According to your post, it says an AT pumpkin will not work no matter what. Shop said there is no problem making mine fit, they just need to order the right shims but other then that all is well. When he put my Quaife and 4.08 gears in, there was too much back lash whe he used the original shims.

Hi,

Can you confirm if I can retain the AT differential please? And does anyone know where I can buy a full set of shims online?

Cheers!

You CANNOT retain the AT diff. You can use the AT pumpkin/shell but not the actual diff itself. A set of shims is all custom ordered. There is no set shims that magically work. Every thing with the diff is custom fit. Shims can be ordered from .005" to .060" in increments of .005 at $16/pair from Courtesy Nissan and its not likely that you will use the same size on both sides. YOU have to measure the shims and find out which size your need unless you just order them all and figure out which ones you need.... Not only that you still need to measure the pinion depth for backlash. I learned after about 8 hours of shimming that I should let a shop take care of it as this is my first diff but without all the shims at your disposal much less measuring everything to the thousandths of an inch.... Without the proper tools and measuring equipment, there is just no way to install the 4.08 gears and diff properly.

Alright. Thanks a lot for your explanation. Appreciate it!

Very well said.

The ring and pinion sat in the AT housing of a 370/350. The only problem was that we couldn't get the gears to mesh properly and it seemed like it required a ton of fiddling & shimming.

I now understand since the shop contacted me yesterday morning. They are actually having to get custom shims cut to make it work. Labor wise, they are charging me a flat rate. The shims custom made are gonna cost me an extra $75.

yeah when i did my quafe in a manual shell i need to grind a custom shim for one side. you have to juggle 4 things when you do it. preload on the carrier bearings, preload on the pinion bearings, back lash, and the contact pattern. it's a bear.

What happens when there is too much backlash?

You will have a sloppy install & your gears will wear out faster. Backlash is the amount of play or slop between the pinion & ring gear. You need some, but too much is a bad thing. It will also affect the pattern.

Thanks for explaining

Not too mention will make it whine like CRAZY! I had the Momentum headers, Z1 test pipes, and Litespeed exhaust and the whine would actually drown out my exhaust when the backlash was set too far off. It would only whine on decel though.

The gears are awesome. Got Quaife + 4.08 FD nissan gears. The car moves really well.

I can add a few engine mods to add a bit more power. Better wheels+tires and a lighter flywheel will also help.

The Z can be made really awesome...

4.363 FD + OSG Super L0ck + SPL traction bars & AL diff bushings + YokoHama AD08R = :rock:

Vids??^^

I've come full circle now. At about 32k miles I swapped to 4.08 gears. Then just about a month ago at 76k miles, I swapped back to the factory 3.69 gears. For the record I've got a 6MT.

I miss having the 4.08's driving around town. Ripping through 1st, 2nd, and 3rd gear was so fun.

Highway driving is more fun now with the 3.69's. Rolling at 70 then drop it into 3rd and just let it go. Shift to 4th then hold it until .....

Going from 4.08's back to 3.69's makes the car 'feel' slower because it's not revving as quickly.

Why did I swap back to stock gears? Got tired of the gear whine.