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Changing diffs


Alex Wong1697456877

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Having not thought it out completely, I had a bit of an adventure removing the diff. (Unbolting the A-frame whilst the car is lifted by the de-dion tube is not a good idea!!)

 

Anyway, the A-frame, diff and prop shaft are out now. When I get the diff back, what's the best way of lifting the car and putting it all back in?

 

Alex

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Also,

 

I assume that it's best to put the diff and propshaft in as one. Can this go back in with the de dion tube in situ? Does undoing the radius arms give enough room to wiggle it in? I had to separate the two to get it out, but this is difficult to do with the propshaft trying to rotate all the time.

 

Alex

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Alex,

 

The brakes will allow you to tighten the diff to prop bolts. Just put the whole lot together before you tighten these up and have someone handy to press the brake pedal.

 

They are not that tight 45lb/ft from memory.

 

Do soem press-ups and you'll be able to lift the diff into position by laying on your back with it on your chest.

 

Then get someone else to insert the bolts (coppaslip on the long one helps immensely here)from above with the boot floor removed.

 

Then remove the bolts one at a time and shim out the diff equidistant from the tubes linking fore and aft of the bottom of the wheelarches.

 

Good luck, its a horrible job.

 

 

 

 

Fat Arn

See the R500 eater (happy now Richard??) with a Commagirl astride.....hereid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

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Alex,

 

The shims are there to space the diff within the chassis brackets centrally. Centrally being the crux, failure to get it central will result in vibrations being transmitted through the car. I recon its better to leave the prop in the car thereby doing away with the need to drain the Gbox, just push it forward slightly and tie it up out the way fit the diff then couple up the prop flange. Thats how I did mine. Don`t forget to replace the blue prop flange nuts and to loctite them on assembley

 

Rob.

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Alex,

I put my car on axle stands (under the forward bush of the trailing arms) and then used a trolley jack to lift the diff in to place while inserting the bolts and washers. It is also worth having a long screwdriver or pry bar handy for easing the diff over when inserting the shims. I left the prop connected to the engine and held out the way with string or ty-raps. To do up the prop bolts to the correct torque use the hand-brake to stop the driveshafts turning.

If you need help give me a shout.

 

 

 

 

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I've just discovered that it can be done single handed by bringing your knees up to your chest and balancing the diff on your shins, leaving your hands free to play with the measuring tape, bolts, pliers, screwdrivers, washers and inspection light as required.

 

Not sure that I'd recommend this as the best way of doing it though...

 

Miraz

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I know that its to late to tell you this Alex but for any one else taking there diff out as you pulleach bolt out collect the washer and cable tie them to the coresponding chassis hole then when you come to put the diff back in cut of the washer and lay them out in a sensible order so they all go back on the right bolts then diff goes in the same way it came out.

Sorry if this sounds contrasending.

 

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The Suretrak uses a system of gears (damned clever things, gears) to direct the most drive to the wheel with the most grip. The plate-type simply uses clutch-type plates to limit the amount of slip.

 

One could suppose that theoretically the Suretrak is better since it doesn't interfere with what the diff is actually trying to do under normal cornering circumstances (i.e. allow one wheel to turn faster than the other) whereas the plate-type will always transmit more torque to the slower-turning wheel which tends to encourage understeer.

 

In practice AFAIK all the race boys have switched back to the ZF plate type, AIUI mainly because it doesn't go "open" when one wheel is airborne.

 

I believe that the Quaife torque-sensing diff doesn't go open like the Suretrak (RIP) one does.

 

I'm very happy with my Suretrak.

 

Mike

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The Superlight racers were in the habit of bouncing a wheel in the air over the kerbs. The Suretrak was allowing the airborne wheel to spin up. With >180bhp and big wide slicks, the shock load into the drivetrain when the wheels next made contact with terra firma was stripping the teeth off fifth gear on the six speed gearbox.

 

With the plate diff this won't happpen unless you get both wheels in the air and the shock load will consequently be less to each wheel.

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Help me out here chaps.......stop groaning.....

....AIUI mainly because it doesn't go "open" when one wheel is airborne.

 

How does the unloaded wheel "know" it's airborne. Sureley the diff just sees a wheel with less/more speed/torque, and adjusts accordingly. If it's a question of torque, then at what point does the diff go openquestion.gif It must be possible for the diff to go open before the wheel is airborne. Is it a designed in feature, or a consequence of the design, and unavoidablequestion.gif As it doesn't appear to be a desirable effect, why haven't they improved upon the designquestion.gif

 

And Mike........I did think of some aerodynamic benefit re the diffuser. It stops loads of air getting in the space of the tank/boot/rear body section. It might even reduce rear end lift/drag........slightly..........er...........wink.gif

 

 

 

Edited by - Blatman on 18 Sep 2001 19:56:43

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> I believe that the Quaife torque-sensing diff doesn't go open like the

> Suretrak (RIP) one does.

 

We had a torsen diff (that's the Quaife one isn't it?) in our historic mini cooper last year. When we lifted an inside wheel out of a tight hairpin all the drive went to that wheel and we went nowhere. This year we're running a plate type diff from gripper. We get great drive out of hairpins. Bad news is that it's an absolute nightmare on the straights, pulls like a..... pully thing. Put us in a ditch for a couple of minutes on the only straight over Eppynnt in August.

 

Oh, and if the scrutineers lurking, then yes of course they had torsen diffs in 1967.

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