, Manitoba
Originally Posted by mustange70
<<There's alot of those "quirky" gear ratios from 3.00 to 3.50 throughout the years>>
Thats true, not to mention alxes as well (long story short, needed to find soe 28 spline 9" for my 82 and they stoped in 82 with the truck 28 spline axles.)
Thats true, not to mention alxes as well (long story short, needed to find soe 28 spline 9" for my 82 and they stoped in 82 with the truck 28 spline axles.)
You'd be better off finding a 31 spline rear end and bolting it on from a similar/same year of truck.
FYI, pretty much any unit within 5 yrs either way should work. The 9 inch has been around for a long, long time.(could probably add a fair spread of years to the 5 yr mark actually) I bolted on a 79 31 spine rear-end onto my 69 with no troubles...direct swap, no special conversions needed. Also bolted on the front diff from the same donor truck, but had to get the wheels re-aligned to compensate for the longer wheelbase. Both diffs came off a 79 Bronco, and were bolted onto a 69 F100 with a full length box.
Post Fiend
Joined: Nov 2001
Posts: 5,871
Likes: 0
From: Coutts Canada
One has to be careful with the 28spline axles cause they had quite a few different length axles, and the car 9" rears have on axles at least 6" longer than the other as well. But I got the rear end for free and it has the 3.25 gears and a limited slip so i will run it till shes blows then replace it with a 31 spline one (have everything but the 31 spline limited slip and i need the 3.25 right away.
