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tribeca09 02-16-2015 12:37 PM

"The two factory pulleys are both 80 mm in outer diameter."

Like I said, no they are not.

The tensioner pulley is 3/8" smaller, and that is not a small difference.

Dodik 02-16-2015 12:47 PM

Not sure why they are not the same on your car, but on mine they were the same 09 tribeca, as well as my old 2002 H6 outback.

avk 02-16-2015 12:49 PM

This contradiction appears difficult to explain, but I am sure it has to be something simple. FWIW, I have a spare tensioner unit (same part number for all 2006-14) and it has a 80 mm pulley.

tribeca09 02-16-2015 12:59 PM

That is bizarre.

The replacement idler pulley (Gates 36330) is the same as the original idler pulley, which measures approx. 80mm. And that is the correct part no. for the idler pulley.

I can find no replacement part no. for the tensioner pulley alone.

The original tensioner pulley is approx. 70mm (or 3/8" smaller than the original idler pulley).

I'm picking up a replacement tensioner assembly (38489) in an hour and should know more then.

Oddly, the only model years for which any tensioner pulley assembly is listed is through 2007 (i.e., 3.0), not beyond (i.e., 3.6). That was the case at NAPA and at

tribeca09 02-16-2015 01:26 PM

Are we sure that the tensioner assembly is the same for 2006-2007 and 2008-2014?

I am finding different Subaru part nos. for the two different series of model years.

For 2006-2007, I come up with 23769AA003, 000, 001, 002.

For 2008-2014, I come up with 23769AA010.

The 38489 replacement tensioner assy. measures 80mm according to the specs online. And it seems to show up for 2006-2007 model years.

I'm wondering if the tensioner assembly changed in 2008-2014, with the switch from 3.0 to 3.6 liters.

Dodik 02-16-2015 01:34 PM

my old 3.0 outback 2002 also had same size pulleys, in fact the first time i was doing them i bought two pulleys and just reused the tensioner.

tribeca09 02-16-2015 01:38 PM

I'm heading over to the dealership parts counter now and will post back. They have the part (determined using my VIN and the part no. ending in ...010) in stock.

tribeca09 02-16-2015 02:11 PM

I just returned with the new Subaru tensioner pulley assembly. It is P/N 23769AA010 and the tensioner pulley itself is approx. 70mm, identical to my original tensioner pulley.

Bottom line, I believe that the 2008-2014 model year (i.e., 3.6 liter) tensioner is different from the 2006-2007 model year (i.e., 3.0 liter).

The belt sizes appear to be different across those MYs too.

tribeca09 02-16-2015 05:16 PM

Can't say for sure, but it might be worth it to somebody, for the 2008-2014 model years ONLY, to try, for the 70mm tensioner pulley ONLY, Dayco 89175, Gates, 36301, or Gates 36174.

The OEM tensioner pulley and these steel pulleys all appear to be approx. 70mm OD x 17mm ID x 33mm Wide (or, in the case of 36301, 33.5mm).

Next time I have to do this again I'll probably try one of these ... hopefully by then somebody else will have confirmed their utility.

avk 02-17-2015 06:30 AM

Indeed the tensioner is different between 3.6 l and 3.0 l engines. I believed aftermarket catalogs showed the same part (which in this case would be OE anyway), but my memory failed me. Yes, a generic 70 mm pulley would be a perfect match.

rickst29 02-21-2015 07:52 AM

That theory fits my B9.
My 2006, 3.0L came with totally identical OEM pulleys (both large).

And tribeca09, thanks for posting your findings about later model years. My recommendation "every 40K miles" would have prevented even the earliest of failures which have been posted here, and on equivalent Outback forum - but I'll SWAG that a 60K schedule would also catch about 90% of failures as well. I also wonder how many failures have been prevented by more knowledgeable, competent technicians checking not just the belt, but the pulleys as a part of 30K/60K/90K "check the serpentine belt" scheduled Service. (Possibly many hundreds.)

I'm unsure why the Subaru 3.0 and 3.6 Boxsters are "more prone" to this failure than other cars which use the same pulleys, and even the same tensioner assembly. (Several GM models, IIRC.) Perhaps the Subaru design has the belt path more fully wrapped around the pulleys, with corresponding higher "sideways" tension on the bearing. (Because the belt route around the pulleys is placed further from a "tensionless" straight-line belt path in our cars, comapred to the GM cars.)

tribeca09 03-15-2015 06:15 PM

I picked up a Dayco 89175, which does appear the same as the 09 MY 70mm factory tensioner pulley. I'm going to keep that, a spare Gates idler pulley, and my old belt in the trunk in case the pulleys begin to make noise on a long trip. I'm also planning to replace them both routinely at 40k miles, which is completely ridiculous but I'd rather that than have them seize unexpectedly.

I got to install some band clamps around my exhaust shields today too. LOL, you'd think these cars are made of metal that is engineered to fail. If my 40 year old Chevelle had airbags I'd drive that daily instead.

tribecadean 03-21-2015 06:22 PM


Originally Posted by tribeca09 (Post 22726)
I picked up a Dayco 89175, which does appear
I got to install some band clamps around my exhaust shields today too. LOL, you'd think these cars are made of metal that is engineered to fail. If my 40 year old Chevelle had airbags I'd drive that daily instead.

I had a temp fix too on my exhaust shields , I like your idea, I took my 06 up to midas and had them weld them...seems like it was 50 bucks or so. been fine ever since,

tribeca09 03-22-2015 10:34 AM

I didn't have the correct size so I used 2 stainless worm style clamps I had from another project, attached them end to end and they fit fine. I did the other heat shield too because it was just a matter of time. I didn't crank the clamps tight, just snugged them enough to cure the rattle.

milo066 04-22-2015 11:29 AM

Replaced the Tensioner and Idler pulleys in my 2006 B9 with the Dayco 89148 as recommended on the Advance Autoparts website. They are spec'd at 82mm and the same as both taken off in that respect. Their construction is different and they are chromed, not what I am used to or like the ones I took off. Advance offers an OEM spec on their website for delivery to you, not available at the store. I'll do that next time (Litens Pulley 900558A). I bought 2 new washers at Subaru for $2 each just for the heck of it. One of mine was galled from the Tensioner pulley having frozen. Was a simple job, thanks to the Rag tip! Boy I am glad I read this forum before I took the pulleys off! As for the 70mm pulleys, it would have made getting the belt on a little easier but realize the smaller diameter will spin the bearings a smidgen faster than the 80mm version. Also makes the U-turn of the belt a bit easier flex wise...

avk 04-22-2015 08:28 PM

70 mm is for 3.6 l engine, the dimensions are not identical to 3.0. The Litens unit looks like another aftermarket alternative but not identical to the factory part.

Dodik 04-23-2015 07:05 AM

why is everyone replacing pulleys, it takes 5 min to swap new bearings in and they are much cheaper.

psygnal11 04-24-2015 06:18 AM


Originally Posted by Dodik (Post 23025)
why is everyone replacing pulleys, it takes 5 min to swap new bearings in and they are much cheaper.

Agreed. Timken 203FF -or- SKF 6203-2RSJ. No need to replace the whole idler unless it's damaged/deformed.

singincanary 05-02-2015 08:54 PM

Without a press it is difficult to replace just the bearings.

avk 05-03-2015 11:29 AM

A hammer and correctly sized sockets seem sufficient to apply the necessary force in this case, but on the other hand, generic pulleys are easy to find under $15.

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