Testing a center diff

[RallyRS]

Hi.

I have a Legacy RS 1989 rally car.

Done lots of power mods, but it still lacks in torque. Not sure what else to do without spending lots of money.

Anyway. I seem to have problems on the tight twisty roads and slippy surfaces keeping up with other cars. I not the best driver in the world but I keep the car moving nicely, I don't beleive the car could go much quicker without more grip. I can keep up on more flowing roads. The car just doesn't seem to get a good bite of out of the corner. I just get a mass of wheel spin. No power to the ground.

I have tried to correct problem by changing suspension but no success. I currently have 50 Drummend suspension and I have removed all the sway bars. Springs are 220 in front, 180 in rear. 1mm toe out on front and 4mm toe in on back. Ride height and caster are about as is normal on a old legacy.

Also. I have front and back mechanical LSD diffs.

I beleive it could be a problem with the center diff not working correctly. How would I test the center diff? Also I have spare parts gearboxes around my house, how would I test center diff not in a car to check they are working OK?

Thank you for your comments

Any help in any area of the car on getting the power to the ground would help.

As a side topic. I have 10lb flywheel which I can fit while the gearbox is off. Is a light weight flywheel good in a rally car?

Photos and videos of my car at http://teamfanging.spaces.live.com/

[Legacy777]

To simply test the center diff, jack up the front OR the rear of the car. Put the transmission in first gear & remove the parking brake if the rear end is the one being jacked up.

Next try and turn the wheel that is raised. You may need to have someone hold the opposite tire or wedge something underneath it so it doesn't spin the opposite direction (assuming the LSD isn't 100% locking).

If you can't turn the wheel by hand that would be a very basic test to indicate the center diff may be functioning properly.

If the transmission is in gear, and you follow the steps above, and you can turn the wheel, chances are the center diff may not be good.

[94SS_Canada]

let us know what happens!

Sounds interesting!

[bmxkelowna]

I have removed all the sway bars.

put them back on right now. it will stop body roll which will keep the inside tires planted on the ground having a lot more grip

[ultrasonic]

put them back on right now.

It's pretty common for gravel, dirt, and snow rally guys to run smaller sway bars (sometimes NO swaybars) as compared to street driven or tarmac racing set ups. They don't mind giving up a bit of body roll, and the loose surface driving style tends to take advantage of intentional weight shift, and breaking traction when necessary.

[RallyRS]

No swaybars is alot nicer to drive on gravel. Horrible on tramac tho!!!! But some gravel can be so hard packed it is like tramac to drive on and some swaybars would be good then.

I really need smaller swaybars than standard but these are hard to find. I have played with only the rear one in and only the front one in, but seems to make little body roll difference, I notice a larger difference in under and over steer and weight transfers during braking and cornering.

I try testing my center diff tomorrow night and let you know how I get on.

Thanks for all your comments!

[RallyRS]

Any comments on a lightened flywheel mod? I not sure what to expect.

[Legacy777]

LW flywheel will help with acceleration, but the engine is less forgiving when starting out, and less smooth. Also, rpms will drop faster during shifts, which depending on how fast you shift can be bad, or good......

[RallyRS]

HI. I checked the cetner diff as is above. I takes alot of effort to spin the rear wheels with the front wheel left on the ground. I'm guessing this means the center diff is working ok. But I notice the could spin the rear wheels different direction (person on other wheel spining in other direction) without to much effort. I wonder is rear diff is going??? I brought it 2nd hand, but it had just been serviced and breakouts tuned for rally use. I'm not sure.

I think some swaybars may be needed to increase weight change to rear of car on corner exit. Might also try moving some weight to back of car. Back to the drawing board.... again. Those dam EVOs are too fast!!!

[Legacy777]

Both rear wheels will spin in the same direction on my car with the VLSD ONLY when there isn't any load/resistance. If all four wheels are in the air, they'll spin in the same direction.

Doing the test you did also caused the one rear wheel to spin in the opposite direction.

[RallyRS]

A late update.

I found the problem to why I couldn't get any grip.

No one ever told me that the drummond suspension I have needs the brushes/bearing re-geased every 2nd event or so. I had never re-geased in the 2.5 years of owning them. I must sound like a dumb arse by now. Anyway. I did a re-gease and its like a new car, amazing!!!! I did an event last weekend and got 2nd overall, 1 second off 1st place, betting a bunch of EVO's that would normally bet me by a big margin. Car felt safe and speed came without trying.

Finally got some traction and speed back!!!! Yay

I love betting EVO's!!!!! I'm the only Subaru left in the club now. So nice to put in a good show and get 2nd overall. Tho it was an EVo first.

I have some major engine problems as well. Blowing about 1.5 litres of oil out oil breathers for 10kms of racing. But still good enough for 2nd. Next year I'll have a fully rebuilt and forged engine and a LINK G4 storm professionally tuned. Hopefully a first overall win is on the way.

Thanks for everyones help.