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4R70W Rebuild Diary - Part 3 - Bearings/thrust washers

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Glacier991

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This is part 3 of a series. Part 1 is here:
http://www.explorerforum.com/forums/showthread.php?t=128800

Part 2 is here:
http://www.explorerforum.com/forums/showthread.php?t=157283

Every transmission has internal tolerances... end to end. These are controlled by what are called "thrust washers" and by actual bearings... known as "torrington bearings". The 4R70W has 7 torringtons... impressive.

In my mind torrington bearings equal longevity and durability.

So here are the torringtons..... as I said... 7 is awesome. Here they are

DSCN6610.JPG


And the master list:

DSCN6611.JPG


each individual packet has its own description

DSCN6612.JPG


There are a few "thrust washers", and some plastic (!) "selectives" used to set end play that we will look at as well... and a least one bronze thrust washer... but for now you get the idea. I will also add a sidebar about torringtons.

My advice is, although you may feel like a kid at Christmas when you get your torringtons, DO NOT open them until it is time to use them. Some are seemingly alike.... avoid being confused. Oh, I also dip mine in ATF prior to use as startup lubrication.
 




Glacier991

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Plastic Selective Thrust Washers

Most transmissions use thrust washers of varying thicknesses to adjust internal case end to end clearance. Often these are bronze, but in the case of the AOD and 4R70W they use some plastic ones. Yes, you heard me, plastic. Before you go nuts.... remember these are pieces that adjust the ability of the guts to slide front to back... they do not bear much weight. Plastic is more and more being used in bearings believe it or not. Plastic has its own inherent lubricity (eg. teflon as an example).

Here is the range of selectives. No this is not some olympic statement.

DSCN6649.JPG


These run from about .110 thick on the left to .056 or so on the right as I recall.

I'll show you more as we assemble this transmission
 




Glacier991

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Torrington Sidebar

I showed you some torrington bearings. let's talk briefly about them.

I have no idea where they got their name, but will assume some fellow invented them and got his moniker attached for that.

What they do is allow the use of a true roller bearing in pretty tight quarters. They have more and more replaced thrust washers, which are usually bronze and rely on a film of oil for their slipperiness to be replaced with something more durable. We saw how the A4LD, as it morphed into the 5R55, started using torrington bearing or torrington style bearings, almost everywhere. result? Less mechanical failure.

Let's look inside one. Believe it or not most of these little guys usually snap right apart, spilling their secrets (but not all snap right apart, as you will see in the Diary). Using a knife edge or a thin screwdriver will pop apart the two shell halves on those without the halves secured to one another. What is inside?

DSCN6644.JPG


A carrier with needle roller bearings around it.

The two halves snap together, with the needle carrier and rollers inside. Here is one half, you can see how it is set up to snap together wth a top mating half

DSCN6646.JPG


Here is the roller carrier added

DSCN6647.JPG


and finally the top. Thumb pressure in the inner hub area produces a distinct "snap" as the two halves go together.

DSCN6648.JPG


So now you know the secrets of the mysterious "Torringtons". They are easy to clean on the ones that snap open.

A question was posed, which side is UP? The answer is ..."it depends". In the general case, there is no top or bottom. BUT... since they need to be retained concentric to whatever rides on them and rotates, SOMETIMES there are lips or fingers molded into one or other case half to go a certain place. It will be intuitive. Example.... the rear case torrington in this tranny has a lip that goes over the bushing part of the case to hold it in place this properly. You could not install it wrong.

Cost. From FORD, per each these babies can go for over $20. Sonnax sells the SET of 7 for the 4R70W for under $40. Moral... when possible buy in sets!

I hope this little "sidebar" helped.

Part 4 continues here:

http://www.explorerforum.com/forums/showthread.php?t=157428
 




Glacier991

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If you have questions, comments, ideas or just feel an overwhelming need to post about this thread, please go here ...

http://www.explorerforum.com/forums//showthread.php?t=161450

I am trying to make it easy for folks just wanting basic information. The questions etc can have their own thread. Thanks for understanding.
 




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