14 bolt question

[496bb]

So, my 87 3/4 Burb (454/400) seems to have a bit of a leak from pinion seal I think. Also gotta fix a wheel cylinder. But, this diff cover has me a bit confused with the “76” marked on it. Is it a cover off an older truck? An axle swapped in? Will prob pop the cover off eventually to check what gears and setup is in there- but glovebox sticker indicates a 3.73. It’s a FF 14 bolt.

 

[nvrenuf]

The number could be anything, unlikely directly related to the model year. Some employees on production lines write on parts for various reasons, it could be an employee number signifying the part was inspected.

Pull the cover and look at the edge of the ring gear, it will have ratio and month / year info stamped in it.

 

[mcarlo86]

If it is a full float 14 bolt, then it is not original to that burb. 3/4 ton burbs of that vintage would have came with a 14 bolt semi float.

 

[496bb]

I think this FF is original. RPO shows 3.73 open. I found the same chalk marking, upside down, on the passenger frame rail. Pulled a wheel on the side I know I have a wheel cylinder leak. All looks the same as far as age and no indication this rear has been changed. I’ll be diving in to wheel cylinders and do brakes while I’m there. The pinion can just leak til I can have someone do a locker and replace pinion at the same time, as well as prob do 4.10. Pics for reference for y’all.

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[Craig 85]

2WD 454/TH400 Suburbans got the full float 14 bolts. I had an '88 and my friend had an 87. 4WD got the 14 bolt SF.

Also if you bypass the valve on the rear axle your rear brakes will work 100% better. That's a weight sensing proportioning valve. GM has had problems with them. I've removed them from 3 different trucks over the years.

 

[Strick]

14FF for sure. They're the best!

HS

 

[496bb]

2WD 454/TH400 Suburbans got the full float 14 bolts. I had an '88 and my friend had an 87. 4WD got the 14 bolt SF.

Also if you bypass the valve on the rear axle your rear brakes will work 100% better. That's a weight sensing proportioning valve. GM has had problems with them. I've removed them from 3 different trucks over the years.

Thanks! Can you give me some more specific instructions on how and parts needed to do this? I’m about to dive into full brake rebuilds on both sides due to a bad wheel cylinder. Might as well just go ahead and do it all since it’s kinda a pain to get the drum off anyway - I don’t know the shoe condition so new shoes/hardware/ wheel cylinders.

 

[Fat 454]

My '73 2wd C20 burb came with a FF 14bolt from the factory. I would think it was part of the 3/4 tonne trailering option package available on the SQBodies. Didn't think it was that unusual ??

 

[AuroraGirl]

My '73 2wd C20 burb came with a FF 14bolt from the factory. I would think it was part of the 3/4 tonne trailering option package available on the SQBodies. Didn't think it was that unusual ??

thats proper
the 1980s things had ot get lighter, cheaper, and if you didnt need a 14 bolt ff they didnt give you one. but gms definition of need kinda had a big * after it

 

[CountKrunk]

My 84 has a 14 bolt FF, c20. I guess it had the tow package?

 

[68post]

My 84 has a 14 bolt FF, c20. I guess it had the tow package?

If the C20 is the 3+3 in your sig, those use the ton frame also, (and they all came with the 14FF).

 

[Craig Nedrow]

I've been through this and did a writeup with pics and part #. Follow the link and start at post 22.

https://www.gmsquarebody.com/threads/1973-k20-350-to-454-swap.29840/page-2