i know some of you have deleted the PSD and converted the diff to a manual ajustment to fix the rate of locking, i am doing this as well on my orange project car (see related thread if curious). i wonder if anyone has advice on two aspects:

firstly the bolt mechanism itself. ive posted a pic of a blanking plate with a locking nut going through it, is this what others have used? im concerned that it dosent have the lip on the inside which might(??) be holding the rubber seal in place in the diff housing - is this a concern? also, i notice that the original has some sideways movement in the arm, presumably to compensate the arc of movement of the arm its pushing against, do i need a more complex arrangement to accomodate this?

second point, how do you determine the correct amount of locking??

thanks in advance

 

bump!

 

Can't help Nick but where did you get that plate and bolt assembly I will need one for my car.

Cheers Greg

 

Why do you want to delete the PSD?

 

I looks like he took a piece of plate and welded a nut into it, correct? People like to delete it that are going to run it hard as it tends to unsettle the car in a racing environmnet.

Good luck.

 

thats exactly correct, the plate is just shaped steel with a nut welded on to it which a friend of mine made up. the reason for 'deleting' the PSD is because its not there to begin with. we are retrofitting this 5spd transmission into my 86 auto which does not have the PSD as stock. i dont think there is that much to gain from the PSD system as opposed to a conventional fixed LSD. i really like the fixed LSD which i have had in both of my cars including the auto.

any advice on the blanking plate/bolt assembly?

 

PSD actuating fork has round dimble at upper end, there is rubber grommet mounted to gearbox casing which has small metal piece in it's center that is between fork and piston. Small metals other end is flat IIRR. Forks movement is so small that it should not matter that bolt is static. It will press flat metal into fork anyway.

Minimum tightening you need to set is that excess play is removed from the fork. Normally this is set up by adjustment bolt at other end of fork. To set up amount of lock you can possibly use same method as is used to set basic locking torque. See WSM 39-212q. How to count what Nm corresponds to what % of lock is other matter.

 

erkka, do you thinkthe rubber grommet instaled in the side of the case will fall outwards without the lip that you can see on the original slave cylinder pictured??

 

i had seen the pages in the WSM that deternine basic locking tourque, may nedd to study them more closely...

 

Probably not. Mine is stuck so hard it didn't fall of even when I had gearbox case washed in machine shop parts washing machine. If you want to make sure it doesn't maybe you can put suitable sized washers between grommet and blanking plate. I think there is ledge in case which will prevent them falling inside.

You'd need to find how tight WSM measuring method is at 100% lock. Maybe it's 100Nm as WSM 30-212r mentions to tighten that far and then back up to 20Nm, which can be 0%. I think this measurement can be done while gearbox is in the car as long as pinion turns freely. Also if you can find movement range of the piston you should be able to calculate Nm's based on bolt protrusion. That is if Nm figure change linearly related to piston movement.

 

cheers mate, thats good info. ajusting the bolt should be possible on the car as long as it dosent require much tourque itself, you can get a hand up to it ok. i will see about adding some washers too, just in case.

 

Hi Nick,

Jumping a little late here, but looks like you got exactly what you need. That is almost exact set up is what was used on the '91 auto I have. It was in place for over two years of track events and performed perfectly. No issue with the "boot" inside. Amount of lock was SWAG'ed by adjustment and feel on the track. I think we started by turning the bolt until it reached the full extent of the plunger travel then backed off three rotations....Seat of the pants from there. It would be interesting hear if you can create a chart showing % lock by turns/torque/etc.

Good Luck!

 

cheers scott, nice confirmation there... so i wont worry about washers at all! what percentage lock do you guess you have on the LSD?

 

nick,
that '91 trans was in my previous track car. used a setup much like yours and basically locked the differential. it performed very well on the track but did squeal a bit under tight turns in the paddock.
mark anderson has also used a similar setup.

 

Nick,
Did you ever get the PSD delete working or did you abandon this?

How many turns out from full gets you to 40%, same as the LSD? Correct me if I am wrong, but by using the bolt method, both tires are engaged at all times, unlike the LSD, but what happens when you go around turns? Is this going to wear out things at an accelerated rate, or does the PSD unit release one wheel or something? If it does not release, then isn't this thing going to spin out all the time when under power going around turns?