Goughary

There are a bunch of diff lock threads...so here's another!

Interestingly enough, our diff lock was also used for the 928 S4...we just happen to have 2 of them and the 928 had only one for the limited slip across the rear wheels.

I was doing a full fluid flush/bleed on the world's most perfect C4 today. 22k Miles on this car. And it's insane- like it rolled out of the showroom yesterday...i swear this was likely kept in a climate controlled room for 30 years...



And what's funny about perfect cars...or rather perfect 964s...is that they can't be. Cuz honestly, they weren't perfect when they were new...they all need sorting.

This one, seems to have sit for a bit. So few miles. And one of the lovely things that happens when a car sit's, is crystallized brake fluid. Which wasn't apparent until i got to the last part of the bleed, the longitudinal diff lock...and i noticed it was pouring fluid on the floor. When things don't get used...ugh...

Soooooo, it just happens, aside from having enough parts in my attic at this point to build a brand new 964...





I made a bunch of diff lock seal sets. And happen to have them around. So thank god we did this at my house.

I have more sets, so PM me if you haven't rebuilt your diff locks yet. And when i run out, i can have more made....cuz we all need them.

Anyway...out the little bugger came...

There is a spring clip, you take that out, and it just comes apart. A little compresssed air through the brake hose opening - just a little, don't Shoot the piston across the room please...and it's apart



Then take the old seals out. Make careful note of the orientation of the center seal





Then if yours is gunky- clean it carefully - don't scratch the channels..



Then reinsert the seals. The outers are just guides. They are split, so you just wrap them around. The center is a black oring and then you put the blue seal over that in the same channel. You put some tape over the outer channel to slip the center one on first. It'll make sense when you do it. It's ok to stretch the seals a little, as they will compress back into shape after...







And that's it. Easy enough. Diff locks are close to 1 thousand dollars from Porsche, so sealing them is the way to go. Seals are not cheap, but it's just a better alternative than replacing the lock.

I'm thinking about making up clutch slave seals as well, cuz I'm also sick of replacing slaves, when it's just a seal that goes. If i could find the clutch slave boots, I'd make the seals tomorrow.

Anyway, if you have leaking diff locks, PM me and i can send a set of seals. I have a few left, and will make more as needed.

gregmitch

I couldn't get over how perfect that car is when I saw it. I'd be afraid to work on it lol.
Can't wait to see my car on stands in that garage soon.

LM964

This is the C4 diff lock for the front, yes? - the slave cylinder mounted atop the front of the gearbox/transmission casing? Did you 'make' the seals or have loads of (correct type) mixed seals that you bagged up in to cylinder sets? Interested.

LM964

Ah yes, I can see it it the front transaxle lock now - part # 964 301 051 01. PM sent.

Goughary

This one is the front diff lock yes. There is the one on the side of the trans behind the right rear wheel as well. They both use the same seals.

I made a bunch of sets of seals. If you are in Europe, ninemeister may still have or sell them as well. I found a contact in the states for a seal manufacturer and worked with them to produce seals. So now i have them for my guys and for the moment, some extras if anyone wants to buy some for themselves. And when i run out, I'll make more.

This is the kind of thing from Porsche that kills me. It's a wear part. And it's important. And every C4 I've ever worked on needs them. So since Porsche won't provide them, i have to jump in and geterdunnnn...

Goughary

I don't see the PM...did you send a pm or friend msg. I only see pm on my phone in the app...

LM964

You should have a PM now - one sent a few minutes ago.

Goughary

Got it, ty

GTgears

Goughary

Honestly- i make a huge effort w all the guys out here to make owning these cars very inexpensive...i do work for them if they like, i do it with them, i teach them, etc...and if i need to make parts or do sourcing for ways to get things done less expensively, i do it. My wife wants to kill me half the time because when work ends, i an all night Porsche's...

None of that to blow my own horn...but we got into the drive break fix drive thing to put the fun back where it should be. When you are fully able, and all of us are, to do the basics, and dig into these things, ownership is way less expensive, and it's way more gratifying....

Anyway, to all of you that keep me on my toes...thanks!

renn-boxer

Great description, Pm sent for a set for my 91C4. Thanks for your efforts and information.

Goughary

For all you guys that hit me up for seals- in my very informal way- they will show up in an envelope or package alone with no explanation ...i figure if some little blue dodads show up, you'll know they are from me...and what they are for...lol

Keep in mind there are a couple of instructional threads on rennlist and then the pics i just posted here the other day. It'll be more or less self explanatory once you have the slave apart.

Just remember the oring goes in the middle, and then the one round seal goes over that. Try to not ruin those seals getting them to the middle. I tape over the first slot, and then rig up a funnel shape thing a ma jig to get the seal on and over. You'll see...

Then...that center seal is directional. There is a pic up above with the orientation. Get that right or it will leak.

Next...make sure to clean the slave and piston. Don't use anything abrasive. Alcohol works well on the old gummy crystallized brake fluid. And a plastic scraper if you need.

Next...there is a drain hole in each slave. Be sure this is clean and clear. They actually drip for a reason. So when excess fluid does seep past the seals, it drains away from the seals in the trans. This is normal function. But most of us have blocked drain holes.

I'm half way through this run of seals. If there is demand, I'll run off another set.

Regardless i need to have them in my hoard for the random need like yesterday. That was surprising - as this was for all intents and purposes "a perfect car". The rear lock didn't leak and the front lock was gushing when the system was pressurized. Thank god i had the seals.

That said, every other C4 I've had in my clutches....had leaky diff locks. So it's common.

Anyway, enjoy the fun. And again, follow the pics - and threads. And if you need to talk through it, call or text me and I'll walk you through it. And if you break the seals and blow everything, i should have more sets to start over with, lol...

klokwerk

Thanks! Got my set today.

Hopefully I will have some time soon to do another bleed of the system.
When I did it last year I had no leaks so these will be for just in case.

LM964

Rob, when slave cylinders were serviced and re-installed did you bleed via the 'hammer' or like some others do (with no hammer), activate with ignition on the diff lock switch many times? Also I'm assuming I can clamp off the fluid line nearby and not need to bleed so much(?)

Goughary

You can't clamp off a fluid line. So what you do, is, with the car off, pump the brake until the pedal goes dead hard. This removes the pressure from the system.

Then when you take the line off the slave, it will drip, but not poor out.

I use a hammer to bleed the car. But if you don't have one, buy a set of M6 size speed bleeders. Install those in place of the oem bleed nipples, and then crack one open, Jump in the car and turn the console switch on and off for a little while. That will do the trick without needing two people.