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1997 thunderbird LX
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350 Posts
Discussion Starter · #1 ·



Hey guys I recently got the control freaks diff cover, looks sturdy as can be.
I have a question tho, in order to rebuild the diff what parts do I need? Been doing some googling and came up with this. Wanted to run it by the gurus on here to get some tips or tricks. I have a 97 tbird but was thinking of hitting the JY to grab a mark diff, axles and maybe the drive shaft.

so far I have this.


I’m assuming it’s just the bearing and clutch packbut not entirely sure since I’ve never rebuild one.
Thanks in advance
 

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1994 Cougar XR7 DOHC/5-Speed
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23,912 Posts
I can’t see what’s in your cart but I bought the bearings and Trac Lok kit from various sources, “kits” gouge the **** out of you, it shouldn’t cost hundreds of dollars for 4 roller bearings and races and a Trac Lok clutch kit. Does your car have traction Lok now, or are you changing ratios? If your not changing gears or adding a new carrier I don’t think it’s worth blowing the diff apart and changing the bearings. You’ll need tools more than anything, drivers for the races, in/lb torque wrench for the pinion preload and dial indicator for backlash are essential, plus marking compound for the gear mesh and ideally a press to get the bearings on/off.

I got this when I rebuilt mine, Koyo bearings are what Ford uses so don’t get too hung up on “Timken or bust”.


The clutch kit is Ford part # 6L1Z 4947 B. Shop around, I found mine for $62 delivered. Comes with clutches steels and shims. These are the paper ones but IMO Carbon fiber clutches a waste of money.

The only Mark worth grabbing the driveshaft from is the 93 one piece.
 

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1997 thunderbird LX
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350 Posts
Discussion Starter · #3 ·
I can’t see what’s in your cart but I bought the bearings and Trac Lok kit from various sources, “kits” gouge the **** out of you, it shouldn’t cost hundreds of dollars for 4 roller bearings and races and a Trac Lok clutch kit. Does your car have traction Lok now, or are you changing ratios? If your not changing gears or adding a new carrier I don’t think it’s worth blowing the diff apart and changing the bearings. You’ll need tools more than anything, drivers for the races, in/lb torque wrench for the pinion preload and dial indicator for backlash are essential, plus marking compound for the gear mesh and ideally a press to get the bearings on/off.

I got this when I rebuilt mine, Koyo bearings are what Ford uses so don’t get too hung up on “Timken or bust”.

[/URL]

The clutch kit is Ford part # 6L1Z 4947 B. Shop around, I found mine for $62 delivered. Comes with clutches steels and shims. These are the paper ones but IMO Carbon fiber clutches a waste of money.

The only Mark worth grabbing the driveshaft from is the 93 one piece.
Cheap ass link this is what’s in the cart



my car currently has 3.27 and does have traclock. Not looking to change gear either. I’m mainly wanting a rebuild because I feel the diff isn’t locking completely when I’m trying to get a lil sideways, it takes some convincing to lock up. Car has 140k miles and I’m sure it’s time for a refresh.

The carbon clutches are almost 200$! But from what I’m reading the terminator cobra came with those stock. I’m not gonna be putting anywhere near that torque through it any time soon so it’s not high on my list.
As far as the shaft, I know the 93 is a legit 1 piece but even the newer 2 piece shafts be better than the steel thunderbird one? The JY has em pretty cheap so I wouldn’t mind it.
 

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1994 Cougar XR7 DOHC/5-Speed
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I’d just do the trac lok rebuild and halfshaft seals only to the existing iron case then, it’s not worth replacing the pinion and carrier bearings for the minuscule weight savings of an aluminum case and existing gears

Take out the axle brearings, that’s for solid axles at the brake end, for IRS the equivalent would be the halfshaft seals and bearings Ford Performance Mustang 8.8-Inch Rear Axle Bearing and Seal Kit; IRS M-4413-A (99-04 Mustang Cobra) - Free Shipping


Ford performance is marked up from regular ford, you can definitely get that exact clutch kit cheaper by 30-40 bucks.


the two piece mark shaft really isn’t any better than the crimped steel, both have lower critical speed than a true one piece and it can’t be improved. For the effort of pulling it and putting it in in these cars it’s not worth using anything less than a 93 shaft
 

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If you want more grip out of your trac-lock without buying the expensive carbon clutches, you can change the order of the friction/steel pack. From the factory, it is SFSFSFS. Instead, you can stack it FSFSFSF. The outer friction plates will grip on the machined case and the machined face of the spider gear, giving you about 30% more friction compared to the factory stacking. Just re-use the best 2 clutches from your old set along with the ones from the new set.
 

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1997 thunderbird LX
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350 Posts
Discussion Starter · #6 ·
@XR7-4.6 so with both of those links you provided I should be able to rebuild my current pumpkin? 93’s are a lil harder to come by but I feel like it’ll be worth the wait dollar for dollar. How do I know it’s actually one piece??

