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Clunking from the read end

Winter Hill Gang

Winter Hill Gang

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Live from St. Mary's
So I'm driving my truck into town this weekend, and I forgot something at the home, so I go to pull a quick U-turn. The noise that comes from the ass-end of the truck sends shivers up my spine. A massive clunking noise. Now I'm all worried that something snapped. So I park it on the side of the road and drop underneath to take a look but cannot find anything visisble. So I take off and drive it home. no noise until I go to turn into my driveway. It seems the clunking only happens when I turn. Anyone have any ideas? I was thinking the side gears are perhaps binding.
 
i would guess its a 10 bolt and that you probably mashed your spider gears, but im no expert.
 
Ok, I just finished reading some very informative threads on rear ends 14bff and the 14SF. Now I am assuming this truck has a 10 bolt in it as well. its an '85 k5 jimmy. it will however not be doing much for mudding, climbing anything like that. Just driving in the winter more or less. Would it be cheaper for me to replace the spider gears in the 10b, and just be on my way, or should I seriously consider replacing the whole rear end. And I DO NOT have unlimited funds for this thing, so cheaper is usually better. ;)
 
toss up

You can probably find a 14 bolt for nearly the same price as a 10 bolt,maybe even less..10 bolts fail quite often,and are in high demand at junkyards..while the 14 bolt sf and FF dont give much touble,and only 4x4 enthusiasts buy them mostly..not too many of them croak in normal street use..They aren't any more difficult to install than another 10 bolt,if you get the right one(not a dually or cab and chassis or van one),only a u-joint might be needed,and some E-brake cable modifications..

The 10 bolts often wear out the differential case where the axle side gears ride..my 81 G10 van had that problem..after a 1200 mile ride to Nashville TN,I heard a clunking noise around corners,and while coasting at 15 mph or so--I assumed it was a u-joint going out,so I bought 2 and kept them with me,in case one failed on the way home..

I drove the van only sparingly the next 2 years locally,never bothered to put the u-joints in until the noise got worse..after I did,it was still there..then I pulled the diff cover off,and discovered the wear in the case ,allowing the side gear to flop around..everything else inside (spiders,ring and pinion,bearings) were mint--it was a six cylinder automatic,so it wasn't like the rear end saw lots of tourque or abuse..

I put another 10 bolt in,I couldn't find a 12 bolt from an older van--and I made the mistake of using a 2.73 ratio,rather than a 3.08 or higher like I should have..of course I found a 3.42 ratio one a week later at the same boneyard!..its a real dog with those "highway" gears..but I got the rear end free from a friend who was junking a van,so the price was right..

I'd say go for the upgrade to a 14 bolt..the full floater's(FF) are much stronger than the Semi-floaters (SF),but I overloaded my K20 with an SF many times with way more weight than it was ever designed for,and it never gave me a lick of trouble.. by the time you fix or replace a 10 bolt,you've already spent as much as the 14 bolt will cost you most likely--and its still a 10 bolt! :doah: :crazy:
 
Cheaper is better, eh? Stick with the 10 bolt. If you aren't doing anything other than driving in the winter, get a stock open carrier, stick it in the 10 bolt and call it a day. You don't need a 14 bolt FF to drive on the street. That's overkill. Besides, that'll save the 14 bolt for a guy who climbs rocks and needs it. Price comparo:

10 bolt fix, worst case :
ring and pinion : $140
Master install kit : $100
Open case : $140
Total : $380 plus install

14 bolt FF conversion :
14 bolt axle : $150 to $400 for one in good shape
Custom u-bolts for rear : $80
Conversion u-joint : $27
Front hubs and backing plates to go 8 lug : $200 or more
8-lug wheels : Vary...say $250
16" tires because 16" wheels fit without grinding, modifying : $400
Total : $1,100....with the variances at their lowest. This is assuming there is NOTHING wrong with the 14 bolt in the first place. Add brakes, bearings etc. as they come along. 14 Bolt FF drums are almost $100 each....

Get my point? Just fix the 10 bolt.
 
I guess I should mention it has 35" x 12.5 tires. if that makes any difference at all. I'm going to start calling the local yards this afternoon. just to see what I can come up with.

thanks for all of the information so far. You guys have been a ton of help.
 
