Brass Shift Fork Pads - A568 - Prototype Review Discussion

[BadAssPerformance]

I know I have mentioned these parts before in the Z's Update thread, however, after discussing these with Tommy, Jackson, etc. and since I just got some updated info and pictures today, I thought I'd just put it all in one thread.

This thread is about Prototype Brass Shift Fork Pads for the A568.

Why brass? The original thought was that they would provide a more positive shift feel and they would be stronger and more durable than the stock plastic pads. Only concern is the frictional properties of brass vs. plastic in regards to the pads' secondary function of slowing the geartrain down between gears.

Brass pads CNC machined out of regular brass bar stock - specific grade unknown.

The test trans is a '91 A568 put together in 2008 with Brass pads on both the 1-2 and 3-4 shift forks leaving stock plastic ones on 5th.

The test vehicle is my '87 Shelby Z 2.4L ~500FWHP

Test prototypes have been subject to approx 200 miles including over 100 trips down the 1/4 mile, typically shifting at 7k RPM. Maybe a dozen of those runs included WOT shifting into 3 and 4.

I have not measured the wear but it is what I would call significant for the amoutn of use. I am contemplating if new plastic ones would have lasted as long or longer?

Pictures below show the stock and brass pads for comparison and current condition including wear.

Discuss.

[Juggy]

i think you would be better off designing these in a metal type such as ampco or even one of the biiitchiest metals to machine, mold max!

they have much better wear characteristics

[BadAssPerformance]

Good suggestions, keep them coming. I was thinking harder brass or bronze or something?

I used brass mainly as I needed them made quickly (to get the car togetehr fro SDAC-18) and had material available, and have heard of others using it.

[Juggy]

well the 2 i suggested are copper related. they are much better for heat/wear

berllium (however its spelt) can be found in the mold max, as well as some ampco this is what adds even more strength to the copper

question is, how hard do we need these things??? can it be over done and end up creating more wear elsewhere internally like syncros or what not?

[supercrackerbox]

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[Pat]

In the pictures, it doesn't look like they are wearing evenly, which can be part of the reason why you've experienced the shifting problems you've had.

[BadAssPerformance]

Are you looking at the 1-2 pad? yes those are uneven but I can usually hit 2nd... whats uneven about the 3-4 pads? 3rd has been the issue.

ETA: BTW... it had 3rd gear issues when the pads were brand new and had gotten better until recently

[BadAssPerformance]

well the 2 i suggested are copper related. they are much better for heat/wear

berllium (however its spelt) can be found in the mold max, as well as some ampco this is what adds even more strength to the copper

question is, how hard do we need these things??? can it be over done and end up creating more wear elsewhere internally like syncros or what not?

Yeah Berillium is ex$pen$ive but good stuff. Not sure if it wants to be too hard.... Guess I need to look up material yeild strengths

[Directconnection]

Yeah Berillium is ex$pen$ive but good stuff. Not sure if it wants to be too hard.... Guess I need to look up material yeild strengths

I look into lubricity properties 1st. Probably why they used "plastic" Is that nylon or a delrin? I'd look into a graphite composite possibly w/teflon?

Man, I think we need a resident Chrysler Engineer from the old days to shed some insight here for us on time to time (hint hint)

[Juggy]

I look into lubricity properties 1st. Probably why they used "plastic" Is that nylon or a delrin? I'd look into a graphite composite possibly w/teflon?

Man, I think we need a resident Chrysler Engineer from the old days to shed some insight here for us on time to time (hint hint)

nice thinking!!

uummmm theres another metal that would work pretty good too. but its kind of hard and sticky to machine, i cant even remember what it was called, but the stuff is perforated, its made with all kinds of tiny micron sized holes to allow air to flow through the piece of metal. altho i do not know how big of a micron it would take for oil to allow to "soak" into it, it was more or less designed to flow air.

but after writing that and noticing you mention teflon...are you saying it is best to shed the oil from the pads, rather then absorb?

[cordes]

I've got a set of 525/520/555 pads at the machine shop now. I'm waiting on a quote, but the guy is taking forever. You would think the economy is in full swing the way they are knocking out expensive looking stuff in there.

Anyway, I do think that they need to be made out of a harder material. The guy at the prototype place was recommending hardened bronze, but I don't know what he is basing that off of.

My concern with going too hard is that we will start to wear the slider that it rides in since it is only Al if I'm not mistaken.

Either way, we need to do something. All of the transmissions I'm pulling apart these days have rough looking fork pads even if the gears look good.

[Directconnection]

I've got a set of 525/520/555 pads at the machine shop now. I'm waiting on a quote, but the guy is taking forever. You would think the economy is in full swing the way they are knocking out expensive looking stuff in there.

Anyway, I do think that they need to be made out of a harder material. The guy at the prototype place was recommending hardened bronze, but I don't know what he is basing that off of.

My concern with going too hard is that we will start to wear the slider that it rides in since it is only Al if I'm not mistaken.

Either way, we need to do something. All of the transmissions I'm pulling apart these days have rough looking fork pads even if the gears look good.

They used a "plastic" from the factory for a reason.... NOT because they were being cheap arses. Let's try and find out why (too hard wearing out the synchros?)

