clunking sound at rear

Hi all,
i run a 85 ex-US army blazer M1009 while turning i get a loud clunking sound at the rear,this doesn't happen all the time.When it does happen the drive seems to stiffen at the rear axle.Anybody got any ideas????????

My bet is on a genuine locker in the rearend.

*EDIT* - Here ya go: DetroitLocker.com

Hi,
thanks for the answer.Being from the other side of the big pond(England).I take it the diff is up the creek????.If so.is that the complete diff or just a cog or two?

From the symptoms you described, it is an exact match to a perfectly working detroit locker. A locker is a solid connection between the two axles. When it gets resistance - ie. during a turn, the cogs release from each other - before the release you will feel it binding, hear an associated clunk when it releases, and a faint clicking while one wheel is turning faster than the other during the turn.

I think that if you were to pull the rear cover, you wouldn't find the typical diff gears found in normal open differentials. If you open it up and find peices of metal... Well, then you may have to look into a replacement diff (and or ring gear etc). But if it only happens when you turn, it mostlikely is a locker in the rear end.

Hi,
i take it when u talk about a "locker" u are refering to a "limited slip diff"? The diff has never made any noise until about 2 weeks ago.So i presume it has a bog standard diff...which is now up the creek.

Ok. Sorry, I took your post to mean that you just aquired this Blazer and it has this clunk, not that it just started. I miss understood. If it has just started, then I'd say it's time to pull the diff cover off and see what's floatin' around inside there.

Being that it is an ex-US Army Blazer, it probably has a 12-bolt rear end in it. 12-bolt components are pretty cheap and easy to come by so you shouldn't have a problem buying from any of the online retailers (Jegs, Summit Racing, etc).

If you can, take some pics of the inside of your diff. Would be cool to see how one comes apart! Be prepared for a shower of diff lube to come out of it (unless it is bone dry and that is what caused the thing to blow up in the first place).

Good luck!

Hi,right i've had the diff cover off.I have a locking diff.If anyone has a copy of the Us army tech manuals it's fig.113 in TM9-2320-289-34P,differential lock assembly component parts (M1009).The part no 12 on the pic has half it's teeth missing.Which is the best way of repairing this? A complete diff or strip the diff and replace parts 12,9,5x2???


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Yup, that'll do it. You should be able to replace all of the diff internals without pulling the diff housing out. You will have to pull the axles out part way so that you can get the rest of the components out, then you have to pull the diff pin and the rest should rotate out. You may want to drop off the driveshaft as well to make it easier to rotate the diff.

Hi,thanks for the info.Attached is a page from the us army parts book.The items i,ve marked in red,is that all the bits i need to get hold of? or do i need more.Plus have you got any where over there where i can source these parts?


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Well, here's a handy reference I found while trying to track down some parts for your rear diff:
M1009 - Front & Rear Diff Replacement

I'll keep on looking. I could give a call over to a military auto recycler place I know of and see if they have a full diff. That would probably be the cheapest way to do it, but you would have to setup the diff again (shims & new bearings)...

well, i got a quote from a guy here in the UK who breaks M1009's.He qouted me £250 for a diff and £150 for the spur gears and beveled gears.The complete diff swop looks the better option(less work).what do you think?

Don't know how much that is in US dollars, but if the whole diff is rebuilt, I'd go for that. You have a GM Corp 10 bolt front and rear (8.5" dia. ring gear),front with an open diff and the rear with a Gov-Loc differential. From what I have read about the Gov-Loc diff, they are a major weak point and many have upgraded to an aftermarket posi unit or just open if they don't need the extra traction. The problems I have read about are exactly as you have described and some have even gone through 3 diffs before switching it over to a more conventional (new tech) diff. I wouldn't be surprised if you couldn't get a newer style diff over there to swap inplace of the Gov-Loc. You would need to replace the whole carrier however. Check that out as well. Also, IIRC, you have 28-spline axles.

thanks for the info.

£250.00 is about $419 for a second hand diff.What would you recommend as a replacement after market diff.....is there anything made to replace the gogs but using the original carrier?

Hi,What are your thoughts on rippin out the spider gears in the carrier and replacing them with a powertrax lock-right locker??

The Gov-Loc carrier isn't the same as a conventional open carrier or a normal posi. The case cannot take the aftermarket posi's or lockers. If you wanted to go that route, have your mechanic find you a replacement open diff carrier and then replace the guts with the appropriate aftermarket equipment.

This is begining to get on my nerves....lol.The "so called tech" at summit racing reckons the powertrax fits you reckon it don't.So i won't bother with that idea.It's a long way from the UK to the USA to return something.So what do you suggest i shove in it?? Taking into account limited budget and don't want to be bashing the spanners to much.

GM 10-bolt 8.5" 28-spline Gov-Loc differential on eBay.com for $75 now with 3 days left. Shipping to the UK may be a killer, but it looks good. I'm not sure if it can hold a standard posi or not. I'm just going by what I have read on some 4x4 forums when searching the internet on your problem.

Thanks for the info,i'll have a look in a moment.Don't get me wrong i wasn't getting at you in any way.It's gettin to be a pain that's all.I think it would be easier to buy a dodo egg..lmao.