Rear Diff options?

M

mk8fanatic

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I was thinking of having my rear redone, and I would like to get all the parts needed myself. I am not too familiar with what all it would require to have someone make it a Track Lock or "posi".
First I know I need the ford 8.8 gear set and a seal and bearing kit, but when it comes to the tracklock part is where I get confused.
Does the Mark viii come with an open Diff? If so I guess what I need is a 28 spline track lock diff to replace the "open" diff?
Has anyone had any experience with a mini spool?
Also I will need to know any other parts it will required for the job,and the best priced place to get them. Any help would be appreciated.
 
You want a 28 spline "IRS" differential. The Ford traction-lok is a good in-expensive setup and is rebuildable. Usually you can find a good deal on a used one and rebuild it good as new. You can use a non-IRS unit if you remove the circlips from the end of the half-shafts that go into the spider gears.

If you start with a used housing, you can build the rear end in the used housing and install it with minimal downtime. It's actually fairly easy to swap the housings out. Then you can sell the one you swapped out and recoup the cost of the used unit.

You should be able to buy a used housing for $150 and a used traction-lok for less than $100. Here's some other part numbers and old pricing:

Ring & Pinion(4.10s) / M-4209-G410 / $149.25
Installation Kit / M-4210-B / $78.20
(2) axle seals / $16.84
(2) axle bearings / $20.00
(2) axle nuts / $12.28
Trac-Lok Rebuild kit / M-4700-B / $39.10

Budget some some gear oil and friction additive too.
 
I went w/royal purple gear lube it already has the additive and ended up costing a few bucks less than lube and additive. I've put a few thousand miles on the posi/gears works perfect!
 
merkurmadness said:
I went w/royal purple gear lube it already has the additive and ended up costing a few bucks less than lube and additive. I've put a few thousand miles on the posi/gears works perfect!
Click to expand...

Not trying to be combative, but I've got to recommend against Royal Purple. This stuff continually fails corrosion tests, and there are some guys on this board who have been a victim of it...it's actually worn through different areas of their engine and diff. See http://www.amsoil.com/lit/g2457.pdf for test results. Yes, it's an Amsoil site, but they've got photos and test samples so you can judge for yourself.

Not sure about the others, but with Amsoil, you won't need additive either.
 
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Perfect!

I will be rounding these parts up that I need and have someone put it all together for me as I want to be dang sure it is done right....thanks to all!
 
merkurmadness said:
I went w/royal purple gear lube it already has the additive and ended up costing a few bucks less than lube and additive. I've put a few thousand miles on the posi/gears works perfect!
Click to expand...

Hope you changed your fluid at 500 miles! The new gears have a metal coating on them and it contaminates the fluid.
 
Probably will just go with FoMoCo for the gear oil. :big-grin:

I got a rebuilt TracLoc carrier for 82.00 buck's, and a set of Ford 3.73 gears with only 3500 miles on them for $67.
Next I will get the rebuild kit, and the axle bearings/seals.

I know the Tracloc carrier is a Ford and plan to use it whether if it's a IRS unit or not....But how do you tell what it is?? I noticed that some carriers were more rounded than others on one end, and thats the one I bought.

Does anyone know where online I could find all the spec's for these ford 8.8's ?
It's not that I don't trust the re builder..just would like to get a heads up and learn a little somethin somthin..:eek:
 
I've said it before. Balance YOUR shaft and replace the U-joints.....it will be good.
 
You can tell the difference between the IRS and non-IRS differentials by the spyder gears where the halfshafts spline into. On the IRS units the inside edge of the spyder gear is beveled while on the non-IRS unit it is a square step on the inside edge.
 
Ok....so what is the best way to get it out? Drop the tank? Will the exhaust be in the way too? Can it come out the back when the rear diff is out?
 
Just wanted to throw out a picture of this carrier I bought..I see a bevel inside but wanted to see if anyone can tell me if this unit is IRS or not?
I just pulled out the rear-dif today by myself...not so bad, it took around two hours.
Monday I will be taking it to be rebuilt with 3.73s and the trac-loc.:cool:

000_2401.jpg
 
Hard to tell from that pic, but you're looking for a bevel on the splines on the inboard side of the spyder gears near the crosspin.

Here's a pic from TCCoA...

sg5.jpg
 
Yep, that's a non IRS unit.

No biggie though. Simplest is to leave the circlip off the halfshaft. Or you can have the side gears machined. At one time you could buy the side gears and replace them, that may be worth investigating.
 
I installed a used gearset but I did change the lube but it was closer to 1000 miles(1 weeks commuting) just to see if everything was ok. (I had a slight humm on decelleration which has since quit.)I now have over 5000 miles and I wish I had rebuilt the trac-loc its working but the left side is stronger than the right( backwards from the 8"-9" rears I'm used to!)
 
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