Synchro brake bands, Do these wear out? Options

[bobhasissues]

I refreshed my transaxle two years ago and after a few thousand miles decided to return the car to the jackstands for other restoration projects. I'm closing in on getting the car back on the road, but would like to resolve the trans issue before I put it back into the car. After changing the dog teeth. slider and synchro on my second gear, I was still experiencing an occasional click/grind when shifting from 1st to 2nd. I tried two different brands of synchros with the same results. Needle bearings on all gears were in great shape. Clutch and shift rods are properly adjusted. I have never heard any mention of this, but was wondering if the brake bands or anchor block ever wear out and need to be replaced.

[brant]

bands wear out
they should be rough and dark colored
once they are shiny or smooth, they are shot

I've heard of people flipping them 180 degree's to use the other side
the builder I worked with won't do it. Replacement only. but I can see how cutting corners isn't wise when your in the business.

brant

[pcar916]

I don't think he's talking about synchro bands but the brake-blocks underneath them.

I've replaced broken ones before but those parts have "long legs" and I haven't seen too many worn out ones. There is an early style that should be replaced with later ones if you find them. Someone else might remember what year they switched over. There are a few things to remember even with new parts in a transaxle with servo-type synchros like Porsche used until they came out with the G-50 series trans that use the Borg Warner style synchros.

1: Always make sure your clutch is properly adjusted
2: Push the clutch pedal all the way to the floor BEFORE you shift up or down.
3: Shift slowly... no speed-shifting
4: Match engine and trans speeds whenever possible rather than, for instance, let the engine spin down between up-shifts. Do the same when downshifting.
5: Make sure that you use good lube and that the fluid level is where it's supposed to be.
6: If you have to go in there again when all external things have been eliminated, Make certain that the slider is absolutely centered on the spider between 2nd and 3rd, and that the fork isn't binding it one way or another. In fact, there is another thing you can do too.

If you are in there anyway and have an extra set of blocks, put them in your 1st gear and synchronize the downshift from second. Why? Because you can.

Good luck!

[Cap'n Krusty]

They wear out. Worldpac carries them, indicating a demand.

The Cap'n

[r_towle]

What type of gear oil have you been using?

Rich

[bobhasissues]

What type of gear oil have you been using?

Rich

Swepco 201

[ME733]

......All good advise in every post...just a comment,..."Brake Bands "can be flipped over and reused., BUT, they cannot be "Shiney" to the point they are totally worn out to death., Their O.D. which will be on the Inside after flipping must be close to O.E.M. size., generally when the brake bands are "shiney"and worn out to death, the "DOG" teeth will also be dead. necessitating replacement with new or from another gear, (such as 4th, or 5th.)....all this is a "down and dirty" economy rebuild state of affairs,as you have Bills to pay and a family to feed. It does work...nothing beats new parts...Transmission Oil...the trick stuff, with mos, or synthetic, will CAUSE shifting problems, as the brake bands are too slick to slow down properly for engagement.(synthitic can also cause rusting of internal parts)., good old 80/w/90 gear oil will work out fine.Just like the factory recommends.

[r_towle]

What type of gear oil have you been using?

Rich

Swepco 201

I personally stay away from any synthetic gear oil because the brake bands were not designed for it, and I have been told that it can actually wear them out faster.

Swepco (not sure if its synthetic or not) may be fine, but its just a word of caution.
It is specififed for the later transmissions, but we are not using those transmissions...so not everything that works for the 911 is right for our cars.

One thing that may be your issue, aside from the brake bands wearing, it the bearings at the intermediate plate move, and the case bore for the bearing do get ovaled out over time.

In several of the cases I have , the inner bearing seat is to far out of spec to re-use the case. It may be rare to have this happen, but I have two...so its not super rare.
Hard to feel, easy to measure.
These were on race trannies so they have experienced a tough life...

I also found that the position of the shift fork makes the number 2 gear either work perfectly...or work as you you are experiencing.
I have an old case that I use with a large cutout to mount the gear stack so I can position the forks correctly.
Even with all the specs, I have had to fiddle with that number 2 fork to get it to shift fast and easy into the number 2 slot.
Its just a hair in either direction...
Shoot for a neutral position and I even favor the number 2 side to ensure that the number 2 gear is up to speed.
If you somehow adjusted the shift fork so the brake band is always rubbing (BTDT) then it will wear out pretty fast...and that may be your issue.

If it was me, I would pull the gear stack again...take a magnifying glass and look at the brake band all the way around...look for a wear pattern.
Feel it on the number 2 side of the band (it has a crown..each side serves one gear)
Inspect the current position of the brake band while the tranny is in neutral and spin both gears on either side by hand...
This will let you FEEL the resistance ...
If its rubbing (I am talking about 1/32 of an inch here) you need to move it.
Your total adjustment is about 1/4 of an inch front to back...so its not to much.

It may have just been aligned incorrectly and needs to be replaced and adjusted again...it happens.

Oh, inspect the magnetic drain plug....
If on a recently rebuilt tranny you find a build up of metal on that plug....look more closely at the gear stack and find out why.

I also stick with simple 70/90 weight DINO gear oil.

Rich

[Richard Casto]

I am not sure everyone is on the same page with respect to terminology/names. Specifically I think people are saying "brake band" when they probably mean "synchro ring". So that is confusing things IMHO. (IMG:style_emoticons/default/headbang.gif)



So this is a photo of the various parts that make up the Porsche Synchromesh (I left out the large clip that holds it all together). Specifically these are what you would find in 2nd through 5th gear. 1st is very similar.

Everything wears. Everything can break. But in general the wear items are Synchro Rings, Synchro Hubs and Sliders.

To the original posters question...

I don't consider brake bands, thrust blocks and anchor blocks to be wear items. Brake bands can break and that will cause problems.

Others have given good info regarding what might be causing your shift problem.

Richard

[bobhasissues]

I am not sure everyone is on the same page with respect to terminology/names. Specifically I think people are saying "brake band" when they probably mean "synchro ring". So that is confusing things IMHO. (IMG:style_emoticons/default/headbang.gif)

Richard

Thanks Richard for the clarification, the question was specifically about brake bands and anchor/stop blocks, not the synchro itself. I was ignoring those who suggested flipping the brake band since I'm assuming they meant the synchro and not the brake band.

[Dr Evil]

The bands can bend over time and the blocks can fail and break. Used ones are fine, new ones are like $15+ ea and that is not necessary. If you need some, I may have them. There are two sizes depending on your year of guts. Let me know and you can have some for free.