Overrunning Alternator Decoupler (OAD) Pulley Mod

Ah, I see. The alt shaft has a hex key hole in the end, but it would be blocked by using a larger, solid hex key on the pulley wheel.

So you'd need a 17mm hex key for the pulley wheel with a hole in the center for the hex key used to immobilize the alternator shaft. Perhaps acquiring or fabricating that is still easier than removing the alternator?

What about using a strap wrench on the wheel itself? Maybe a strip of rubber (bicycle innertube) to improve grip and protect the wheel? Or is that the wrong direction?

Just took a look at my spare alternator, the end of the shaft appears to be a 10mm hex. So to make this work with alternator on the car one would need a hollow 17mm Allen (which is available in most decoupled pulley service kits) and a thin walled 10mm socket to immobilize the shaft. Most newer alternators use an insertable bit to hold the shaft, not a socket, so this tool would likely need to be fabricated. 

If someone finds a way... Awesome. But if it can't be done without a tool that would take several hours to make... Pulling the alternator and putting it back in should only take 2 hours tops...

I don't think the strap wrench would work, because the pulley needs to be able to turn, and the shaft needs to be immobilized. A strap wrench would only be holding the pulley... 

Having replaced the alternator three times it has damaged my motivator.   

I've done it three times now too. First was definitely worst. I can pull and replace in about an hour now. Hanging the bottom bolt is still by far the worst part.

I couldn't get our tool kit at the shop to work, it's made for an alternator shaft which has an internal key like a Torx or Allen. Our alternator shaft has an external hex. I just smacked the pulley with my air impact and a 17mm 1/2 drive hex bit to take it off and put it back on the same way. The impact hits fast enough to impart enough torque to affix it to the shaft. Trying to hold the alternator from spinning just wasn't possible in this case.

@bitter

It looks like this can be done without removing the alternator. There seems to be enough room for an impact, not being sure how much deeper the new pulley will be, but with the original pulley, there’s plenty of room. Question is, will the pulley referenced earlier in the discussion, work for the 1zz? Is it the same diameter?

Someone take a caliper and measure the OD (in the belt area, not the lip) of their 1zz alternator pulley. If I find mine in the garage I'll measure it, but haven't found it yet. OD of the decoupler pulley is 55mm, as is the 2zz alternator pulley. I'm almost positive they're the same, or at least close enough to not matter.

I found my 1ZZ alternator this morning! The pulley that is on it is 52.5mm, so there is a slight difference. Installing the 55mm pulley on a 1ZZ would result in a ~4.5% underdrive, which may be of further benefit to some, but not recommended for heavy energy users like those with aftermarket audio that wants more juice. Maybe there is a decoupler pulley that fits perfect, will have to do some searching.

On that note, I just checked a Toyota parts site and all 1zz and 2zz alternatora are 12v 80A. If the crank pulley diameters are the same between 1zz and 2zz (cannot verify firsthand), is the alternator pulley diameter the only reason we have had failures of the 1zz alternator on a 2zz? Would throwing a 55mm pulley on the 1zz alternator be enough for it to survive 8000+ engine rpm?

Posted by: @marsrock7

I found my 1ZZ alternator this morning! The pulley that is on it is 52.5mm, so there is a slight difference. Installing the 55mm pulley on a 1ZZ would result in a ~4.5% underdrive, which may be of further benefit to some, but not recommended for heavy energy users like those with aftermarket audio that wants more juice. Maybe there is a decoupler pulley that fits perfect, will have to do some searching.

On that note, I just checked a Toyota parts site and all 1zz and 2zz alternatora are 12v 80A. If the crank pulley diameters are the same between 1zz and 2zz (cannot verify firsthand), is the alternator pulley diameter the only reason we have had failures of the 1zz alternator on a 2zz? Would throwing a 55mm pulley on the 1zz alternator be enough for it to survive 8000+ engine rpm?

Interesting observations.  In regards to the 2ZZ alternator  from what I did read in the past it is supposedly different in two key areas which is the bearings and the rectifier.  It is also possible that under driving it might be a third reason.   

Also not all 2ZZ alternators are the same. Apparently there is a different part number or the lower limiter XRS models. I found this out when I was buying a replacement from AutoZone. I had to buy the earlier Celica GTS version.  

I found one that seems to be an exact for for the 1ZZ, 52.5mm OD, 17mm bore, 6 ribs. Gates 37225P 

This one fits multiple Subaru 2.0l and 2.5l vehicles year models 2015-2018. For part hunting: fits 2016 WRX with 2.0l

Who wants to be the guinea pig?

Warning: thread pitch of m14x1.5 is currently unconfirmed. If anyone's local parts store has one of these in stock (none of mine do), it would be a huge favor to all that are interested to take a measurement!

@marsrock7

Great work! I’ll see if that’s available on ebay. I’m assuming (i do that way too often it seems) the thread pitch is the same? 

That makes sense the 2zz has a larger pulley due to the higher rpm engine. I think you nailed it!

Posted by: @suoiruc

@marsrock7

Great work! I’ll see if that’s available on ebay. I’m assuming (i do that way too often it seems) the thread pitch is the same? 

That makes sense the 2zz has a larger pulley due to the higher rpm engine. I think you nailed it!

Good catch.... Although I would like to believe the inner bore, and some semblance of standardization, dictates the thread pitch, I am not 100% sure of that. After about an hour of frantic google-fu I cannot seem to find proof that the listed pulley has m14x1.5 thread pitch as our alternators do.

O'Reillys seems to have the best searchable (but small) pulley database. Without entering a vehicle one can search through all available pulleys by inner and outer diameter and number of grooves. The fact that thread pitch is not a definable option is what leaves me to believe there is some sort of standard defined between inner diameter and thread pitch. My TSX alternator uses a 17mm ID pulley and the thread pitch on it is also m14x1.5.

@marsrock7

Oreillys has it for ~$117 special order. That would give the opportunity to verify fitment. Ebay shows one for $48 but probably wouldn’t be returnable.

I don't want to jerk O'Reillys around and make them order me a part I don't actually intend to buy. Maybe I'll go to a store and see if they can locate one in my city, and if one is around go to that location to take measurements.

I am with Haloruler in that I don't understand how any of this works but am interested to make this happen. I don't mind jerking O'Reillys around except I am not sure I have one near me but I can check. What's the part number I want?