[cordes]

They used a "plastic" from the factory for a reason.... NOT because they were being cheap arses. Let's try and find out why (too hard wearing out the synchros?)

Actually, I'm willing to bet that cost was a major contributor in the decision to go with a plastic piece. The cost of raw materials alone would make for a huge price difference, let alone the cost of casting or machining vs. molding plastic. That would make a very large difference spread out over thousands of units to a bean counter.

Are you suggesting that the plastic pads compress somehow to allow for some desired effect on the synchro ring or any of the dogs? Or are you suggesting, as I did, that the plastic is softer than the Al so it won't wear the grove it rides in like another material may?

[MiniMopar]

The pads ride in a groove in the slider. They don't touch the synchronizer (stop) rings. The slider is extremely hard material...it has to be. It is what is taking the material off the dogs of the gears! Synchronization happens due to the friction between the stop ring (which is always engaged with the slider) and the cone on the gear. Push a stop ring against gear in your hand once and try to spin it. It makes an impressive amount of friction for something dripping with oil. The friction between the pads and the slider pales in comparison and since the slider is always fully-engaged to the mainshaft (the wheels), it plays no part in synchronization of the gears anyway.

As for cost not being the issue...I'd have to disagree with that one. Once setup with the molds and process, you can pop out thousands of pads for what it costs to machine one of them out of brass or any metal. There may be some wear advantages to plastic but it comes at a big cost: durability.

[BadAssPerformance]

Are you suggesting that the plastic pads compress somehow to allow for some desired effect on the synchro ring or any of the dogs?

I thought about this the first time I missed 3rd with this trans. I think the softness of the plastic allows them to possibly grip the sliders' side walls to help slow the geartrain during shifts maybe?

Or are you suggesting, as I did, that the plastic is softer than the Al so it won't wear the grove it rides in like another material may?

Hmmm... I'll look for wear in the sliders.


BTW everyone, generic "brass" is soft. I wish I knew what grade I was using (it was an unlabeled chunk on the shelf inthe shop) , however most common grades are VERY similar to the hardness of typical engineered thermoplastics like Acetal (Delrin) and PA66 (Nylon) ... I'm thinking about making some out of harder brass now? hmmm...

[MiniMopar]

I thought about this the first time I missed 3rd with this trans. I think the softness of the plastic allows them to possibly grip the sliders' side walls to help slow the geartrain during shifts maybe?

The sliders are always engaged to the main shaft. The main shaft is always engaged to the diff and therefore the wheels. The input shaft is what is being synchronized to the main shaft, so the friction between the pads and the slider has no effect on shifting other than to slow your car down a very tiny amount (plastic brake pads).

BTW everyone, generic "brass" is soft. I wish I knew what grade I was using (it was an unlabeled chunk on the shelf inthe shop) , however most common grades are VERY similar to the hardness of typical engineered thermoplastics like Acetal (Delrin) and PA66 (Nylon) ... I'm thinking about making some out of harder brass now? hmmm...

I think bronze might be ideal, but I don't know how that is to machine or how brittle it can be?

[Directconnection]

Oilite (sp?) is a bronze used for making bushings. They have an oil impregnated into it. Kinda funny when you machine them, as they start smoking like you are using cutting oil. You can see the oil weep out when it gets hot.

[Juggy]

The sliders are always engaged to the main shaft. The main shaft is always engaged to the diff and therefore the wheels. The input shaft is what is being synchronized to the main shaft, so the friction between the pads and the slider has no effect on shifting other than to slow your car down a very tiny amount (plastic brake pads).



I think bronze might be ideal, but I don't know how that is to machine or how brittle it can be?

does not sound like a very good cost effective alternative, it is also more prone to corrosion and i cant see it having very good thermal properties considering it will heat up and cool down with the trans

[black86glhs]

Ballistics nylon? Would that make the trans.......wait for it...........bullit proof???!!!

[Reeves]

I look into lubricity properties 1st. Probably why they used "plastic" Is that nylon or a delrin? I'd look into a graphite composite possibly w/teflon?

Man, I think we need a resident Chrysler Engineer from the old days to shed some insight here for us on time to time (hint hint)

The '2.2 Complete Review' book (1983 or 1984) says they ditched the stock pads for racing, and built the fork up with weld and then machined to fit in the slider.

I've got a set of 525/520/555 pads at the machine shop now. I'm waiting on a quote, but the guy is taking forever. You would think the economy is in full swing the way they are knocking out expensive looking stuff in there.

Anyway, I do think that they need to be made out of a harder material. The guy at the prototype place was recommending hardened bronze, but I don't know what he is basing that off of.

My concern with going too hard is that we will start to wear the slider that it rides in since it is only Al if I'm not mistaken.

Either way, we need to do something. All of the transmissions I'm pulling apart these days have rough looking fork pads even if the gears look good.

My vote is for the bronze.

Slider is not aluminum. It is cast steel or iron iirc.

Oilite (sp?) is a bronze used for making bushings. They have an oil impregnated into it. Kinda funny when you machine them, as they start smoking like you are using cutting oil. You can see the oil weep out when it gets hot.

And, generally speaking, when you see that oil coming out when it's hot, it's about empty.