Kevlar Lined Bands in Auto Trannies

[Glacier991]

Ok, this may be a little esoteric for a few folks, but as I am a) getting ready to move, with a nice big garage to use for doing the work and taking the pictures for some planned new threads... and; b) busy assembling parts for a 4R70W rebuild thread...

I have run across someting I am desiring input on from those with some knowledge or experience. It relates to Bands (mainly OD and intermediate) using Kevlar as a lining material. It is touted as "heavy duty" or "able to stand up to the HD kind of use etc".... yet in some circles I hear it does not "wear in" as well as the more "normal band material" and in fact is a little harder resulting in increased slippage. (true or not).

I have run into a professional trannie guy online as a result of buying some parts from him, he seems very knowledgeable and willing to share his knowledge and I asked him. He said in the 4R70W the band lining was rarely if ever a problem and when I mentioned Kevlar, he openly wondered "what next... diamond dust bands ?"

I did procure a Kevlar OD band for the 4R70W (nearly could build one with the parts I have gathered to date) but when I saw a Kevlar Reverse drm band on E-bay I said whoa... hold on here....Kevlar, reverse?

So, now the Q. What, when, where and why Kevlar? Are the benefits real, and if so under what usage? Or is it all hype? Maybe even not a good idea?

Have at it guys ! What do ya think?

 

[bates]

Maybe its like high performance brake pads, you need to keep the bands really hot all the time to get them to work well.

 

[Billy177]

I have used a kevlar clutch before, it worked pretty good in my friends gto

make sure they are real though and not some piece of crap impregnated with 10% kevlar

 

[Glacier991]

it is worthy to remember that unlike clutch or brakes, transmission clutches and bands are essentially phenolic impregnated paper that essentially carbonizes in use to become what it is... I wouldn't be surprised if the Kevlar is not actually made into the paper making up the bands...

 

[V8BoatBuilder]

Ford used/uses kevlar as a suspention bushing in the 95-97 torsion bar adjusters. Granted, the use is completely different than transmission bands, but in the t-bar adjuster application the kevlar leaves much room for improvement:

 

[CDW6212R]

In AOD's, the reverse band usually will last the lifetime of the transmission, including all rebuilds. The factory part is cast iron as I recall. A kevlar piece might gain some lifespan for the drum though. There are different pins that can be installed to tighten up the bands.

I think that the magic in building an AOD, through the 4R70W, is to get the latest model core to start with. Ford constantly improves lubrication, valve body calibrations, and the solenoids.

If you can get Kolene steels and blue frictions at a reasonable price, try them.

I don't know if there is something better, but the last I heard, the MarkVIII direct drum had the most clutches. Various companies sell thinner direct clutches.
There is debate about whether eight or nine thin clutches is actually more reliable than six or seven normal thickness clutches.

Do remember for performance use(in an AOD), to get the OD "A" servo parts from a Supercoupe.
Regards,
DonW

 

[BrooklynBay]

What is the average life of a standard band compared to the Kevlar lined band? I know that you can't generalize the life of a band, since they all vary according to their thickness, stop, and go driving, transmission pressure, etc. Glacier once said in another thread that Kevlar bands slip, and recommended their use only on higher pressure transmissions like the 4R70W. He said that it wouldn't be recommended on an A4LD, with the lower pressure. I was wondering about the A4LD with the high ratio boost valve. Those have a little more pressure compared to the low ratio boost valve. Could they be used with those without having the slippage problem? Do they also make Kevlar lined clutch pack plates?

 

[sparky2263]

They got their start because of racing applications. The marketing guys jump in and figure they can make a buck by pushing them to everybody and everything.

 

[BrooklynBay]

Somebody told me that the old transmissions had extra heavy bands, and clutches compared to the thin ones that are manufactured today. That is the reason why the old ones lasted so long. With the modern day materials, and coatings that they presently have, why can't they manufacture thin ones that last just as long? Maybe something with a ceramic coating to resist heat, have a lot of gripping power, and would also be pretty thin like the ones that are in present use.

