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Is a 4.22 carrier the same as a 3.90?

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or is it offset less? I know w/ 9" Fords and such there are 2, 3 and 4 series carriers but what about these? Later type of diff of course.
 
Yes and No. There are two types of carrier cases. The one with the passenger side fill hole and the ones without. This usually distinquishes the pinion bearing sizes used. If memory serves me correctly, there are two different OD's of the front pinion bearing. The ID is the same. Opposite condition on the rear pinion bearing. Same OD, but different ID to account for the different pinion shaft configurations. One is a stepped configuration using a 1.1875 shaft diameter on the gear end and stepping down to a 1.000" diameter at the front (flange) end. The other is a consistent 1.000" shaft diameter.

AS with all things BLMC, it is best to inspect and find out exactly what you have. Mixing and matching of cases, gears and bearings is not uncommon. I've done this dozens of times when setting up Limited Slip Diffs or building one from a gear set for racers.

If this is a simple question of will a 4.22 from an earlier car fit the axle housing where a 3.9 used to be? The answer is YES it will regardless of the carrier. It is exactly the same bolt up, shape, size and fit up to the drive shaft.

Lots more details could be written, but not necessary unless required.

HTH,
Mike Miller
 
MIke, allow me to clarify. Not will the chunk fit in the housing; will 4.22 gears work on a 3.90 carrier: as in just the center part that the ring gear rides on.

Let's say I have 3.90 gears in my car and a spare loose set of 4.22's ( just the ring and pinion). Can I swap out gears and reset to proper specs, or do I need a carrier that isn't offset that far?
 
Billy
Before you do that I'll swap you a complete and ready-to-go 4.22 and i'll even pay for you to ship the 3.9 to me!!
BillM
 
My experience has been that when trying to do this with lower ratios moving into higher ratio carriers, it often requires adjustment of the ring gear carrier position (side to side). I've had more successes going the other way, like a 3.90 gearset going into a 4.22 housing. What you ask can be done, but it will require shims and spacers that are most of the time NLA. And, maybe a new inner pinion bearing if the diameters of the pinion gear shaft are different. A good bit of work and a little bit of cost. Again, yes you can do this, but it will be some work. No, a different carrier is not needed. All of them are the same except for the machining tolerances.

I would take BillM up on his offer. It is the better option.

Mike Miller
 
I don't want or need a 4.22 but I need a new carrier. I figured since the 4.22's bring less, it would be better to buy one of those v.s stripping out a good 3.90. I have a good 3.90, but I want to keep it intact. I'm building another diff, but my carrier is a total of .007 out and I want to get another one. (.002 in one direction ande .005 the other.)
 
Okay, I think I know what you are trying to do. You have some 3.90 gears and a separate complete rear diff assembly. You put the gears into the assembly and they don't mesh quite right. 4.22 assemblies are cheaper out in the www: than the 3.90's, so you were going to buy one of those and put the 3.90 gears on the carrier in it and put it in your housing to correct the mis-alignment. Am I on the right track now?

The only problem with this approach is that it is hit or miss. You migh get one that is just about right and you might get one that just changes the numbers a bit or not at all. This goes back to your original question. The carrier in the differential, whether it is 3.73 to 5.38 is going to be unique to that specific assembly. They can be moved from one assembly to another with adjustment. You might find exactly what you need if you have a large enough supply of assemblies to pick from.

Usually one has to change the spacer washer to fix the in/out of the pinion gear. The side to side fixes usually involve shims behind the carrier bearings and adjusts the ring gear. I don't think you can fix the in/out of the pinion gear with a carrier alone.

Am I getting closer to figuring it out? Or am I still on the wrong track and confused. If you are looking for/want just a carrier, I have just those. If you want all that is left of a bad 3.90 (bad gears - everything but the gears), I have that too. How can I help?

Mike Miller
 
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