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4R70W Rebuild Diary - Part 6 - Bands

Glacier991

EF Tranny Guru
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1992 XLT
The 4R70 only utilizes TWO bands. One for the reverse servo, and one for the OD servo. It has been said before but I will say it again..absent major grenading of the transmission the reverse band at least, ought to be reuseable. A transmission with a lot of metal floating in the fluid can ruin that band for reuse. The OD band probably is equally reuseable... but the replacement is cheap, and you MIGHT want to consider newer band materials - Kevlar or Carbon Fiber.

Let's take a moment to talk about automatic transmission friction material... clutch or band, it's pretty much all the same. People want to tend to think about brake pads as they think about AT frictions. Not a good comparison. The AT is a wet environment for frictions - huge difference. In truth, properly cared for the friction linings in an AT really do NOT have a "useful life"!... they can practically go on forever. If you tear into a 250,000 mile tranny that is healthy but for hardened seals... you may find perfectly good frictions at practically brand new thicknesses!

The reverse band is cast iron. Brick shjthouse territory. In a healthy tranny the band will be generally fine as will it's friction material

Let's talk Kevlar. I am not an advocate nor am I am opponent. I am not convinced...but when it starts showing up as the "best thing" in HP applications, and outfits like Raybestos start offering it.... well I am going to wade into the shallow end of the pool and use a Kevlar OD band. [Edit... maybe...]

The latest craze is carbon fiber. I like the idea better than Kevlar but as I add this comment I do not as yet have any personal experience with it.

Reverse band seems like overkill for Kevlar, but I DO have one (I told you I investigated everything I could).

Let's look at the Reverse band... a typical cast iron double wrap variety... stock and new in this pic...

DSCN6666.JPG


another view.... notice the band is in 3 pieces....

DSCN6667.JPG


The outer two apply together and the 3rd in the middle applies separately but simaltaneously.

Another look at the band itself

DSCN6669.JPG


The friction material is rather thin... I tried to capture how thin... without much success because a ground bevel tended in pics to look like the material. I took one pic and drew a little arrow to show the edge of the friction material itself.

DSCN6671.JPG


Not very thick.

I also had a reverse band with Kevlar on it. It is mainly to the eye just a different color, but for grins here it is...

DSCN6672.JPG


and another pic

DSCN6673.JPG


On this build I plan to go stock, unless someone buys it and tells me otherwise. Stock band is FORD P/N FOAZ-7D095 - A and lists for $26.62.

OD BAND

This band is a single wrap band. Stock is P/N F2TZ-7F196 - A and lists for $13.70. I bought an aftermarket Kevlar for about $20. Here it is...

DSCN6676.JPG


And to make you know, they emblazon it with the logo!

DSCN6678.JPG


The anchors are pretty stout things...

DSCN6677.JPG


DSCN6679.JPG


A good soaking in ATF and these will be ready.

Bands! Thread is done. Comments welcome.

The Diary, Part 7, Planetary and Sun Gear, continues here:

http://www.explorerforum.com/forums/showthread.php?t=157487
 




Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,832
Reaction score
33
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
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...ad.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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