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Apr 13, 2005 | 09:38 AM

blockheadbob

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Junior User

Joined: May 2004

Posts: 66

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From: Idaho Panhandle

I have a 28 spline 9" rear end in a 78 F-150 and I was wondering if I can upgrade to a 31 spline, and what do I have to change? My ring and pinion are shot and there is quite a bit of wear on the splines.
Thanks,
Bob

Apr 13, 2005 | 09:44 AM

beartracks

Lead Driver

Joined: Nov 2000

Posts: 6,632

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From: Albuquerque

You will need axles and a "pumkin". You probably need bearings and seals anyway and the gears have to be set up by someone with experience. So that's not gonna be cheap unless you can canibalize another truck for the parts. If you can find a donor in good shape it would be much cheaper and just a matter of bolting in the parts.

Apr 13, 2005 | 02:16 PM

Mil1ion

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Joined: Jan 2008

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That's weird from what I thought, most trucks came with 31 spline.

Cars usually had the 28's.

Apr 13, 2005 | 02:23 PM

beartracks

Lead Driver

Joined: Nov 2000

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From: Albuquerque

Mine came with 31 but I've heard others have 28. Not sure what the criteria was.

Apr 13, 2005 | 02:55 PM

79schaefer

Tuned

Joined: Jul 2001

Posts: 439

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From: Erie, Pa

The "general" rule is that 2wd had 28 spline and 4wd had 31 spline. Like anything with these trucks tho, things are subject to change at any givin moment

Steve S.
To many to list

Apr 13, 2005 | 03:32 PM

savage066

Mountain Pass

Joined: Dec 2004

Posts: 123

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From: Maryland

i think that's correct...my '79 is 28 spline as well.

Apr 14, 2005 | 11:16 AM

blockheadbob

Thread Starter

Junior User

Joined: May 2004

Posts: 66

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From: Idaho Panhandle

Thanks for the input. My trucks rear end has probably been replaced at one time or another.

Bob

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Apr 15, 2005 | 12:28 PM

RTM

Cargo Master

Joined: Dec 2003

Posts: 2,735

Likes: 38

From: Sunny Florida

Most of the truck axles I have ever pulled have been 31 splines. I have pulled a couple van axles that had 28 spline axles but the last two vans had 31 spline axles. I have yet to pull a 28 spline axle from an F150, F100 yes.