My new to me LSD - is there something missing?

[Kroggers]

I purchased a used LSD to put in my 915 transmission when it is rebuilt to go with the 3.6 transplant, and having had a closer look at it and the parts i got with it i am wondering if there is anything missing - or if this is all I need to be able to install it

[TechnoViking]

Well, you'll need the carrier bearings off of your old differential. And the Pinion shaft that matches that ring gear

[Kroggers]

Thank you, but sorry for the next stupid question - is the pinion shaft already in my transmission, or do I need to purchase that part? I will let an expert do the work, but i want to know what to get for the job before I drop it all off...

[john walker's workshop]

you need to mount your ring gear on the posi unit. new bolts and lock tabs. then your original bearings and shims are installed on the same side of the diff that they came off of. then assemble it with some white grease and check the contact pattern. ZF posi units tend to be a bolt in, because their dimensions are pretty much the same as the non-posi diff. i'm sure there will be some discussion about that, but that's my experience. the one in my car has been quiet for 5 years using that procedure. and you can do the job with the trans in the car too.

[jpnovak]

The pinion shaft and ring gear (crown wheel) are matched. You must remove your current ring gear from your open differential and replace the ring gear on your new LSD. Make sure to use new bolts to fix in place.

Since the pinion gear is fixed to the case you should not need to set the pinion depth. You will need to shim the new LSD side to side to make sure the backlash (pinion mesh) is set correctly. This is usually verified with a micrometer and also a grease smear pattern test. You can search for "set pinion depth" or "swap Ring and pinion" for more information.

Yes, the differential carrier bearings must be moved between the two differentials. I would personally start with the same shim stack on the bearings for the first measurment. If made well you may not have to do many changes.

[Kroggers]

Thank you all for the feedback, but the 915 is a black hole to me. I will not do the work, I will drop it in to a specialist to do, but to save time and money, I can get the required parts first (long story and not relevant now).

What I am trying to find out is if I need to order any additional parts to enable him to install this LSD into my 915 or if all other required parts are already inside my box.

I know, I am an idiot with no idea how this thing works - at least I am letting a professional do the installation, it is just I can get the parts cheaper than him and faster

[Matt Monson]

Originally Posted by john walker's workshop

ZF posi units tend to be a bolt in, because their dimensions are pretty much the same as the non-posi diff.

That LSD doesn't look like the 915/930 ZF units I am used to seeing through my place...

[Kroggers]

Originally Posted by Matt Monson

That LSD doesn't look like the 915/930 ZF units I am used to seeing through my place...

That is interesting, as it was sold to me as a ZF unit for the 915 transmission in my 1978 911SC - you saying I have been sold something that will not fit

[Matt Monson]

I'm saying I don't recognize that LSD.

[TechnoViking]

Here is a nice article about aligning the ring and pinon without the factory special tools. It is not a Porsche, but all the fundamentals are the same (IMHO). You can buy yellow or blue gear matching compound at Napa and try that differential to see how well it's going to fit....

http://www.pirate4x4.com/articles/tech/billavista/Gear_Setup

[Kroggers]

That is cool info TechnoViking, but as I am having a proper specialist install the LSD it is at this point not relevant to me - but good for those that might follow after us and want to do the job DIY style. What I am trying to find out is if I need to order any additional parts to enable a successful installation of this LSD into my 915 transmission when I hand it all over to the expert.

[john walker's workshop]

Originally Posted by Matt Monson

That LSD doesn't look like the 915/930 ZF units I am used to seeing through my place...

i missed seeing the cuyouts on the end. if i view my screen too low, it doesn't show detail as well. yeah, looks a bit different than the normal ZF.

[Kroggers]

Originally Posted by john walker's workshop

i missed seeing the cuyouts on the end. if i view my screen too low, it doesn't show detail as well. yeah, looks a bit different than the normal ZF.

As one of the experts, I appreciate your input John... If this is not a normal ZF, what is it then - it was sold to me as a ZF that would fit my 915
Will this fit, or have I been coned

[TechnoViking]

It certainly looks like *some* LSD, as it is definitely not an open differential. Are there any numbers or markings on it?

[Bill Verburg]

Originally Posted by Matt Monson

I'm saying I don't recognize that LSD.

It sort of looks like mine, this is a late ZF, this one has the extra gear for the internal pump for the cooler

[Kroggers]

Yes, it does look a lot like the one that Bill has posted pictures from. The only markings on it that I can find is this - 4061006312 33564 S40

Bill, did your one come from a 915? Will my LSD fit my 1978 911sc 915 transmission do you know?

[Bill Verburg]

Originally Posted by Kroggers

Yes, it does look a lot like the one that Bill has posted pictures from. The only markings on it that I can find is this - 4061006312 33564 S40

Bill, did your one come from a 915? Will my LSD fit my 1978 911sc 915 transmission do you know?

Yes, mine is from an '84 RoW 915

[Matt Monson]

Bill,
Thanks for clearing that up. It's been a long time since I've seen a late 3.2 Carrera LSD. It looks a lot like the last of the ZF diffs that they used in 5spd G50. I see those from to time, but it's been a few years since I've seen that version of a 915/930 LSD.

[Kroggers]

Great, so we have managed to decide that I have a late ZF that will fit my 1978 915 transmission. Then I can stop panicking

Would someone now help me with the original question - is there any additional parts that I need to purchase to facilitate the installation of this LSD into my transmission, or is all other required parts already in my 915?

[Matt Monson]

You will want to get new bearings and new lock tabs for the back on the bolts. As John Walker mentioned, it may be a straight swap but it's possible different shims will be required. If you are working with a shop that does a lot of gearbox work they should have an assortment in various thicknesses on hand.