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Old 12-21-2007, 10:02 AM   #1
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I saw an interesting article on AWD back in the 80'*, someone took a std FWD layout, put it in the back with the trans outputs pointing forward and rearward and drove a conventional front and rear axle. The transmission differential became the center diff and with different gearing in the front and rear, provided the tq split.

It sounds intriguing, more for a racing or off road. I think it was rock crawlers who might have come up with this. pretty cool.
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Old 12-21-2007, 10:34 AM   #2
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Sounds interesting.

The buick rendevous have a AWD version of the 4T65. I always wished I could adapt one to my riviera.
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Old 12-21-2007, 12:57 PM   #3
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Quote:
Originally Posted by OLDsman105
Sounds interesting.

The buick rendevous have a AWD version of the 4T65. I always wished I could adapt one to my riviera.
The Versatrak is a big POS. The concept is great, but there is one big flaw: The rear drive is basically a Power Take-off (PTO) that is direct geared off the differential. I bought a Versatrak assembly back in 2002 and proceeded to take it apart. I still have it, maybe I'll use it in something, maybe I'll sell it. But the flaw is it does NOT ustilize a center differential! It is direct drive to the rear. So there must be something else in the rear system to allow for differential axle speeds (f-r split) The way they did it was to make the rear differential part-time based on demand. SOunds great in theory, but does not work very well due to the fact that when it IS engaged, there is no f-r split! What hapens is any req'd slippage occurs at the rear clutches. These units are notorious for going bad. GM built a G8 prototype AWD LS1 car, remember that one? it was a '98 or so. The platform is really easy, the Van or Rendez-vous FWD subframe is a direct swap in a 97-08 W-body. The rear is a complete subframe that was adapted to fi the W-body, so why could it not be adapted to fi the H-body, too? The H-body is more like the vans, we use coil springs, shocks and control arms like the AWD Versatrak. I thought about doing this to my 90 Grand Prix, which is why I bought all the stuff, but I changed my mind when I saw how weak the rear diff is.

Then I found a 1990 Pontiac 6000/SE AWD on Ebay back in 2003. So that'* my next project the first L67 AWD!!!!
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Old 12-22-2007, 05:16 AM   #4
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I can't wait for the first AWD L67! I'm going to go nuts! What would it take to install an additional LSD for the f-r in the AWD 4T65?
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Old 12-22-2007, 11:43 AM   #5
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Is Versatrak electronic?
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Old 12-22-2007, 11:51 AM   #6
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Don't mean to be off topic, but how similar is the unibody of a '96 Park Avenue to a Bonne? I know they're both H bodies. I ask cuz I can possibly get one really cheap in decent shape...
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Old 12-22-2007, 12:09 PM   #7
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Quote:
Originally Posted by radomirthegreat
I can't wait for the first AWD L67! I'm going to go nuts! What would it take to install an additional LSD for the f-r in the AWD 4T65?
The front diff in the 4T65 Versatrak is the same diff as the std -65, the difference is the carrier is longer on the end and has a big helical ring gear welded to it (PTO). The guts are the same and I could build the EP-LSD for it. The rear is something entirely different. it does have the ability to drive both rear wheels under extreme front wheel slippage. SO for a short time, you would be true AWD! But the only time the rear actually drives is when front wheels are spinning, under all other driving conditions, the Versatrak is idle and the vehicle is in FWD mode. That'* why it'* a bogus AWD and a big POS.

Here are some pics of how it works:

Transfer case, notice the front diff planetaries, just like a conventional front diff.

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the huge helical ring gear turns an idle gear...

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...that turns the helical on the tranfer case "input" shaft...

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...with a spiral-bevel gear on the other end...

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that turns the spiral-bevel gear on the "output" shaft.

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The rear driveshaft bolts to the output shaft.

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The driveshaft turns the rear diff pinion gear...

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Which turns the "idle" ring gear. The ring gear is part of the intricate clutch drive system, it is made up of two clutch packs engaged by pressurized oil in the rear diff. It gets [ressure from a gerotor-type pump, acitvated by the PCM when front wheel spin is detected.

So you see, it is a direct drive system, but only under certain curcumstances. It could be used very effectively as a drag racing set-up, but I don't know how much power it could transfer! I do know the AWD G8 was running in the 12'* and blowing out the rear diffs, three to be exact, before GM quit that idea. The thing about it is the transfer case has a ratio of, IIRC, 1.02:1. The front diff is the std. 3.29. The rear diff then would need to be a 3.33 inorder to run without breaking anything. I looked all around for a 3.33 R&P to decide what rearend you'd have to use (ditching the idea of a Versatrak rear diff which, as noted, has a 3.33 ratio.) The only thing I found close was a Ford 8" or 9" 3.25 ratio or the 12-bolt 3.36. You could stagger the tire diameters and get pretty close if not dead on.

I was building a AWD '95 GTP, 3400DOHC, twin turbo. I ditched it two years ago and kept all the good stuff. All this talk has got me wanting to try again on something else... maybe an AWD L67 GTP, but with a live axle in the rear, stock interior, stock appearing. I think someone else built one with a LS motor, not sure who... but it was RWD, not AWD!

I hate when my mind starts working like this, I can;t get anything doen just thinking and planning, planning and thinking. Anyone else have this problem?
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Old 12-22-2007, 12:14 PM   #8
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Looking at that rear diff, GM could just as easily made a conventioanl rear differential and used some type of center viscous coupling to take up slack front-to-rear. That'* what I was going to do. I have a viscous coupler out of an AWD Eclipse 5-speed. It was used as a center split b/t front wheel and rear wheel output in the AWD 5-speed transmission in place of a center diff.
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Old 12-22-2007, 12:31 PM   #9
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Quote:
Originally Posted by F14CRAZY
Don't mean to be off topic, but how similar is the unibody of a '96 Park Avenue to a Bonne? I know they're both H bodies. I ask cuz I can possibly get one really cheap in decent shape...
the bonneville is an H body. the park ave is a C body.

they are almost identical. i believe them to be the same untill the back end.
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Old 12-22-2007, 01:33 PM   #10
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Quote:
Originally Posted by samueljackson
Quote:
Originally Posted by F14CRAZY
Don't mean to be off topic, but how similar is the unibody of a '96 Park Avenue to a Bonne? I know they're both H bodies. I ask cuz I can possibly get one really cheap in decent shape...
the bonneville is an H body. the park ave is a C body.

they are almost identical. i believe them to be the same untill the back end.
The '96 Park is an H body, too. The new-for-'98 Park is a C-body.
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