12 Bolt question

[DavidB]

Going to be ordering a new 3.73 ring and pinion and eaton unit for my 71. I know depending on your ratio you have either a 3 or 4 series, one of those has a thicker ring gear than the other. If I'm replacing everything does it matter if it is the same series that came out?

[Shaky]

It doesn't have to be the same ratio as the one that came out as long as the carrier and the ring gear are compatible.

I took a '71 3.73 open and put in an Eaton cone posi with 3.07 Richmond gears. Set everything up with new bearings. It's all good.

[LONGHAIR]

Nope, it doesn't matter at all.
But, you would be ahead to find a professional to do this swap for you. Changing gears is a very involved and precise process. It is really not worth the trouble to learn or the investment in the required tools to do a job that you will probably only ever do once. Plus there is still no guarantee that it is right.
If you pay a pro, you have none of the frustration, all of the warranty and none of the investment in tools that you won't need for anything else.

[cdowns]

plus you should be got all new axel bearings seals to do the job right the first time// yes it costs to have pro do but well worth it in my opinion

[big_al_71]

+1 with cdowns!!!!!

[Shaky]

If you're good mechanically, have time, and are very patient, you can do the job.

Setting the pinion depth is the the most difficult thing. It's also critical. I don't know what kind of friends you have or what tools you have access to, but if you can't figure out how to do this, then you should probably listen to the guys who posted above.

The next most difficult thing is setting up the pinion bearings with the crush sleeve. If you go too far, you have to take it apart and get another crush sleeve and try again. Access to a press to put the bearings on is almost mandatory.

The carrier bearings aren't too bad, but require patience since you are doing two things: setting the preload on the bearings and moving the ring gear relative to the pinion in order to get the right static pattern.

If you have more time than money, decent skills, and access to a few tools, you can pull this off. Otherwise it's probably better to pay somebody.

Mine came out fine, but I set it up in the basement during the winter and took my time...a lot of time.