SharkSkin

Now I know you're pulling my leg -- Seattle won?

heinrich

Yeah I know

Vilhuer

Since 11 washers are missing wonder what else is wrong? I would check tensioner piston to make sure it's correct type etc. Tension arm looks to be right version.

Garth S

Your tensioner is identical to the lower one shown, from a 1980: there are 35 washers in this one, arranged in opposing groups of 5 as shown. ( the top unit is an '85, now on my '80). I've heard of the 40 washer units, and possibly they were unique to the 78-79. In any event, as long as the shaft is 'filled up' as indicated, the tensioner works.
If needed, I can take a shot of the correct roller, etc now hiding in the parts bin.
As a pivot bolt is needed, you may consider upgrading to a newer carrier arm with the larger bushings indicated in the second shot.

kary4th

Thanks for all the answers guys!

I'll pull it apart again and compare to Garth's pics to be sure it's exactly the same.

Bill, my early WSM (printed 1980) shows both 35 and 40 ring versions. From that, I was guessing that a mixture were used on the early cars. No mention of year is made, only the part number of the adjusting screw. Weird.

Now if someone could explain how Seattle won...

Bill Ball

Yeah, ignore what I wrote previously. The switchover to 7x5 washers was 1980 (as indicated in the annual service info tech book). The adjustment bolt was changed in concert with the smaller pack. Maybe Garth and you and can compare the bolts (length and center hole depth) so you can sort out which tensioner you have.

To clarify, the tensioner body is the same 78-82. In 83, the internals were changed to add a hydraulic valve and fill bleeders were added. That's the upper one in the Gath's photo. In 85 the tension monitoring was added, also in the upper unit in Garth's photo.

If yours is a 78 original tensioner, it should be 40 washers. The fact that it only has 29 washers shows it was fussed with at some point. If so, you'd think they might have switched to 35 washers and the newer bolt. I can't figure out how it got to 29 washers. The washers can fracture. Weird.

kary4th

Bill, what are you doing up? Long night or early morning?

Bill Ball

Yeah, what am I doing up? Fussing with the car, no less. Anyway, time for a few hours sleep.

WallyP

The original tech info book on the 928 (P/N 4582.21) shows the tensioner with eight groups of five bimetallic washers, and the photos appear to show a small-diameter roller on the end of the arm.

kary4th

My adjusting bolt is 65mm in total length. Garth, does that length match yours with 35 discs?

Again, thanks everyone!

Garth S

More or less - but that's not the measure that counts: note that the bolt is hollow .....
Anyway, the bolt on my old unit is 62mm measured under the head, by convention ( or 69mm if measured as your pic) .... effectively the same: the well depth in the bolt end is 44mm, which is important - and we'll get back to it in a moment.
The total length of the piston rod from across the flat of the top piston to the bottom of the rod is 96mm. From the same top flat to the bottom of the disc washer under the shim stack is 71mm ... with 35 washers correctly arranged ( and the washer stack itself is 44mm).
That leaves 25mm of exposed piston rod that enters the hollow bolt: ( we made it back to the critical part of the bolt - phew). If the well depth of the bolt is adequate to accept this 'tail' plus the 2-3mm more that is exposed when the spring washer stack is compressed, the tensioner will function correctly .... as long as there is adequate bolt length to torque down enough to set the TB tension.
Perhaps this could have been more brief, but that's how it functions. In your case, missing at least 6 washers, your tensioner will still work reasonably if it meets the above criteria re the hollow bolt.
If you cannot find more washers easily, I'd be tempted to configure them into 6 groups of four and one of five facing the top piston ... ie

.......<<<<>>>><<<<<[piston]

Try that on for size .... it may do the job.

kary4th

Thanks everyone for the assistance.

Without additional discs (at $8 each for new ones, I can wait until I find used), I decided to put everything back together as Garth suggested.

Thanks to everyone's comments, I feel OK about this now.

I just don't know what I'd do without you guys to throw questions at.

mulik51

I think what determines if you have 35 or 40 discs is the lenght of the tightening bolt. For 35 disc set up it is longer then for 40. (it shows it in the WSMs) I think the reason you have 28 discs, is PO trying to get the discs with the piston out of the tensioner housing and using something instead of the tightening bolt to push the assembly(something longer). He wound up with discs broken, and didn't want to buy a new tensioner, so he decided to let it be. I did the same mistake, but FlyingDog had couple of disc which I could use(thanks) I think I still have one or two left if you are interested.

Klim

mulik51

Oops, too late