 

[Glacier991]

In fairness the newer engines and transmissions last longer and need less maintenance than the "old days". Materials are better and engineering is too. (mostly).

The issue with thinner plates is friction when not engaged. 4 plates holds better than 3. 5 better than 4, etc. But... we introduce additional surfaces (2 per plate) that are thousandth's of an inch apart when not in use, and spinning.... that means more friction, more heat, more resistance to movement. It is all a tradeoff.

My new A4LD rebuilds go to more plates in the direct clutch and also kolene steels. It is a place I believe in the tradeoff. I am also going to stronger application of the intermediate and OD clutch bands.... and am looking into better welds on the bands themselves. Kevlar I am still debating.... for the OD. I just wish more real data was available and less hype. I once found a website that discussed them in real world engineering terms but have been unable to relocate it.

 

[BrooklynBay]

One thing that I've been wondering about is if you use thinner clutch plates, wouldn't they be weaker, and warp easier? I know that the thinner something is, the faster it will heat up. This is the idea on baseboard heaters that are copper, and aluminum. The heavier iron radiators take longer to get hot, and retain their heat longer. Not to get off of the topic. I just used this as a comparison for the type of material being used on heating systems, and the steel material on those clutch plates.

 

[Glacier991]

They are applied as a unit.... when "squashed" .... so more plates mean more "teeth" to handle the load. There would be a point where they might be weaker, but as a rule you can asume the engineers are smarter than that. So more plates equal more holding, and they are not more likely to break.

 

[BrooklynBay]

CDW6212R mentioned earlier on the top of this thread something about Kolene steels, and blue frictions. What type of material is this, and who sells them?

 

[Glacier991]

Homework. Try google and Kolene.

Ok here's a gimmee. ALTO makes em.

 

[BrooklynBay]

There is a website called WWW.Kolene.Com that has some information, but I didn't see anything about transmission parts. Another one that I was looking at was WWW.AltoUSA.Com/Kolene.Htm with a lot of information on what I was looking for. Here is what the home page on Kolene said: Kolene Steel
Kolene® is a salt bath nitriding process. In generic terms, it is a thermochemical diffusion process, whereby ferrous parts are processed in molten salt with a specific nitrogen potential. In plain English, it provides a surface treatment that enhances wear and fatigue resistance from 200% to 500%.

Kolene® plates are higher heat resistant and offer increased lubricity.
Kolene® is a registered trademark of Kolene Corporation.

 

[sparky2263]

The reason the older 3 speeds seemed to last longer is solely due to the fact that they were 3 speeds. Cars didn't get as many miles, get loaded or driven as hard. As we have become more of a mobile and demanding society, we have come to expect more and more out of our vehicles.

We regularly rebuilt 2 and 3 speeds before they hit 100k miles. Nobody squawked about $200-300 back then though. Now that it's $1500 and up, it hurts a bit more.

 

[Green98XLT]

Don't forget that nowdays people want their auto trannies shifting seamlessly = lots of slipping.

The old 3 speed autos like the C4 and C6 shifted good and positively engaged on upshifts, the new 5r55 in my Ex shifts so damn smooth that you can hardly tell it's upshifting. I personally hate that! But the millions of blue hair grannies that buy Explorers want nothing but smoothness or they are back at ford with a warranty.

 

[Glacier991]

Good point. In fact, the 5R55E "PROGRAMS" some controlled slippage into the computer that applies the clutches, bands and torque convertor for JUST that reason(!)

 

[BrooklynBay]

You could always install a shift improver kit, and reprogram it to have more pressure if you want a firmer shift, but don't touch the EPC solenoid's set screw!

 

[BrooklynBay]

So is it always better to go with the Kolene than with Kevlar? Maybe some work better on one kind of transmission, but not on another. The transmissions that were designed to work with V8s probably have more line pressure, so it would have more apply force. In that case maybe then the Kevlar is better. What about if you have a high ratio boost valve, and other modifications to increase the apply pressure? Would the Kevlar work better then? If it doesn't, why would they manufacture it?