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Unread 02-08-2008, 11:52 AM   #1
VTZJ
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Is there a Truetrac fitment for Dana 35c?

So I went to order a Truetrac for both my front and rear axles today, and was told by the retailer that there is no Truetrac application for my rear, a 1996 Dana 35c. Reason: too much endplay in the axles due to a 0.030 difference in cross pin diameter. Solution: custom machine work or sleeve. Ouch.

Question: Is this info correct? If you have successfully installed and operated a Truetrac in a 1996 or later ZJ, would you please tell me how it went and if possible what Truetrac model number you used?

Front Dana 30 does not seem to be a problem, but comment on this too if you have exp.

Thx.

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Unread 02-08-2008, 12:57 PM   #2
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What does the cross pin diameter has to do with truetrac?!
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Unread 02-11-2008, 06:51 AM   #3
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Quote:
Originally Posted by mendelmax View Post
What does the cross pin diameter has to do with truetrac?!
That's what I said, but then, if I knew the answer to this, I wouldn't be asking for help.

So, are you just posing a question, or are you saying there is no cross pin in the Truetrac Dana 35c application?
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Unread 02-11-2008, 06:56 AM   #4
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I may be making some language mistake (I'm not a native English speaker), but from what I know, cross pin is the pin that holds the spider gears on their place. With truetrac you replace whole carrier, and there is no such thing as a cross pin, because the spider gears (worm gears) have rotation axis horizontally. TT is also c-clip ready as producer states, so I see no reason why it wouldn't work- they probably made it to fit as OEM. I know few people that run TT in their rear D35c and noone mentioned about any problems. Just plug&play.

Maybe your retailer was thinking about lock-right or something like that? With lunchbox lockers indeed, the cross pin diameter is very important.
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Unread 02-11-2008, 07:06 AM   #5
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Originally Posted by mendelmax View Post
Maybe your retailer was thinking about lock-right or something like that? With lunchbox lockers indeed, the cross pin diameter is very important.
Yeah that what I was thinking. Maybe they are confused?
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Unread 02-11-2008, 07:40 AM   #6
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Quote:
Originally Posted by mendelmax View Post
I may be making some language mistake (I'm not a native English speaker), but from what I know, cross pin is the pin that holds the spider gears on their place. With truetrac you replace whole carrier, and there is no such thing as a cross pin, because the spider gears (worm gears) have rotation axis horizontally. TT is also c-clip ready as producer states, so I see no reason why it wouldn't work- they probably made it to fit as OEM. I know few people that run TT in their rear D35c and noone mentioned about any problems. Just plug&play.

Maybe your retailer was thinking about lock-right or something like that? With lunchbox lockers indeed, the cross pin diameter is very important.
I didn't think the TrueTrac was a full-case locker. I thought it just replaced the spiders and not the carrier itself?
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Unread 02-11-2008, 07:51 AM   #7
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Nah it is a full replacement: http://www.nationaldrivetrain.com/sh...ml/page44.html
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Unread 02-11-2008, 08:57 AM   #8
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Shoulda kept my mouth shut. In that case the cross shaft shouldn't matter.....you could always call and ask Detroit.
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Unread 02-12-2008, 02:14 PM   #9
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Quote:
Originally Posted by mendelmax View Post
...cross pin is the pin that holds the spider gears on their place. With truetrac you replace whole carrier, and there is no such thing as a cross pin, because the spider gears (worm gears) have rotation axis horizontally...
Brilliantly insightful. And wrong.

If you go here http://www.eaton.com/ecm/groups/publ.../ct_128482.pdf
and scroll down to the instructions on installing truetrac in the Dana 35c, you will see that the TrueTrac for Dana 35c does indeed have a cross pin. Call it a dummy cross pin if you like -- it is there to fulfill one of the jobs that the now-missing spider gear cross pin performed. That job is to limit inward linear (co-axial) travel in the axle shafts. The C-clips limit outward travel, but are too sloppy to limit travel in both directions. So truetrac provides this dummy cross pin as a substitute. Now what I am told (by the retailer, not Eaton, mind you) is that the 94 and newer Dana 35 had a slightly larger cross pin than the older model, and the pin provided with the TrueTrac unit was sized for the older cross pin, thus is 0.030 too small, allowing 0.015 too much end play in each axle.

