Millermatic

I've searched videos and forums... and have found conflicting information.

I'm taking the clutch bell housing off my '86 Turbo to check the clutch and flywheel. Can I just remove the speed and reference sensor or do I have to remove the mounting bracket they are on as well?

The factory manual wasn't particularly helpful. Nor was the otherwise great tutorial from that site that I've spent tons of money at over the last two years. There's a comment on the bottom from a user mentioning the article needs to be changed to indicate removing the bracket.

I'm hoping I can leave the bracket on. While I'm pretty sure I can get it off without (too) much trouble... I'd have to adjust the sensor spacing if I did that... and I can't see how I could do that without taking half of the top of the engine apart. Or shrinking my arms and adding a few extra joints. The engine is just recently all back together and tearing it back apart would be a bit of a bummer.

For those that might have caught my post on my Pinion/TT/CV question... this is related. I'm having Black Sea R&D rebuild my TT... which had some strange damage on the splines and some rubbing damage on the shaft in an area that is inside the housing. Since I'm 90% there... I'm going to check to see if I can find what caused the damage.

931guru

1) Remove the bracket, makes it much easier to remove the bell housing.

2) Adjusting the bracket is simple... Find a piece of cardboard .8 mm thick, cut out a disk the size of the end of the sensor, and glue it on (the one that looks at the starter ring gear.) When adjusting the bracket, move it towards the flywheel until it can go no further. Tighten the bracket and you are done. The cardboard shim will abrade and disintegrate and the sensor will be at the correct distance.

Droops83

I have always had success by only removing the sensors (Southern CA climate) from many customer cars (bellhousing is still easily removed) , but finally had an '89 951 last month with the original (!) speed/ref sensors that simply would not come out because they were corroded in place. I had to physically break the aluminum bracket with a pry bar to remove the sensors! Luckily the updated sensor bracket and shielding sleeve are still readily available from Porsche and this one is happily running.

But, good tip with the cardboard, that is a much better idea than a metal washer!

Millermatic

Appreciate the replies. The sensors are new and will come out fine. My understanding is that later turbos have a sleeve on the bracket that goes into the bell housing making removal w/o taking off the bracket impossible?

My concern is that I can use an extension and a wobble to get the parts off... but I was assuming I would have to be able to reach the bracket with my hand to adjust it on reinstallation. Which would require taking more stuff apart than I would prefer.

Droops83

You are correct, later brackets with sleeve (which was added by Porsche to counter EMI from the late-type smaller, permanent magnet starters) could have the sleeve seized in the bracket, but that would not prevent bellhousing removal, because the reference mark sensor/sleeve (closer to engine) opening in the bellhousing is slotted, as shown in the photo of a horribly crusty spare bellhousing that lives in my garage. Living near the ocean is great, but this is what salt air does to aluminum!

Dan Martinic

Chris the slotted bellhousing did not last for long: Porsche went back to "fully enclosed" shortly after (there's a TSB on this). My original '88 951 has the sleeve but no slotted bellhousing

Millermatic

I got it off without removing the sensor bracket. Mine did not have the slot. (‘86)

What a complete PITA. The top bolt on the bell housing had threadlock on it... and was nearly impossible to reach. And I’m still not sure what the housing got stuck on when I was trying to get it out.

I think I’m going to remove some of the vacuum lines and drain the coolant so I can take off the heater control valve and associate hoses when I put it back together to give me a little more room to maneuver.

Clutch looks fine (previous owner said he replaced it... but my level of trust is fairly low since discovering the trashed ring and pinion). I’m a little concerned about the teeth that engage the drive shaft. There was a fair amount of damage to the splines... and I’m wondering if this didn’t chew up the... whatever the part on the clutch that engages them is called. I’m going to at minimum pull it to change the pilot bearing and check out the flywheel. I’ll check out the teeth then.

I’m wondering if I should just replace it all for peace of mind. At this point I’ve literally rebuilt just about everything else on the car. After the transaxle rebuild including a new ring and pinion and a TT rebuild at Black Sea R&D... what’s another $1000 in parts? (Ouch)

I’m going to go have a beer now...

Droops83

You are correct, sir! I just looked at the photos from both of the customer '89 951s that I have in the shop now (one of which is mentioned above, had to break the bracket to get the sensors out!)

The OP has an '86, so he might have an easier time with this!

Dan Martinic

I bet it was getting hung up on the little "pins" that are used to hold the heat shield. There are a few of these. I cut mine down (kinda snipped them with heavy-duty wire pliers) and the bellhousing went back in FAR easier...





It's a tough job for sure. I got to the top bolt from the engine side. If I recall correctly, I started the top bolt from underneath... but finished it from the top with a backwards-angled long-handle and short socket arrangement--kinda jamming it between the cables. Brutal! And what about that bolt at nine o'clock with that heat shielding in the way? Talk about interesting.

I'm not sure what "teeth that engage the driveshaft" refers to. If you're talking about the splines, then I would imagine the clutch disc is also ruined, no? Sounds like there's an alignment issue. Is the guide tube worn on one side? The guide tube is the part still attached inside the bellhousing

Millermatic

Yeah... I noticed the pins. I couldn’t see them when the housing was jamming... but they are a top suspect. I think I’ll shorten them.

The center of the clutch disc, yes. Guide tube looks fine. The teeth on the clutch disc have a fair amount of corrosion... which seems... bad.

Millermatic

My shaft is the one on the left. The one on the right was the one that Constantine at Black Sea used to show me how screwed up mine was. As a result... it's now mine, too...

Constantine

I'll jump in for some more context.

The original drive shaft has damage below where the clutch disc splines engage the drive shaft splines. If one looks closely, the splines below the ghost marked area from where the clutch disc engages the splines seem to have been worn by something rubbing on them. This contact flattened the splines enough so a clutch disc cannot be pushed down the entire length of the drive shaft splines as can normally be done.

The drive shaft itself below the splined portion has also been worn down by contact with something in the front bell housing as can be seen by the shiny marks around its circumference.

The drive shaft end nub is very worn too. The drive shaft on the right has been refurbished and shows our correction for a worn end nub.

By the way, that Sachs disc is pretty rusty so it might be a good time to replace it as well and maybe even resurface the clutch WYIT.

HTH.

Millermatic

Thanks Constantine! As you’ve noticed... I took your advice and pulled the clutch.

Northern_aqs

While you’re in there resurfacing the flywheel, I would change the rear main seal. It’ll be the cheapest part of the whole project.

Tom M'Guinn

Guide tube broke free maybe?