Help! Gates idler pulleys

I bought two upper and one lower idler pulleys from rock auto. They only sent me one shim so I’ll have to use an OEM one in the time being until they fix that. I was wondering if the shim goes in the front or the back and do I use the OEM washer on the back?

 

The shim I am referring to.

 

And the washer

 

On the lower there is a shim in the back washer in the front…

 

No one? I’ll just go with shim in the back OEM washer in the front.

 

It's hard to say without seeing it in place. Just make sure the pulley spins freely once installed. I had to reuse a couple of my shims/washers behind my new pulleys.
You can also, carefully, remove the dust cover from your original bearings, clean them out with some brake parts cleaner and repack them. I don't know how long this will last, but will get you by in a pinch.

 

Spin freely as in smooth? Or no resistance? Because they all definitely have some resistance, even before installing them.

 

You want a little resistance, a newly greased bearing won't just free wheel, you just don't want it to be in a bind.

 

I would guess the shim goes in the back so the pulley does not rub against the engine.

 

A few years ago, I also ordered and received a pair of Gates idler pulleys without shims. I sent them both back, and replaced the bearings in the OEM pulleys. In January of this year I replaced the water pump and - while I was there - installed these;

$29 labwork Idler Pulley Kit Replacement for Toyota 4Runner Tacoma Tundra Hilux 4.0L V6 1GRFE 2003-15

https://www.amazon.com/gp/product/B07VV9FYNK $30 for all 3! To date there have been no issues!

 

Shim in the back, washer in front


Weren't you paying attention when you took it apart?

 

I was up until 2AM and I was hyper focused on getting the water pump off… overlooked how the pulleys were assembled.