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Specs on 1976 Axle?
- Thread starter pbets756
- Start date
I found out that it is a positive traction with a 3.70 gear ratio. Does anyone know how it will travel on the interstate with this ratio and automatic C4 transmission. Just wondering if it will be rapped up pretty tight doing like 70mph
Partially depends on what size tires you run. If you have G78-15 like OEM, will take more RPMs. I ran 9.00X16s with 411 gears on the road and it wasn’t running too awful high RPMs…to my notion, anyway.
If that helps any.
If that helps any.
- Joined
- Nov 3, 2003
- Messages
- 51,619
If you measure the actual diameter of the tire, we can use one of the online calculators to get what the RPMs will be at any given speed.
Aside from the tag on the differential, what is the axle code on your warranty plate riveted to the glove box door?
Just curious if they match.
Interesting tag. Usually there is an actual read out of the ratio. For example, a 3L70 spelled right out on the tag.
Is it there and I just can’t see it in the picture?Where did you get your information that it’s a 3.70?
Or is that A2, or perhaps the 5KA an actual axle code?
Aside from the tag on the differential, what is the axle code on your warranty plate riveted to the glove box door?
Just curious if they match.
Interesting tag. Usually there is an actual read out of the ratio. For example, a 3L70 spelled right out on the tag.
Is it there and I just can’t see it in the picture?Where did you get your information that it’s a 3.70?
Or is that A2, or perhaps the 5KA an actual axle code?
It may seem a little “buzzier” to you at 70, but it’s not as bad as you might think.
I can kinda see "4L11" on the lower left, and an unreadable "W" - "?" - "?" -"A2" as the axle code.
Then 5KA as First Week October, 1975.
I also see a non-factory fastening nut, and a painted carrier. I trust nothing at this point.
Considering a 3.70 ratio wasn't available in the Early Bronco, trusting nothing would be a good starting point.
While your axle may have been changed it's also possible that it wasn't. In that case what we're looking for is the part of the picture that is not legible in your original picture. Like mine shows a 3.50 Limited slip rear axle.
Looks like A2 on axle tag: 4.11 TracLok, 2 pinion
And A3 on warranty tag: 4.11 TracLok, 4 pinion
You can jack up one wheel and determine if it is locking,
jack up both wheels and count drive shaft revolutions per axle revolution and get close on gear ratio.
But after 1/2 a century, unless you open it up you will never know for sure.
Post #3,
A3 is 4.11 w/limited slip 2900 lb axle the J denotes power steering although before P/S was availible it denoted front LS
And A3 on warranty tag: 4.11 TracLok, 4 pinion
You can jack up one wheel and determine if it is locking,
jack up both wheels and count drive shaft revolutions per axle revolution and get close on gear ratio.
But after 1/2 a century, unless you open it up you will never know for sure.
Axle coding?
I looked a parts rig this afternoon. It is a '77 with an A3J axle code. I looked at the broncohio.com info. What I get is it may be a 4.11 with open diffs. Correct?
classicbroncos.com
A3 is 4.11 w/limited slip 2900 lb axle the J denotes power steering although before P/S was availible it denoted front LS
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Ok here is a better picture of the rear tag. I see it does say 4.11. the second picture is of the front differential tag which is easily readiable. I knew it was a positraction rear and it only has 52 thousand original miles and he would have told me if it was worked on. it looks like my planned trip next fall from Iowa to Yellowstone park with it is going to be a little noisy from engine rpm. thanks Paul
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- Nov 3, 2003
- Messages
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I often ran full freeway speeds with my 4.11’s and “32” inch tires. Probably about 31 inches actual, but I didn’t take measurements into account very often back then.
Nominal speeds were a bit lower in the 70’s through the 90’s than they are now, but I could run 70all day long, with spurts to 75-80 without any drama.
Probably spent much of its life running between 2800-3200 rpm for hours at a time. Engine was running fine at 175,000 miles.
But yes, fan noise, gear noise, reflected sounds through the sheet metal, tire noise, wind noise, and all of the above definitely made it a little less quiet than it would’ve been cruising in a Cadillac.
But no less fun!
A lot of my “performance upgrades“ over the years were geared around simply making it quieter. There’s a lot you can do, and even more nowadays. And it’s all worthwhile.
Nominal speeds were a bit lower in the 70’s through the 90’s than they are now, but I could run 70all day long, with spurts to 75-80 without any drama.
Probably spent much of its life running between 2800-3200 rpm for hours at a time. Engine was running fine at 175,000 miles.
But yes, fan noise, gear noise, reflected sounds through the sheet metal, tire noise, wind noise, and all of the above definitely made it a little less quiet than it would’ve been cruising in a Cadillac.
But no less fun!
A lot of my “performance upgrades“ over the years were geared around simply making it quieter. There’s a lot you can do, and even more nowadays. And it’s all worthwhile.
Broncobowsher
Total hack
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- Jun 4, 2002
- Messages
- 37,073
4.11 and 4.09 were a factory pair. No issues being slightly different.
Pairs nicely with 33" tires without overdrive.
A small block ford is completely happy spending its life at 3000 RPM. Makes a bit of noise, really doesn't hurt fuel economy so long as the fuel and ignition are working properly.
Pairs nicely with 33" tires without overdrive.
A small block ford is completely happy spending its life at 3000 RPM. Makes a bit of noise, really doesn't hurt fuel economy so long as the fuel and ignition are working properly.
You guys make me want to figure out my RPM at 70 with my stock C4, 3.50 gears and 31x10.50x15 tires. I don't have a tachometer but I'm curious enough that I might blue painters tape my timing light to the hood facing the windshield and go for a drive.
