Rear end welded?
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7th Gear
Joined: Dec 2018
Posts: 7
Likes: 0
Rear end welded?
I bought a great 1978 F-150 with 28k original miles but the rear-end is weird. I think someone welded the axles together because it struggles very badly in turns. I can hear one tire struggling and slipping. Do I need to replace the whole rear end or can I get a replacement diff? Can I go with used or should I get a new one? Where should I buy one?
Sorry for all the questions...
Thanks,
Lead Driver
Joined: Jun 2006
Posts: 5,653
Likes: 978
From: Near Yosemite CA
With the F150's they have the 9" rear-end, yes it is a drop out, what you have is the Old "Lincoln Locker" when guys would literally use a Lincoln welder to weld the spider gears for a cheap traction aid. Is your truck 2wd or 4wd? If 2wd, you can easily swap out to an open diff, count gear teeth to get gear ratio, also be sure to check spline count, most 2wd had 28 spline, 4wd were 31, although on a 45 yr old truck, anything is possible to be in there...
Logistics Pro
Joined: Oct 2006
Posts: 4,029
Likes: 891
From: East Central Ia
Depends on weight of vehicle. Look at your door jamb axel code or tag on axle. A limited slip will show up. I had 78 Bronco and wife a 2001 Blazer both with LS. We both had hard time backing into garage in a tight 90 degree.
More Turbo
Joined: Feb 2020
Posts: 633
Likes: 84
From: AL
Look up axle code and see if it’s a limited slip unit. With that amount of miles (unless it’s been rolled over) I would suspect it’s factory. If it’s been sitting the clutch plates could be stuck. I just swapped my factory 4x4 LS to a Detroit Truetrac. Haven’t ran it yet but read great things about them.
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Cargo Master
Joined: Nov 2007
Posts: 2,238
Likes: 475
With only 28K miles, unless it was a dedicated drag truck from almost new, I doubt someone welded the rear, it just sat around too much. More likely, it has a factory lsd and it's probably stuck with rust. I've had a few axles like that. The oil doesn't get slung around when they sit and everything above the oil line eventually rusts. Sometime if it's not too bad you can get it to break free by driving in slow tight circles and occasionally hitting the breaks kinda hard. You really should just pull it apart and see what's going on, instead of throwing parts at it.
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