hiluxury

OK so I bought a Detroit TruTrac off a guy in my neighborhood. He was going to put it in his rig, but got an elocker instead. The thing looks absolutely brand new, clean and shiny.

He never ran it, but says it came out of the FRONT of an 8" Yota. I want to run it in the back, which means I would need to flip the gears.

So I read the following:

http://www.discoweb.org/truetracgears/index.htm

OK, using his naming scheme (the ring gear end of the Truetrac is the "bottom") he says that "if the gears rotate CLOCKWISE on the top end of the carrier (when removing them), it’s a REAR Truetrac". When I pull out the center gear it goes up and clockwise. So according to this info, it should already be setup to be a REAR.

The guy on that page is working with a Land Rover Disco, so I am wondering if the Disco is reversed from Toyota?

Hoping someone knows the answer, or can tell me how to figure it out. Clearly the teeth are designed to drive in one direction or the other, but I don't know which way.

The number '50874 02E04' is scratched on the side of the carrier - serial number? Google came up with nothing on it. It also has '0865' punched into the top and bottom caps. Dunno what that means.

Thanks for any help.

-Josh

waskillywabbit

iTrader: (-1)

Contact Detroit TruTrac techline Monday. Pretty hard to tell what you have with no pictures either.

So is the locker setup already in a diff or its still just loose needing to be installed?

:wabbit2:

Tofer

A Toyota 8" 3rd is a toyota 8" 3rd... It doesn't matter front or back. Throw it in your 3rd and call it a day.

4Crawler

iTrader: (3)

Except for the TTs, they have the internal torsen gears set up for forward or reverse rotation. I think it has to do with the torque biasing, a rear TT is set up to bias more torque in the forward direction (and thus less in reverse) and the opposite when they are set up for the front. So while a front TT would work in the rear axle, swapping those internal gears would make it work better.

hiluxury

The Trutrac is not installed... its sitting here on the table next to me

It looks exactly like the one in the pictures here:

http://www.discoweb.org/truetracgears/index.htm

Just FYI, I found this cool animation of how the TT works:

http://www.youtube.com/watch?v=2fTYlGayCbk

You can see in the video that when the wheels are spinning at different rates, the pinion gears in the TT get forced against the inside of the carrier, and that is where the bias comes from. At 1:25 in that video, they show the gears spinning and you can see the outline of the carrier. I held mine up in the exact same orientation, and my gears are set up the same way. I'm thinking this thing is already set up for the rear.

I guess if no one else chimes in, I will give Eaton a ring next week to be sure.

Thanks.

-Josh

hiluxury

Update: talked to Eaton. They confirmed that the part number is for a Toyota 8" Front. They would NOT tell me anything about how the gears should be oriented - said they are not supposed to give out that info. They said it would work either way, but is stronger in one direction.

They also told me (several times in no uncertain terms) NOT to take it apart. They said it takes an engineer to put it back together properly, but that I might get lucky.

So given that it IS a front unit, and it came out of the front of a truck I am thinking I should flip the gears. This means the info on that Disco website is either WRONG, or there is some fundamental difference between a Toyota vs. Land Rover gears.

I would love to hear from anyone who might know for sure!

Thanks.

-Josh

JamesD

Talk to this man because he is the best of the best: http://www.gearinstalls.com/index.htm His name on here is Zuk as well. He will give you the low down on what to do. I would HIGHLY recommend him to do the install if you do not know how to do it but if you read his installs you can get some neat "how-to's" and tricks of the trade.

James

hiluxury

Thanks James... I just received the same answer ("ask Zuk") from another source within about 1 min of your post

His web page seems to indicate he is not doing installs, but I will ask.

I will post back any info I find out. Hopefully will help someone else out down the road.

Thanks.

-Josh

drew303

When i bought my TrueTrac about 4 or 5 yrs ago there was no descriptive words, like front or rear application. Simply Toy 8" Truetrac. This is the first I've heard that theres a difference between the two applicatioins.

If there is, thats cool but I still don't care. LoL

I ran the TT in the rear for 4 yrs and it's been up front for 1 and performs great never one problem.

