Hey guys,

I am pretty ignorant on this rear axle stuff still, but I'm learning. Can someone confirm for me that this is indeed an LSD pumpkin? I don't know how to tell the difference between an LSD differential and a regular open/non-locking differential. The seller claims it is an LSD rear out of an 83. He says there are 24 splines for the axle and it has 3.90 gears. This would mean that it has small axles and will drop right into the 83 rear end that I have. Everything should be a straight swap for me. All I need to do is change over the driveshaft to accomodate the difference in flanges, since mine is a large flange rear end. All this sounds right to me, but I want to be sure. Here are the pictures. Help is appreciated.

Jamie

 

Looks like it, another way to confirm is to look straight through the axle holes, LSD will be straight through, where the open diff will have a pic going across right in the middle.
If this rear is from a 83 you won't have to change driveshafts....

 

I think it is; the photo is not great.
in the lower photo, look on the right side, at the rectangular window in the diff.
I believe I see the clutch plates and bellville spring thru that window.

 

Sean,

I thought that all 83's had the big flange rear end with bolts and nuts? I know that mine does at least. This one in the picture looks like a small flange diff with the threaded holes. I'm pretty sure it is a small flange diff anyway. I was just assuming that I'd have to change driveshafts cause they sure look different to me...

Jamie

 

Looks like it's seen some abuse. Is it normal for them to be that filthy?

 

I was pretty sure that the large flange went hand in hand with the large axles...

 

If it is small flange, it is '82 or earlier.

'79-'82: small axle, small flange
'83: small axle, large flange
'84-'85: large axle, large flange

 

I think that everyone has been misinformed about this by some of the generally accepted information around here. My 83 is DEFINITELY not this way. It has the large flange rear end and small axles. Absolutely 100% sure.

 

Looks like a LSD. Check the difference in the drawings of the two in the FSM. Also, you could swap your shaft with the shaft on that diff if you want to keep the large flange.

 

Yeah, I tried looking through the FSM's like you suggested but didn't find anything to definitely confirm that it was a LSD. I guess I'll be able to tell for sure when it arrives. The guy that I bought it from is shipping it tomorrow.

As far as swapping the flange on the diff, how hard is that? I was thinking that I would just get a 79-82 driveshaft, and that way I'd have the removable u-joints. My 83 shaft has the non-removable u-joints which IMO is a terrible idea by Mazda. I thought I'd just go ahead and remedy that problem while I was at it....

 

If you were not planning on rebuilding the LSD, get the driveshaft. Swapping the tail shaft requires the diff to be taken apart, along with preload and backlash reset.

 

100% sure its an lsd can guarantee it an open diff you can see the spider gears and it doesn't have an enclosed case to hold the shim packs. trust me i have rebuilt a few diffs lsd included i have an lsd from a fc sitting in my garage also that im about to rebuild also.

 

yeah, in the second picture you can see the clutch disks.

 

Yep 100% lsd. You dont' need to see clutches. Look just left of the ring gear. See what looks like two spacers, thats because the far left is the top cover of the lsd case- what you take off to get all the clutches and gears out of. If the front flage has threads in the 4 bolt holes than this lsd is out of an 81-82.5 gsl-small axle, and is what the old school guys, like me, bolt right into their rx2 and 3's

 

The three I took apart were similar in colour, but didn't have all the particulate all over them. Looks like this one has been sitting around collecting dust and debris.

 

ultimatejay got it right ... here's mine ... now you just need to clean yours up like mine

 

So what's the best way to clean this diff? I was thinking about just pressure washing it at the car wash, and then letting it dry off really good. Probably blow it out with some compressed air too. Is that going to hurt any of the internal parts? I can see how I would get some flash rusting if the parts are wet...

Jamie

 

Brake cleaner or some other solvent, not sure I'd use water unless you can dry it really well right afterwards to avoid rust.
I can't tell from the pic which flange in on there, but either way changing driveshafts is no big deal, and like you said then you get the replaceable u-joints.

 

WD-40 is a good solvent that won't hurt. Thats what I used on mine:

 

Sgt,

What do you need to buy to rebuild an LSD? I was thinking about freshening it up before I put it in, but didn't know what kind of cost I would be looking at for parts.

Jamie

 

For mine I used POR-15 to do it, and I think it came out pretty darn good. When you buy their starter kit which would be more than enough to do a project like this, it will include a degreaser, a zinc phosphate spray to neutralize rust, then the por-15 color that you want to paint. But basically how I cleaned mine was by keeping it assembled to the rear end, and sand blasted the whole thing. With POR-15 you don't have to be too precise weither it still has some rust or not as it will neutralize it.

 

I did the same, sandblasted with it assembled to keep teh sand outta there, then took it apart to clean the inside with brake cleaner, then sealed it all up with por15 and some undercoating. Came out very nice