You're gonna need to torch the spring perches off and re-weld some new ones to the correct width on your truck. Make sure the gear ratio is the same as the front, if it's different you are gonna tear the t-case in half. I'm not sure about the shock mounts. See if they are on the same sides as the 10 bolt coming off. You're probably still gonna need new u-bolts for the larger tubes, and possibly spring plates for them. Not sure if they parking brake cables will work either. Might want to search for something on a 14 bolt SF swap and if you can't find anything, post up a question.
 
My 90 GMC suburban with a 10 bolt on 35's did the exact same thing around corners and while making U-turns, and about 4 days later it got to the point that it would "Hang Up" and then free itself every once in a while.

I made the mistake of driving it out to a local Differential shop,(key word being DROVE it out) and it came back on a tow truck with a busted ring and pinion and a busted sunshell in the transmission, I'm having to take the shop owner to small claims court for damages he refuses to fix.


And before i knew any better i paid 400 bucks for another 10 bolt so i could get myself back to work. If i only knew then what i know now i would have gotten the 14bolt ff.

I want to go to 39.5's now that i have an 8" suspension lift, but im scared to put anything bigger than 35's on this 10 bolt.
 
Its cheaper to just become a member here and then buy a used carrier for like $20. Hell, I've seen guys on here give away 10bolts but you need to be a member to reap the benifits. For example I've got 2 sets of stock 10bolts, and 2 sets of 10/12s sitting behind the shop that need a home but I'm a little ways from you. I don't think I'd pay alot for a 14sf unless it matched your front and was ready (brakes, seals, perches) to bolt in.
 
Is there any way to tell what gearing is in the truck other than counting the teeth themselves. I've looked on the OE list and the gearing code is not listed. it does say G80 unfortunately. :(
 
Another question, if I went with a 14bff, and it bolts right up, other than the u-bolt and conversion-joint, the 8 lug wheels would be the only other thing to get right? could they still be 15" wheels or do I have to go 16"?
 
Sounds like your gov-lock is busted.

You might be best off (for cheap) to pull the cover and see what it looks like inside. Mine used to stay locked and going around corners was not real pretty. Anyways, buddy was poking around in there, broke part of the latching mechanism, and it was fine for years (until I sold it) afterwards.

It would be an open diff, but if not doing any serious off-road stuff, 4wd alone might be enough for you.
 
dyeager535 said:
Sounds like your gov-lock is busted.

You might be best off (for cheap) to pull the cover and see what it looks like inside. Mine used to stay locked and going around corners was not real pretty. Anyways, buddy was poking around in there, broke part of the latching mechanism, and it was fine for years (until I sold it) afterwards.

It would be an open diff, but if not doing any serious off-road stuff, 4wd alone might be enough for you.
Click to expand...


so what you are saying is technically all I have to do is a little bit of 'poking'. I pride myself is being great at the exact activity. :D
On a more serious note, if I bugger up the latching mechanism, purposely of course, it will simply turn it into a non-posi rear end, or open-diff. Am I on the right track here?
 
Probably...but you're still going to be "modifying" a POS carrier in the first place. I'd just get an open carrier and stab it in there. Less pain and you can actually rebuild it much later, where as a gov-loc, you're screwed. The locking is what made it goof up. Throttle, large tires and asphalt are not good for a gov-lov. An open carrier will put much less stress on the axles and carrier and should last an awful lot longer. Besides, it'll feel safer in snow.
 
Hell, if you were anywhere near San Antonio I'd GIVE you the 10 bolt out of my Sub. 4.10 gears, open diff, 30 spline axles, newer brakes with new drums. Always ran Mobil 1 synthetic in it. Only problem? One broken wheel stud.
 
Winter Hill Gang said:
Another question, if I went with a 14bff, and it bolts right up, other than the u-bolt and conversion-joint, the 8 lug wheels would be the only other thing to get right? could they still be 15" wheels or do I have to go 16"?
Click to expand...

8 lug 15" rims fit fine over the 14 FF. You just need to grind a little up front to make em clear the 8 lug front end stuff...

Rene
 
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