zilspeed
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| posted on 27/7/08 at 01:31 PM |
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Been researching choices of diff.
First choice was going to be something which originally was used in RWD config, which meant Sierra probably.
But there's no real supply of those left.
For the point of view of suitable output flanges, It seems that anything with bolt on cv joints in a FWD transaxle might be suitable. Remember,
we're chucking away everything except the bare diff and output shafts.
So, first observations of suitable donor boxes.
VW Golf MK2 / MK3.
Anything else ?
Trying to come up with easily available choices here.
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adithorp
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| posted on 27/7/08 at 04:08 PM |
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OK, I'm going to say this one final time. IT WON'T WORK! It will with a diff lock (not lsd).
Theres a simple (if dodgy) way to try it. Jack up one rear wheel with a trolly jack on a flat, hard floor, so that the car and jack is free to roll
forward on 3 wheels and the jack (the dodgy bit). Now leave the car in neutral so the diff cage is free to rotate. Now turn the lifted wheel (your
input shaft) and see if the diff drives the other wheel forward (your output shaft).
Guess what... IT DOESN'T WORK! The prop shaft spins (driven by the spining cage) and thats where the power goes; Into the spining cage...and
without the input flange and gears it'll have less weight to drive.
adrian
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Bob C
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| posted on 27/7/08 at 05:43 PM |
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'fraid Adrian's right zil, dunno how to explain further - there are 3 things, cage & 2 output shafts all geared together & if you
let go of any one there is no torque on any other. The power doesn't go anywhere, there is no power because there is no torque
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mark chandler
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| posted on 27/7/08 at 06:16 PM |
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It will work, the range rover diff does this already.
So jack up one side of a range rover, diff lock out car in gear engine off, the external part of th Xfer diff is now locked solid as the gears from
the engine are meshed, turn a front wheel forward and the rear will spin backwards (planet gears in Xfer diff reverse the rotation).
Now take the car out of gear and engage diff lock, essentially jamming the xfer diff planet gears, now when you turn the front wheel forwards the rear
also goes forward the whole xfer diff is spinning.
Stick the car in gear and its all wedged against the engine.
Regards Mark
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adithorp
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| posted on 27/7/08 at 06:29 PM |
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I did say it would work with a diff lock and I like the idea of a transmission lock thrown in as Bob surgested.
But it won't work with an open diff as Zil is proposing.
adrian
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zilspeed
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| posted on 27/7/08 at 06:47 PM |
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And you're absolutely right Adi - I do have my head around it now.
I'm definitely glad we have had the discussion.
So, as Mark says, use an already available locking diff.
Or, devise a method for locking an existing diff for direct drive.
Thanks for all input so far lads, it has helped me to understand things more clearly.
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paulf
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| posted on 27/7/08 at 09:26 PM |
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This is something I also once considered and came to the conclusion it wouldnt work when I had the car jacked up and turned the wheel in gear and in
neutral .
The 4x4 diff sounds feasible but I think the problem would be lubrication as this was the main fault with early reverse boxes as they contained so
little oil it soon overheated.
I had considered trying to dismantle an auto box and see if it is possible to use some of the sun and planet gears from it.
Paul.
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zilspeed
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| posted on 30/7/08 at 05:13 PM |
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I think I may have it sussed.
The diff needs to be a locker to provide forward drive.
Ideally it will be already in a housing which can be modified to suit.
It should be robust to prevent overheating.
The diff we need is from the 2nd generation of the Audi Quattro system.
That;s the manually lockable diff from everything up to the mid 90s.
Currently searching ebay Germany.
I believe that this diff will give us forward drive and reverse drive.
Keep watching 
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zilspeed
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| posted on 9/8/08 at 10:39 AM |
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What Marck Chandler said about a fornight ago, further up the thread.
He's dead right, no question about it.
Ignore anything else I may have said about Audi diffs etc. Way too big and cumbersome. Don't ask me how I know....
Anyway, Landy centre diff is already meant to live in the tranny tunnel and can handle the torque of a V8 crawling over rocks or pulling a horsebox.
Has diff lock for forward drive. Can easily have the cage locked for reverse.
As before, you may or may not choose to keep watching.
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