Overrunning Alternator Decoupler (OAD) Pulley Mod

The part number that potentially fits the 1ZZ is Gates 37225P

I just called my local O'Reillys and there is not a single one in stock in my city. Would have to be prepaid to get one in front of me to measure.

@marsrock7

Have you actually put the 1zz pulley up against the 2zz to see that it’s smaller? The other thing, is the alignment with the belt the same? 

I’m not trying to be difficult but trying to get as close as we can before someone spends unnecessary time and money on it. 

I was going to take a better look  and maybe pull my alternator this weekend but ended up installing a Scion radio in my wife’s car for her B-day. Today I’m dealing with pack rats again.

Welp, the closest O'Reillys to me is over 100 miles.

Posted by: @suoiruc

@marsrock7

Have you actually put the 1zz pulley up against the 2zz to see that it’s smaller? The other thing, is the alignment with the belt the same? 

Better than, I have measured both with a caliper. 2zz is 55mm, 1zz is 52.5mm. The alignment is the same, and they could be interchanged if desired. 

I can already confirm the 55mm decoupler pulley named in the beginning of this thread is an exact fit replacement for the solid 2zz pulley, which means it could also be used on the 1zz alternator, but would yield a ~4.5% underdrive. I suspect, as with the 2zz swap, the OEM sized 1zz belt would likely still fit, but very tightly.

The potential 1zz pulley direct from Subaru is p/n 23752AA150. Maybe I or another can find one at a Subaru dealership without having to get it ordered in. 

Liten's p/n 920054A

I can check my local subaru dealer and if they have one, what am I measuring? Do I have the tool to measure?

Posted by: @haloruler64

$43 for the Gates, I might give it a shot. Need to order a caliper from Rock Auto anyway, might save on shipping. Anyone got a discount code? 😛

11605463224694582 for 5% off

Posted by: @hello

I can check my local subaru dealer and if they have one, what am I measuring? Do I have the tool to measure?

Primary concern is that the pulley has m14x1.5 threads, so if you have a bolt of that size and thread pitch (or an alternator without a pulley) the pulley should thread onto it.  Also, if you have a caliper, a double check of the OD size as pictured:

And a measurement of the thrust from the alternator side of the pulley to the first rib as pictured:

If the threads are right and the measurements are close to what I have, the subie pulley should fit the 1zz no problem.

@marsrock7

I removed my 1zz pulley today and took some measurements. It was quick and easy with the impact with 22 mm standard socket and this was done without removing the alternator.

The first pic shows a dimension i thought might be important since that portion slides into the alt housing; probably not a problem if not much larger in diameter.

@souiruc 

I measured mine as well just now and got the same, ~34mm on that area (pulley seat?). I also just measured the space it seats in and it is 35mm, so 34mm is the MAX allowable "pulley seat."

Here is a picture of the "seat area"

The inner race of the bearing has an OD of 24mm, and it is the only part (besides the shaft and pulley bore) making contact with the pulley itself... Therefore, I am confident any "pulley seat" between 24mm and 34mm should function without issue, as long as ID (bore) threading and OD match up. Example: the pulley off of my aftermarket alternator has a "pulley seat" of only 28mm.

It's great to hear you were able to zip the pulley off without having to pull the alternator itself. I'm glad some impacts fit.... Mine is bulky and I definitely can't get it in there.

Also... Do I read your caliper correctly and that is a 55mm pulley? On your 1zz?

@marsrock7

Wow, lol, I just did the conversion! That does come out to 55 mm. Is this correct or are you measuring down into the groove? Never mind, that wouldn’t make much sense to measure down in the groove.

This is off an 03 1zz. Are they using two different size pulleys on these? Maybe the 02s and earlier are smaller or maybe the SMT uses a larger pulley? So I can use the pulley that was originally stated?

Your conclusion on the seat i think is good. It was a bit hard to get the calipers into the alt housing and measuring that while in the car.

@suoiruc

It appears there are two different sizes... Mine is an 01 and came with a 52.5mm... yours has a 55mm. The measurement is taken from the top of the teeth, not in the groove. So yes, it appears you could have used the same pulley as for 2zz, and you are now overdriving your alternator just slightly.

So which pulley did you end up using? And how do you like the change?

Called a dealer yesterday, got hung up on. Emailed them, no reply. Emailed another one, also waiting on response. I don't have your tool to measure :/

@hello

No worries, it seems @suoiruc has one this conversion on his 1zz, just waiting to hear which pulley he used.

@marsrock7

I don’t have a decoupler pulley since I’ve just been trying to determine which size to purchase. Glad I waited or I’d have the 52.5 mm pulley, not that that would make a significant difference. I need to order one from ebay when I get around to it. 

This has been interesting and I will let you know how it turns out.