3.73 or 3.90

[BennyBlown2v]

A bit of tech for you instead of an opinion.

When you have the installer put your gears in, tell them you don't want them to use a crush sleeve. Tell them to make an appropriate sized shim instead.

I would see how that could work, but what would the benefit be? Crush sleeve is fine as long as you take your time and set it right :-\ I mean it would be great if it was just a spacer so you could pull the gears whenever you want to change seals and stuff, but at the same time whats the point?

 

[Rusty67]

The point is that once the rear end is setup properly with a shim, you can pull it appart yourself and put it back together yourself any time you want and don't have to worry about screwing up the backlash. That and the fact that any shop that is compitent enough to actually make a proper shim will setup the rear end correctly so you wont have any gear whine.

 

[BennyBlown2v]

The point is that once the rear end is setup properly with a shim, you can pull it appart yourself and put it back together yourself any time you want and don't have to worry about screwing up the backlash. That and the fact that any shop that is compitent enough to actually make a proper shim will setup the rear end correctly so you wont have any gear whine.

The crush sleeve doesn't have anything to do with backlash, it just effects pinion bearing preload. It doesn't even effect how deep the pinion gear is in the housing; the depth of the pinion gear is set by a shim which is fitted underneath the pressed on bearing. The crush sleeve is there because you have to tighten the bearings to different specs depending on if they are used or new - with just a spacer collar instead of a crush sleeve you wouldn't be able to change the rotational drag of the pinion gear (the preload), so if you changed bearings you would somehow have to make a new spacer and get the preload just right with it torqued all the way down. Also, if you over torque it too much you will ruin the bearings and races, so that would suck also.


I have never seen or heard of anybody using spacers instead of a crush sleeve, it just doesn't make sense when a crush sleeve is so easy to use and so cheap to change out if you need to.

BTW, if the pinion depth doesn't change, and you have the gears set to the proper backlash, then you SHOULD be able to pull the carrier out without replacing or changing those shims at all anyway - but often times the carrier races, bearings and shims go bad, especially if the carrier isn't properly loaded into the housing, or if the end caps go bad.

EDIT: also, just because you get everything into spec (ford, gear manf., or whoevers) doesn't mean there won't be SOME whine and/or vibration at varying speeds. There is a lot more to rear end setup than just getting things into spec numbers wise; much of it has to do with feel and look of things as well. Hell, stock gears vibrate like a mofo over 150

 

[96GTstang46]

Not to be weird, but thanks BennyBlown2v, You really schooled me on that issue.. lol I didnt know THAT much into gears and set ups.... that was alot of great infomation that i never knew!

 

[Rusty67]

The crush sleeve doesn't have anything to do with backlash, it just effects pinion bearing preload.

You sir are correct. I was mistaken when I posted that.

The reason I initially said that a spacer is better then a crush sleeve is that when I took an ASE manual trans/transfer case/diff class the teacher (who is an ASE master tech) told us that for performance applictaions a true spacer is better. Now, I went and read up a little on this subject because its been a while since I took that ASE class and we didn't really cover differentials/transfer cases too heavily.

Besides what you have posted about being able to change your seals without having to redo your setup, there is at least one advantage to using a spacer over a sleeve. The nut that holds the pinion on is a lock nut and will hold fairly well, but in perfomance applications, it is possible that you can't get enough torque on the bolt because if you tighten it, the crush sleeve will crush more instead of holding the torque. Using a spacer allows you to put far more torque on the nut and not having to worry about the crush sleeve deforming.

I admit that this benifit doesn't really add anything to most street cars. The practice seems to be in use more for offroad 4x4s and for cars with locking diffs.

I am still surprized you have never heard of anyone using a spacer instead of a crush sleeve.

 

[03ghoststang]

The crush sleeve doesn't have anything to do with backlash, it just effects pinion bearing preload. It doesn't even effect how deep the pinion gear is in the housing; the depth of the pinion gear is set by a shim which is fitted underneath the pressed on bearing. The crush sleeve is there because you have to tighten the bearings to different specs depending on if they are used or new - with just a spacer collar instead of a crush sleeve you wouldn't be able to change the rotational drag of the pinion gear (the preload), so if you changed bearings you would somehow have to make a new spacer and get the preload just right with it torqued all the way down. Also, if you over torque it too much you will ruin the bearings and races, so that would suck also.


I have never seen or heard of anybody using spacers instead of a crush sleeve, it just doesn't make sense when a crush sleeve is so easy to use and so cheap to change out if you need to.

BTW, if the pinion depth doesn't change, and you have the gears set to the proper backlash, then you SHOULD be able to pull the carrier out without replacing or changing those shims at all anyway - but often times the carrier races, bearings and shims go bad, especially if the carrier isn't properly loaded into the housing, or if the end caps go bad.

EDIT: also, just because you get everything into spec (ford, gear manf., or whoevers) doesn't mean there won't be SOME whine and/or vibration at varying speeds. There is a lot more to rear end setup than just getting things into spec numbers wise; much of it has to do with feel and look of things as well. Hell, stock gears vibrate like a mofo over 150

you are correct on this, because there is alot more than just an "install" theres been numeorus times i had to pull that sucker appart just to get thecorrect backlash....and using FRPP gears makes the install easier because you dont have to do all those steps to find the pinion depth

 

[TrueBlue03]

As 04yellowGT mentioned, also take into consideration your exhaust tone on the highway. i'll be going with 3.73s instead of 4.10s just because at 65+ mph, my car would be roaring so loud that i couldn't hear myself think.

 

[hotmustang331]

I have FRPP 3.73 gear and they were GREAT N/A....loved em. But now iwth the turbos...I just run out of gear way too fast, and they dont load the car up enough.

Stock 3.27s will be going back in shortly....who would have thought LOL