NEW GUY PLEASE HELP

[Craig Nedrow]

Welcome Barry. Went through my 14 ff, here is a link to the build: https://www.gmsquarebody.com/threads/1973-k20-350-to-454-swap.29840/
Rear end is around page two, lots of pics. Mine was an open diff, with 4.10 ratio. message me for any help i can give you. Nice truck BTW! and low miles, excellant!

 

[brushybarry]

hey thanks! I have not had a chance to pull my cover yet and see if any parts hit the ground. I just looked at your pics and my diff doesnt look like yours. mine is a 14 bolt but its round, it isnt offset like yours looks. ??? Your truck is awesome btw

 

[M00SE]

FIRST POST.
I recently bought an 84 k20. truck runs and drives like new but when cruising if you lay your foot on the gas as if to maintain speed it sounds like the rear end is about to come apart. PO said it has done this since he bought the truck in 08. My build sheet shows a G80 locking diff and GQ1 standard diff but says nothing of gear ratio. can yall tell me what I have and any ideas what kind of mess im fixing to be in trying to fix it. I thought i would just buy everything new and go through th rear end to be sure to get it right. thoughts?

Sorry to come into this late.... CHECK YOUR DRIVE LINE JOINTS. Easy and almost always the issues when I get another rig.

 

[brushybarry]

I crawled under the truck and couldnt feel any slop in the driveline. is there a better way to check?

 

[Bextreme04]

I crawled under the truck and couldnt feel any slop in the driveline. is there a better way to check?

Sometimes they will look fine and not have any rotational slop, but the grease has all dried out and they are rusty or dirty inside. If you dont feel any rotation slop and it doesn't move side-to-side either, you can remove the driveline and see if the joints rotate smoothly and the caps rotate smoothly. If they feel notchy or hard to rotate they probably need to be replaced. Honestly, they are so cheap that if you have never replaced them, you should probably just do it.

Also, a round cover means you have a 14 bolt semi-float axle. Not quite as strong or robust as the FF.

 

[brushybarry]

pulled the cover off. Didnt find any chunks of metal. just some rust and pitting. yall see anything crazy? im going to put it back together and change u joints to eliminate that. If thats not it then i guess it has to be the bearing on front of diff where yoke is ? pinion bearing/seal i guess its called? is 80w gear oil fine to fill her back up with?

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[brushybarry]

Taking a screwdriver I can jiggle this part here quite a bit should it move that much?

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[shiftpro]

Also, a round cover means you have a 14 bolt semi-float axle. Not quite as strong or robust as the FF.

Also know as a 9.5" 14 bolt.
The good one is the 10.5" 14 bolt.

You still have a better diff than a 10 or 12 bolt.

 

[brushybarry]

does anyone have a link to a video of how this rear end works? I dont know if that piece inside (what im guessing is) the locker is suppose to move like it does. i feel like a ******* asking over and over but i really am clueless lol. If the locker is FUBAR is it as simple as replacing it and back on the road? would this be the right part to completely replace it? OR should i rebuild the entire rear end? new gears and all since mine do have rust on them. thank you all for the help
https://www.jegs.com/i/JEGS/555/62836/10002/-1

 

[brushybarry]

Bextreme since I have a SF could my truck have a different gear ratio or was it still only available in this configuration with a 4.10 gear? may have found a complete rear end to swap

 

[Poppy 87]

Welcome Barry, my suspicion is worn pinion bearings. The description of when the noise occurs, coupled with being over a quart low on fluid would point me in the bearing direction. Nobody knows how long it was driven with a low fluid condition, but a quart low means those front bearings were not getting sufficient lubrication. Good luck

 

[BKING33]

If you are trying to verify your axle ratio, the tooth count is stamped on the ring gear. just rotate it till you find the numbers. the factory locker is a weak unit.
I would recommend a Detroit True Trac diff