@MadMikeyL Nice! I’ve heard about this mod but never knew how to go about it. Them damn CF packs are double the price! Is that really how easy it is?? Stack them different? Also I’ve heard something about putting the f150 s spring instead of our stocker, it somehow applies more pressure I guess.
 

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1994 Cougar XR7 DOHC/5-Speed
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@XR7-4.6 so with both of those links you provided I should be able to rebuild my current pumpkin? 93’s are a lil harder to come by but I feel like it’ll be worth the wait dollar for dollar. How do I know it’s actually one piece??
The three links I posted in this will do the whole thing, the 8.8 rebuild kit a few posts up has carrier and pinion bearings/races. Like I said though, I wouldn’t bother with those unless you did do a gear change, or unless your pinion seal is leaking anyway

if it’s a 93 it’s one piece, check the vin. On the shaft it’s obvious, there will be a rubber seam at the end whereas solid is just all aluminum.

@MadMikeyL Nice! I’ve heard about this mod but never knew how to go about it. Them damn CF packs are double the price! Is that really how easy it is?? Stack them different? Also I’ve heard something about putting the f150 s spring instead of our stocker, it somehow applies more pressure I guess.
Other alternative if all your old clutches are toast is to use the thickest shims in the kit and use less friction modifier than specified. Don’t use the F150 S spring, it’s a ***** to install in 28 spline carriers and it doesn’t actually affect the traction lok operation whatsoever. The spider gears force the side gears to spread, pushing against the clutches, the S spring is only there to preload them for initial grip in wet conditions, but a spring doesn’t even actually need to be installed at all for proper operation, some people even swear by running without one for road racing.
 

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I don’t buy the F150 spring mod. The truck spring is wider than the car one, but that is because the opening in the carrier is wider on the trucks. Shoving the F150 spring in place is quite difficult, and it definitely will put more preload on the clutches, but the way a clutch type limited slip works is that when one tire spins under power, the movement of the spider gears creates an outward force that pushes them into the clutches. The spring is really just to keep them preloaded to avoid chatter. Using the F150 spring is only going to cause the clutches to wear out faster under normal driving and turning, but not give you any benefit when the limited slip is actually needed.
 

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1994 Cougar XR7 DOHC/5-Speed
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With 140k and no apparent other problems(noises) besides the trac lok being worn out the the stock bearings should have no problem lasting another 100k with some fresh fluid. Rebuilding the Trac lok only is very DIY friendly with the 3.27 ring gear giving ample clearance for the side gear/clutch stacks to be R&R'd from the carrier without further disassembly
 

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1997 thunderbird LX
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350 Posts
Discussion Starter · #11 ·
@XR7-4.6 essentially if I were to rebuild the traclock all I have to do is replace the clutch packs? Along with doing the alternative stack pattern, that’s all that’s required to rebuild on the cheap? Sorry for all the questions I’m a rookie when it comes to the diff 😬
 

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Just to be clear - the alternate stack pattern + extra clutch will wear out the Trac-lok faster, correct?

That was the answer I got from RobertP a few years ago when I inquired about it.

A stocker is good for 90k miles max. That's the mileage our Crown Vic had when it only would leave the right tire mark on a burnout. It still felt like the left tire was helping, just not enough to leave a mark.

Al
 

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How fast it wears really depends on your driving. Lots of turns will wear it faster whereas straight highway driving won't wear it at all since the spider gears aren't turning relative to one another when going straight. However I really can't see how it would wear faster with the alternative stack pattern. With the F150 S-spring, I could definitely see that wearing out faster since it puts more of a pre-load on all the clutches, but the alternate stack pattern shouldn't make any difference in the life of the trac-lock. If anything, it should extend the life because the load is being shared by more clutches, so for it to not work anymore, you have to wear out 4 clutches instead of 3.
 

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I think he was referring to the wear coming from the extra clutch disc, it was mentioned above that it provides 30% more friction?

Probably irrelevant as it would still take 20 years to wear it out for most people.

Al
 

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Most people, yes. But I remember mikey running a cooler on their lemons car. :)
 

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1994 Cougar XR7 DOHC/5-Speed
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23,912 Posts
I think he was referring to the wear coming from the extra clutch disc, it was mentioned above that it provides 30% more friction?

Probably irrelevant as it would still take 20 years to wear it out for most people.

Al
More friction when it’s under load, as Mike said driving style is what really impacts it, powering through turns is what makes the spider gears “push” on the side gears that engages the clutches. Coasting through turns otoh the spiders are barely under any load(like an open diff) and the only pressure on the clutch packs is the S spring (which stock or even F150 does not provide near enough force by itself to lock the diff)and the friction modifier cuts that preload friction way down, which translates to less wear. With the alternate stack, at least in theory, the extra clutches are distributing the friction across a greater area for the same loads, so there may well be a little less wear on the clutches when compared to the stock stack.
 

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Most people, yes. But I remember mikey running a cooler on their lemons car. :)
Yup,good times!

Try as I might though, I can’t beat on the car hard enough on the street to need that.
 
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