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Old 07-01-2022, 12:52 PM
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Default Differential question

I have a new Strange center section installed in a car, and I can't remember whether I went with their 31 spline clutch differential or TrueTrack. I bought it in 2016 and have no invoice and the vendor records don't go back that far. I only thought about this because I have to decide whether to add friction modifier--Strange says not to use friction modifier with TrueTrack...but needed with the clutch style. Is there a way to tell what I have without pulling the center section?

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Old 07-01-2022, 02:22 PM
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If it has one of those big fill caps you can probably get a flexible borescope tool in there and look and see. Harbor freight has some inexpensive ones if you don't have one.

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Old 07-01-2022, 02:29 PM
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I've noticed with the true tracs that when the car is in the air and I spin one tire, the other tire doesn't necessarily follow it exactly like a clutch style posi unit does.
Sometimes it even spins opposite of what I'm spinning the other tire.

I'd like to put eye's on it to be sure like Scott said but this might give a clue.

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Old 07-01-2022, 03:03 PM
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could you ask strange if they normally put a tag on the housing like GM used to do, to indicate whether the additive was required? if so, the absence of such a tag would suggest you have a truetrac. if not, the absence of such a tag tells you nothing.

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Old 07-01-2022, 03:15 PM
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If worst comes to worse, Refill it without the modifier.
If it chatters then add it.
Having chatter will not harm the rear for a couple of spins around the block.

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Old 07-01-2022, 03:22 PM
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The modifier won’t affect the Truetrac so if add modifier you will be covered either way.

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Old 07-01-2022, 06:35 PM
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The instructions that came with my True Trac says to use the lubricant specified by the vehicle manufacturer. This is ambiguous as my open diff required no modifier, but I could have ordered a posi which requires a modifier. I don't know who I talked to or how I got the info that the True Trac should not have the modifier added. It makes the oil slippier. Because the True Trac is a helical gear system it requires a bit of friction to operate properly.
Both tires in the air, sometimes sometimes they spun like a posi, sometimes like an open. On the street - two equal black strips.

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Old 07-01-2022, 07:21 PM
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Quote:
Originally Posted by 25stevem View Post
If worst comes to worse, Refill it without the modifier.
If it chatters then add it.
Having chatter will not harm the rear for a couple of spins around the block.
I thought about doing this, but it's been sitting for 6 years and might not be able to distinguish chatter from noise that's likely from stuff being dried out.

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Old 07-01-2022, 07:24 PM
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I'm no expert but this looks like a clutch style differential and not a TrueTrac. Can anyone confirm from this photo?

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Old 07-01-2022, 07:29 PM
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I can't. On GM clutch style, you can generally see a tab from the friction plate sticking up if I remember correctly. I think you can see the grid looking pattern on the tabs.

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Old 07-02-2022, 05:06 AM
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The True Trac is a worm gear system or spin-off of the Torsen design. It isn't going to care one way or the other what type of lubricant you use.

I'd put the additive in the gear oil and go on to worry about something else.

A couple more comments about the Torsen design. They are fully mechanical and eliminate the spider/side gears. When you have the vehicle jacked up turning one wheel without trying to hold the other it may act somewhat like an open diff so it is often difficult to tell if one is being used without pulling the cover to take a look.

This vehicle explains the parts used and how they function.

https://www.youtube.com/watch?v=JEiSTzK-A2A

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Old 07-02-2022, 10:27 AM
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Here is the Eaton Truetrac video .
https://www.youtube.com/watch?v=lZmsY2YvVsc

The six bolt heads on each end could be used to identify it.
My truetrac came with an excellent owners manual that covers all of the Eaton diffs.
It specifically recommends mineral based GL5 80w90 gear oil for the truetrac. Synthetic gear oil is not recommended and it also states that friction modifiers should not be used for the truetrac as they will decrease performance (reduce the differential bias ) .

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Old 07-02-2022, 04:47 PM
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Quote:
Originally Posted by Tandyman View Post
My truetrac came with an excellent owners manual that covers all of the Eaton diffs. It specifically recommends mineral based GL5 80w90 gear oil for the truetrac. Synthetic gear oil is not recommended and it also states that friction modifiers should not be used for the truetrac as they will decrease performance (reduce the differential bias ) .
Got the same info with the Eaton TrueTrac in my 9-inch. As you say, the friction modifiers won't hurt it, but they will (in theory) reduce the effectiveness of the limited slip.

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Old 07-02-2022, 05:55 PM
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They may say that, but I don’t believe it since there are no clutches or cones.

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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule.
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