Subaru R180 diff clunking

arcdef

Club Member
Hey guys,

Got the Z out for the first proper drive this year since fitting the Subaru R180 LSD and I am concerned with its performance.

If travelling at any speed under 15-20MPG and applying any steering and accelerator input the diff has a very loud clunking. Any speeds over that and if I coast the diff is silent.

Any other owners with this diff fitted experienced similar behavior or do I need to get this rebuilt?

I understand that some LSDs can chatter at low speeds on full lock but this is surprising for what is meant to be a road biased diff (i don't know the history so could have been modified in the past).

Thanks!
 

jonbills

Membership Secretary
Staff member
Site Administrator
are you sure its the diff, not driveshaft/cv flange bolts loose?
 

arcdef

Club Member
Not had a chance to properly inspect. The CV shaft has integrated splines which slide into the diff and no play at the 'hub'. need to jack it up to check the driveshaft though.

Wouldn't these being loose also cause noise when going straight/at higher speeds though?

I forgot to add to original post but you can feel the wheels almost skipping when it clunks.
 

atomman

Club Member
What type of LSD unit is in there ?

Clutch type are a bit noisier but not much , SureTrak and Torsen a little quieter. I changed my Clutch type to a Torsen last winter but not to much difference to be honest,

if its clutch, how much grab is it set to ? , also if its clutch type have you got the right oil in it ? they do sound clunky if you haven't got 90A LSD oil in there
 

arcdef

Club Member
I purchased the diff on ebay as a working diff months ago but the advert didn't stipulate that is had been modified at all. It sounds like im running over some metal when it clunks so wouldn't say it falls into the "bit noiser" camp lol.

I have put in Motul 90 PA Mineral Limited Slip Differential (LSD) Oil.
 

atomman

Club Member
I purchased the diff on ebay as a working diff months ago but the advert didn't stipulate that is had been modified at all. It sounds like im running over some metal when it clunks so wouldn't say it falls into the "bit noiser" camp lol.

I have put in Motul 90 PA Mineral Limited Slip Differential (LSD) Oil.

Did it say what type of diff it was ? or what car/year it was out of ? I could work it out then

If its a clutch LSD that's the right oil, It if not then it should be normal hypoid,

but it does sound like a clutch type to me as its not slipping when your going round a tight corner , hence the skipping , which means you could set it to slip more to solve it..
 

arcdef

Club Member
I cant view the actual ad anymore but description was this: Subaru impreza turbo newage 6 speed R180 3.54 Rear LSD diff differential 39 / 11

What would adjusting it entail?

Thanks for the help so far guys!
 

Fairlineguy

Club Member
From what has been said I’d guess it’s a clutch lsd .
I’d check the breakaway torque is set correctly you could try adding some friction modifier.
 

arcdef

Club Member
I've ordered some redline friction modifier to see if that helps if not I guess I'm going to have to pull the diff and get it adjusted/rebuilt :(
 

status

Well-Known Forum User
I’ve got two imprezas an sti Uk car and a jdm wagon,my sti did the exact same thing on full lock when I first got it so I changed the oil in both diffs and it’s sound as a pound,these diffs don’t like dirty oil so It might be that its dirty or been sitting for too long
 

arcdef

Club Member
Half a bottle of redline friction modifier has stopped the clunk completely! Hopefully it lasts else I guess I need a rebuild.
 

240L31

Club Member
I had the same issue and got wise advice from @atomman : only use motul 90pa oil. I couldn't believe it, all low speed noise is gone since I changed the oil.
 
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