hey just buying some parts for my rear end and am not around the truck at the moment, just wondering if 1977 ford f 150s came with 31 spline 9 in or 28 spline

 

It should have the 31's.

 

According to my decoder ring, it could have either. Is there still a tag on it? Post everything on the tag. Otherwise, pull an axle. Someone here posted a tip about the ends of the axles--31s look one way, 28s another. Wish I'd kept that info..... If I find it, I'll post.

 

I don't know if this is 100% accurate, and I just don't feel like pulling a wheel off my 31 spline axle out in the yard, but it SOUNDS right:

http://www.metropartsmarket.com/rearend/measure.html

 

It's a 150, so it came from the factory with 31's.

 

That is in-correct, an F150 could have 28 or 31 splines.

It could even have a Dana 44 (1977/79)!

The AXLE tag on the rear end is necessary to discover which one, without pulling an axle.

The spline count isn't on the tag, but when the tag is decoded, the rear axle parts list will be known, from that, the correct axle shaft part number will be known.

 

I've never came across a 150 4x4 that didn't have a 31 but I'm always the first to say "never say never" when it comes to Ford. How would a 44 end up under there ? Special order ?

 

For some reason, Ford used a few Dana 44 axles from 77 to 79. I saw a pickup once with a Dana 44 rear axle. Never figured out why they did it though.

 

Greetings: Anything to that link I posted about the way the ends of the axles look? OP does not say 4x2 or 4x4 btw....

 

Considering the available ratio's of 2.72-1, 2.75-1 and 3.00-1, the answer is: Fuel economy.

As far as the ends of the 9" axles being different, sorry, I have no clue.

 

You could get a 9" with similar ratios though.

 

True....but most 9's installed in trucks prior to 1980 were 3.25-1 and up (or down depending on how one looks at it).

 

Post number 4 here:

https://www.ford-trucks.com/forums/8...0-9-axles.html

Shows the above link to be inaccurate. The post shows 28 spline axles with the axle ends said to be 31 spline in the link. My faith in the internet is shattered and yet reaffirmed at the same time.