So messing with it at all I think is a bad idea. It's not gonna perform any miracles in the rear no matter what you do to it.

waskillywabbit

iTrader: (-1)

Zuk takes extended fishing trips I think during the year.

:wabbit2:

ZUK

iTrader: (1)

ha! You got that right waskillywabbit. Actually, it looks like I changed my plans for this winter....no planned installs but the site will always be up for reference.
So I'm curious what Josh finds out with what I am having him do to figure out that rear TT.
ZUK

PS--Josh-- Just an idea....If you could change the name of your thread to Flipping Truetrac Gears then this thread might come up near the top of the search results when others google it.

hiluxury

Title changed. And thank you for your help!

dropzone

iTrader: (6)

hmmmm. you can't change a thread title, you only changed the post title.

Per Master Zuk's request I will change it for you.

I still find it hard to believe that they list it for a Toyota front only but am willing to be educated

hiluxury

Thank you Super Moderator, Sir, may I have another

We have determined that my TruTrac is a rear, contrary to Eaton's part number.

The info on the discoweb.org link that I posted seems to be correct.

Robb, there definitely is a difference between front and rear. The front and rear have different part numbers (Rear is DTL-913A611, front is DTL-913A609). The difference between them is the orientation of the gears.

If you want more gory details, take a look at this:

http://forums.hybridz.org/index.php/...s/page__st__20

Checkout the post by "JMortensen" about halfway down the page.

So all you future flippers, go with the discoweb.org info. Now to go pull the 3rd and get on with the install.

Thanks guys!

-Josh

ZUK

iTrader: (1)

Thanks Robb Josh and I concluded that his was already set up for a rear application....take note of the spiral direction on the helical outer gear. I never really realized it but alot of the torque bias is derived from the 3 little helical gears being pushed outwards up against the case itself....it's a frictional traction grabber. Seems like some of the old, high mileage Truetracs would have egg shaped holes with that wear Josh verified the extra friction by placing the sidegear in the center and noting that it took more effort to rotate the sidegear(by hand) in the CCW direction as compared to the CW direction. ZUK

dropzone

iTrader: (6)

Wow, learned a lot about that, pretty cool
Thanks Zuk. Off topic, Zuk, but how goes Fab32?

ZUK

iTrader: (1)

Fab32 I'm the network guy that gets to take my Fluke Onetouch sniffer, as needed, and figure out why the F32 tool just lost comm. Most of the time, it's just a matter of resetting the port that shutdown perhaps due to security. F32 is ramping up nicely and so is the extension on the side of the main building.

I just googled the topic and this thread is #2....right below the article on actually flipping the gears...cool.

ZUK

iTrader: (1)

Here's something else I found interesting.....here's the center section that's is under some pre-load tension between the 2 sidegears(center gears)....


As the truck accelerates forward the sidegear is forced down onto this matching surface in the pic above....the spring loaded "curved" washers cushions the harshness of the engagement. So the TT works on 2 different
frictional surfaces and it is all about friction on the TT units. The 3 outer helical gears scrub and ride against the outer case and the sidegear is forced down harder on to the washers to act like a small diameter 1 plate clutch type posi(frictional).

Hey Josh....did you notice when you had the sidegear in there and turned it CCW that the 3 helicals tried to walk out of the holes?

ZUK

iTrader: (1)

And one last thing.....the inter-action between the left tire and right tire.....the helicals on both sides are in mesh with each other as shown in the pic below. So, if the other set of gears is in motin...or standing still will help with the traction. That's all I have to say. I'll let someone else get a word in now ZUK

hiluxury

Hey ZUK,

No, I did not notice the 3 pinion gears trying to walk out of the case. I think their engagement with the gears on the other side tends to keep them in place. Will give them another spin tonight when I get home just to confirm.

There is a LOT of talk about the washers / preload in that other thread you sent me.

Its a pretty ingenious design. I too would love to see the insides of one of these things with about 50K on it... I bet you would see some very noticeable wear. Traction via gears grinding away at the insides of the carrier! I can see now why they say not to use synthetic gear oil... if you don't have friction the thing will not work.

-Josh