You learn something new every day. Every day that you spend countless hours on the internet trying to track down some arcane engineering fact about a product no one cares about and an axle everyone hates, that is.
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Unread 02-12-2008, 03:37 PM   #10
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That's quite interesting, I haven't thought about it that way. I will ask my friends with truetracs in Poland about it.

On the other hand, considering how much play c-clipped axles have, I find it hard to believe that extra 0.015" may matter

Maybe the best way is to ask guys at Eaton?
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Unread 02-12-2008, 06:49 PM   #11
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I would think that if it's been happening since '94 TrueTrac would have corrected the problem by now
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Unread 02-13-2008, 06:31 AM   #12
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Quote:
Originally Posted by mendelmax View Post
That's quite interesting, I haven't thought about it that way. I will ask my friends with truetracs in Poland about it.

On the other hand, considering how much play c-clipped axles have, I find it hard to believe that extra 0.015" may matter

Maybe the best way is to ask guys at Eaton?
1) Thank you for asking your friends. I appreciate your help, and would be very interested in any comments from your friends regarding the Truetrac (end play issue, performance, durability, capability). ZJ is my daily driver, and a family vehicle, in a snowy, icy, muddy region of the US. I need more traction both on and off road, but it must be well-mannered on the highway (so no lockers for me).

2) Good hypothesis about the extra play not mattering. However, I do wonder if it would affect the warranty from TrueTrac if I install it in an application not recommended by Eaton. Also, I'm no engineer, but seems to me that too much linear travel will, at some point, place bad thrust loads on the wheel bearings during cornering, no?

3) I have followed your suggestion and now have a phone call in to a product manager at Eaton, and will try to get some email response from them to post on this forum.

Thanks .
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Last edited by VTZJ; 02-13-2008 at 06:40 AM.. Reason: clarify meaning
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Unread 02-13-2008, 09:41 AM   #13
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Resolved...for now.

Quote:
Originally Posted by mendelmax View Post
Maybe the best way is to ask guys at Eaton?
Done. And here is what Eaton says.

Not all Dana 35c axles have the same cross pin diameter. Older ones were fitted with 0.685" diameter pin. Newer ones fitted with 0.716" diameter pin. Eaton product manager I spoke with says Eaton not sure which vehicles may be equipped with smaller or larger pins, so doen't claim that ZJ has this issue. May or may not.

Nevertheless, Eaton does specify TrueTrac model 912A569 for Dana 35c. THis model does come with a cross pin sized to replace the older, smaller diameter cross pin. Recommends that upon set up installer measure axle end play and if determined to be excessive, remedy by building up end of axles slightly.
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Unread 02-13-2008, 10:03 AM   #14
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BTW, one thing that crossed my mind- I checked part numbers for axle shafts for various years of ZJ production. The idea is simple- if the axle shafts didn't change it must mean, that either the cross pin doesn't matter for them, OR that the cross pin wasn't changed in ZJ.
And so:
98 ZJ: 4762 194 (right), 4762 195 (left)
97 ZJ: 4762 194 (right), 4762 195 (left)
94-96 ZJ: 4713 192-3 (drum brakes), 4762 194-5 (disc brakes)
93 ZJ: 4713 192-3

So, in other words, to me it sounds they are most likely the same. There is "-5" difference though, the question is, whether it was changed to keep order (there were few part number changes on exactly the same parts in Jeep history) or something really changed. Maybe it's some note about the side of the vehicle, because the parts list for 94-96 don't specify the side.

Now the other thing is that these axles were used both in grand cherokee and cherokee. I doubt that Eaton would loose the market for 96&up XJ and ZJ.

I already posted a question about this on our Polish forum, we'll see what the answer will be
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Unread 02-13-2008, 12:57 PM   #15
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Quote:
Originally Posted by mendelmax View Post
BTW, one thing that crossed my mind- I checked part numbers for axle shafts for various years of ZJ production. The idea is simple- if the axle shafts didn't change it must mean, that either the cross pin doesn't matter for them, OR that the cross pin wasn't changed in ZJ.
You are brilliant. That is a powerful deduction. And so obvious -- after you mention it! But then, should we expect anything less from the land of Joseph Conrad and Stanslaw Lem?
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