Defender LSD

[crump]

"The new Detroit truetrac rear axle limited slip diff gives Defender owners another traction option for their vehicle.The unit suits the salibury design 24 spline axle,4.10 and lower number ratios.The detroit trutrack diff stays open until different wheel speed is detected and the faster wheel is braked." Available from OL.

Ok, can anyone explain is this better/worse than air lockers?
Would it work with TC?
What are the pros and cons?
And anything else you think is relevant.
TIA.

[PhilipA]

These are a Torsen type diff, having seen an exploded view, like in a Hummer.
They rely on a mechanical oddity that the centre gear can drive the planetary gear but not vice versa owing to the reverse design of the gears .
A Torsen is the centre diff of a 2002 on Range Rover.
They should be good but do not give 100% lock like a locking diff.
I seem to recall an issue with Hummers that you have to load them up by spinning a wheel while both are on the ground or they do not lock a wheel in the air( like most LSDs).
To me that negates the main benefit of a locking diff.
But hey are automatic like a detroit locker so do not need driver intervention
Regards Philip A

[rick130]

can't remember the bias ratio of the tru-trac, but being a worm gear design it won't drive if a wheel is lifted. You need a small amount of traction, even if it is slippery mud to bias. If you can lightly use the brake while the wheel is in the air it will bias the torque back across.
As Philip said, it works similarly to a Torsen or Quaife ATB (which is based on the original Torsen design)
It would actually work really well with TC, as Sam Overton has found out when testing the Haultech TC system. The Haultech boys used a pair of tru-tracs in one of their test vehicles (the buggy ??) I remember him saying in a thread on OL that in his opinion it was almost as capable as being fully locked while being much kinder to the driveline

BTW, the tru-trac has been around since the mid seventies. I well remember reading about it in (US) Off Road and Four Wheeler as a kid.

[rick130]

website of the Aussie importer http://www.locked-drive.com.au/index.html
looks like tractech (who made the tru-trac and Detroit Locker) has been taken over by Eaton.
Here's the US website for the tru trac http://www.detroitlocker.com/DT.htm
http://www.detroitlocker.com/images/DTT-Exploded-700pix.jpg

[Slunnie]

The folk in the US having been using the torsen type diffs (Tru-trac) in the Disco2 for years. Apparently with ETC they are just brilliant and silky smooth. The locker component - well, locked is hard to beat if needed.

[JDNSW]

(snip)

BTW, the tru-trac has been around since the mid seventies. I well remember reading about it in (US) Off Road and Four Wheeler as a kid.

A quick check confirms my memory that this differential is described in my "Automobile Engineering" published in 1926 albeit with different details and name (M& S or Brown-Lipe-Chapman). So it has been around a long time, although possibly not with that manufacturer.

The bias ratio depends on the angle of the gears.

As far as results go, this would seem to be a much better type than either a conventional or locking differential, but they are much more expensive to build, and you have to wonder about reliability and durability with all the extra bits, although I suppose this depends on how well they are designed and made.

John

[rick130]

John, yes the original design has been around a looong time, a brief history was given somewhere in one of my race car engineering books and it was invented by a Mr Gleasman in the twenties. Back then the metallurgy available defeated them re reliability. With modern metalurgy and oils they appear to be very reliable.
The Torsen diff is made by Zexel-Gleason and it's used in lots of high performance cars from Europe and Japan. The Quaife ATB diff is used in some RS Cosworth things in Europe as well as race cars and Land Rovers. Quaiffe even have one to replace the centre diff in an LT230.

[Frenchie]

What sort of $$ are they?

[spudboy]

Here's a reply from another thread on a similar topic:

LDS- locked drive systems
granville sydney.
the 2 blokes to talk to are clause and david, owners..

http://www.locked-drive.com.au/ (http://www.locked-drive.com.au/)

i bought my front true track and rear detroit from them this month! bout $980 front and $1100 rear.

opp lock wanted $1600 and $1400:twisted:

[p38arover]

"...4.10 and lower number ratios

Not much chop for standard vehicles. We'd need a higher ratio of 3.54:1

I think 4.10:1 would be too low a ratio for general road use on standard tyres.

With this, you'd need to do the front as well and would only suit cars with bigger tyres or those that are into rock climbing.


Ron

[Blknight.aus]

this is similar to the 1st/2nd gears used in some auto boxes to achieve reduction. Ive driven a vehicle with them but you must have some restrictive effort to both wheels for them to work and then there is a ruling that depends on the gearing as to how much drive you get. Say you have one that gives a 2:1 advantage if one wheel at a given rpm can provide 100nm of tractive effort then the other wheel will be driven at 200nm tractive effort at half the rpm's. Its a little more complicated than that but I believe thats the concept. From the look of the picture they are taking advantage of compund epicyclic gearing by using the pinion to drive both sets ring gear having the suns driven and letting the planets walk against each other during diff operation.

In most non 4x4 situations its enough to keep you moving but I wouldnt want to be depending on it cross country, as soon as one wheel leaves the ground thats all she wrote.

[discowhite]

In most non 4x4 situations its enough to keep you moving but I wouldnt want to be depending on it cross country, as soon as one wheel leaves the ground thats all she wrote.

bzzzzzt wrong!
ive got vdo and first hand experiance that with a wheel off the ground the true track DOSE still drive! farrels road, watagans and appin steps.
also now my traction controll hardly ever kicks in!

cheers phil

[stevo]

I broke a axle on the front awhile ago the left hand wheel was in the air I was pulsing the brake pedal to get the drive across when bang the axle snapped inside the cv stuffed that as well the traction control was off at the time and I have had the tru trac fitted for awhile now

[DirtyDawg]

What sort of $$ are they?

Front true trac $900 rear "No Spin" $890 plus GST and 3% for credit cards;)

[Bush65]

Not much chop for standard vehicles. We'd need a higher ratio of 3.54:1

I think 4.10:1 would be too low a ratio for general road use on standard tyres.

With this, you'd need to do the front as well and would only suit cars with bigger tyres or those that are into rock climbing.


Ron
Aren't you referring to the final drive gearing?

This has nothing to do with a true trac. Your existing crownwheel bolts to the true trac and does not affect the gear ratio.

[justinc]

I'm fitting front and rear tru tracs to a disco 1 this week, will post up after the test track is visited....

JC

[LandyAndy]

Hi Nigel
Where did you get those prices????,sound pretty good.
Andrew