Limited slip differential rebuild

[Spider69 16]

Dear all,

I have a 69 mach one, on which I have started a complete differential rebuild some weeks ago.

New parts and CURRIE axles have been ordered and shipped, axle and carrier housing repeinted, ready to be reassembled.

To finalize the operation around the clutch we need to measure the correct clearence for the shim and here we need a Ford Tool T68P-4946-A I guess as shown in the pic enclosed.

But we don't have this tool!!!! Does someone knows if we can work without this tool is there a workaround?

Thanks in advance for your help

[RPM 1,157]

 I'm pretty sure my rear end guy measured that with dial calipers. 

[1969vert 55]

[barnett468 418]

Is that epoxy primer?

In case you don't know this, you will likely have to put some friction modifier in the diff to keep it from intermittently trying to engage the posi in a turn. You can get it from chevy dealers.

 

 

[Spider69 16]

2 hours ago, RPM said:

 I'm pretty sure my rear end guy measured that with dial calipers. 

For sure, but we miss the tool, the shim template to measure if  the clearance is correct and which shim we have to use!!

I could find on Internet this drawing, does someone knows it, is this accurate?

[Spider69 16]

1 hour ago, 1969vert said:

 

Hi,

Thank you for this detailed information.

I have the enclosed pic I took from my book which describes quite well how we have to reassemble each part.

What do you mean with "a few pops"?

I think I have a standard pack , not a performance one.

 

[Spider69 16]

1 hour ago, barnett468 said:

Is that epoxy primer?

In case you don't know this, you will likely have to put some friction modifier in the diff to keep it from intermittently trying to engage the posi in a turn. You can get it from chevy dealers.

 

 

Hi,

Not epoxy primer. I used a first primer to avoid rust after having sanded/blasted carefully all the housings.

Special primer coming from a french provider "restom" and then a special coating for the same vendor.

For sure, I will add  "friction modifier", but we have no Chevy  dealer in France :-), unfortunately

[barnett468 418]

13 minutes ago, Spider69 said:

For sure, I will add  "friction modifier", but we have no Chevy  dealer in France :-), unfortunately

oh, lol.

[1969vert 55]

1 hour ago, Spider69 said:

Hi,

Thank you for this detailed information.

I have the enclosed pic I took from my book which describes quite well how we have to reassemble each part.

What do you mean with "a few pops"?

I think I have a standard pack , not a performance one.

 

the rear will act like a spool a little when it is tighter...popping in the rear during a turn.. other than that all is normal  ..you will be able to hear it and sometimes feel it..

[Spider69 16]

no one able to confirm the dimensions on the pic attached?

[1969_Mach1 333]

As far as oils, double check the oil you use.  Many contain friction modifiers and there is no need to add more.  I use Lucus GL-5 rated gear oil in my OEM Ford Traction-Loc without any additional modifiers and it works fine. 

[barnett468 418]

7 hours ago, Spider69 said:

What do you mean with "a few pops"?

From my previous post:

"...intermittently trying to engage the posi in a turn."

 

When this happens, it can sometimes make a little noise and the car can feel a little jerkey as it engages and disengages, but this is not a "problem", it is just inherent in the design when they are set up tight or sometimes when they have new clutches.

A locker rear end can sound like someone is literally hitting it hard with a sledge hammer in the turns, lol.

 

[Spider69 16]

9 hours ago, barnett468 said:

From my previous post:

"...intermittently trying to engage the posi in a turn."

 

When this happens, it can sometimes make a little noise and the car can feel a little jerkey as it engages and disengages, but this is not a "problem", it is just inherent in the design when they are set up tight or sometimes when they have new clutches.

A locker rear end can sound like someone is literally hitting it hard with a sledge hammer in the turns, lol.

 

OK, I understand, thanks.

If it happens I will not be anxious :-)

[Spider69 16]

12 hours ago, 1969_Mach1 said:

As far as oils, double check the oil you use.  Many contain friction modifiers and there is no need to add more.  I use Lucus GL-5 rated gear oil in my OEM Ford Traction-Loc without any additional modifiers and it works fine. 

I have ordered Additif Red Line LSD Limited Slip Differential.

[barnett468 418]

1 hour ago, Spider69 said:

I have ordered Additif Red Line LSD Limited Slip Differential.

I only use the ford recommended oils.

[Mach1 Driver 528]

On 5/16/2019 at 12:26 PM, barnett468 said:

Is that epoxy primer?

In case you don't know this, you will likely have to put some friction modifier in the diff to keep it from intermittently trying to engage the posi in a turn. You can get it from chevy dealers.

 

I think Barnett was messing with everyone a little bit, but no one took the bait. He knows full well that Posi-Traction is a Chevy option, so as he said, the friction modifier would have to come from Chevy. Ford's version is Trac Lok, so directly above he finally said to only use Ford oils.

Barnett, do you prefer Trac-Lok, to Eaton's True Trac?

[barnett468 418]

5 hours ago, Mach1 Driver said:

I think Barnett was messing with everyone a little bit, but no one took the bait. He knows full well that Posi-Traction is a Chevy option, so as he said, the friction modifier would have to come from Chevy. Ford's version is Trac Lok, so directly above he finally said to only use Ford oils.

Barnett, do you prefer Trac-Lok, to Eaton's True Trac?

nope, wasn't messin with anyone...this time, lol. the chevy friction modifier is actually similar enough to the stuff that ford sells, however, where i am, ford does not carry it but chevy does, but when i have a choice, i use the ford stuff.

 

.

[Spider69 16]

Does someone is able to explain me what means the middle column "remove shims from nominal" on the attached pic?

[rockhouse66 22]

I think that is the preload.  In other words, "nominal" is zero preload and then you remove shims to obtain the required preload.

[Mach1 Driver 528]

There is an Autorestomod four part video series on how to rebuild a Trutrac that may help:

 

[rockhouse66 22]

A Truetrac diff is nothing like a traction lok.  No clutch discs.

[Spider69 16]

It is possible that with news clutch plates we go no clearance at all?

Definitely not easy to unserstand how this works!

[Rsanter 149]

There is a specification for the amount of torque required to slip the clutches in those track loc units

 

many people just guess at it and put it together and hold the two halves together with bolts.

then do the torque test.

if too high torque, thinner shims

if too low torque, thicker shims

 

bob

[Spider69 16]

Thank you for your reply.

I  could find someone who has the right tool to finalize the work.

I will post some pics when the rear axle is reassembled.

 

[ddrane1@cox.net 0]

I know this is an old thread.  Spec on 9" traction loc 100-250lbs/ft ( that is moving torque,  not to get it to break free, which will be a little higher). That's a wide range, depends on weight of car, I set mine at 170 in a 68 mustang.  Go for a higher value for heavier car.