Guard Transmission 901 TBD Diff

Hi All,

For sale is my Guard Transmission 901 TBD diff. It's had minimal use and is in really nice condition as can be seen in the photos. Everything shown is included so it's output flange to output flange. Last time I spoke to the guys at Guard, they said this is now a special order item which takes 3-4 months to make and had a price tag then of $1995 without the flanges. I'm looking for $1500. The diff is in the UK, so shipping is $120 to the USA and $50 into mainland Europe. Anything else just ask.

Many thanks
David

https://i.imgur.com/bNM0wQu.jpg

https://i.imgur.com/ZUF5lX7.jpg

https://i.imgur.com/5vw3BPe.jpg

https://i.imgur.com/BpNseFD.jpg

https://i.imgur.com/180w5nV.jpg

https://i.imgur.com/5usC6wl.jpg

https://i.imgur.com/kNEwjgp.jpg

https://i.imgur.com/vxYO85H.jpg

Is this for early or late model 901's?

Sorry, I should have said it’s an early one.

Just for my education, is this a limited slip differential?

TBD - stands for Torque Biasing Differential. TBD's use gears instead of clutches like LSD's.

They both provide different attributes.

In a nut shell
LSD - clutches lock the axles together

TBD - the gears make resistance so that the axles semi lock.

Quote:

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Originally Posted by 72targa

Just for my education, is this a limited slip differential?

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Hi Peter,

Here's a good explanation to the way these work https://www.kmpdrivetrain.com/differ...-differential/

The biggest difference between a Plate type diff and a Torsen (or ATB) diff in a 911 is that the Plate style diff still works on coast and provides linked braking to the rear. As it says in the article, these are really nice in a street car as the grip on acceleration is where you'd want it and it's a low maintenance part. The Plate diffs wear and in motorsport get rebuilt every season (probably along with everything else).

I hope that helps,
David

Very useful. Had not run into these before. Interesting technology. I know to use a limited slip differential gear oil in that application. What is used in this differential?

Quote:

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Originally Posted by 72targa

Very useful. Had not run into these before. Interesting technology. I know to use a limited slip differential gear oil in that application. What is used in this differential?

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Because it is a gear driven diff, those windows in the side of the casing allows the gearbox oil into it. The guide for the oil is nothing particularly fancy, just regular premium gearbox oil as recommended manufacturers spec.

Learn something new every day!

Price drop to $1250