How to verify that there is/is not a LSD

scca_ita · 01-06-2004, 07:55 AM

in a trans that is not installed? (73 915 Trans)

The numbers are 7321142 if that matters or is there a factory indicator somewhere on the case?

Thanks

targa911man · targa911man's Garage

Turn one of the cv's. If the other one turns in the same direction it's lsd. (I assume your acronym is for limited slip differential.)

targa911man · targa911man's Garage

I should clarify that I meant if the other one turns in the same direction while you're turning the first one.

scca_ita · 01-06-2004, 10:28 AM

Well mine turns the opposite direction so I guess there is no LSD......

speeder · speeder's Garage

It must be in neutral, verify that the shifter rod is in the middle position, fore/aft.

jpachard · 01-06-2004, 10:51 AM

Lick it..

James

Grady Clay · 01-06-2004, 10:53 AM

Not necessairly so.

The LSD in a 915 is just that - limited. When there is sufficient torque applied theough the diffrerntial then the two side gears are forced together and the clutches tend to engage. If the clutches are set "soft" or have many street miles at all then the "turn the axle-flange" test won't work. It acts just like a regular differential.

Take the far side axle-flange off, undo the side plate and look. A LSD has a machined and welded cylinderical housing. A regular differential has a semi-spherical cast housing. Obvious difference.

When I use a LSD, I set it up so it takes a large wrench to get the two axle-flanges to turn in different directions. The car is much more stable in transition from trailing throttle oversteer to power oversteer and back to neutral handling by apex and out of a corner.

If this is for a race car, have a welding pro weld a stock differential solid. This should be done with the axle-flanges torqued in place and by someone who knows how to weld alloy steel to cast steel. The ring gear and bearings should be reboved and the entire assembly heated appororiately.

304065 · 01-06-2004, 11:25 AM

Quote:

Lick it..

I tried that. Nothing happened.

I think I have gotten "burned!" And the trans is out of a '68!

Grady Clay · 01-06-2004, 11:55 AM

John,
If it is a ’68 then it has an aluminum case and is a 901 trans. The magnesium case 911 trans came out in mid ’69 but if you ordered a LSD you got the alu case. The LSD for ’70-’71 911 trans is the same as 915 I think. Of course 915s came out with the ’72 model year. You will find different P/Ns depending on the LSD clutch set-up.

In addition to a serial number, most transmissions have a type number also. If it is a early trans it will have a 901/?? type number. If a 915 it will say 915/??

Don’t despair, the 901 trans will find a nice home in someone (else) early 911.

When you buy transmissions that are out of the car, it is easy to partially dissemble and inspect, no special tools needed. If you know what to look for, most problems are obvious.