727 parts?

[Binder]

Hey guys, first post here so lets get the formalities out of the way....

1) vehicle model.
2) production date/or year model.
3) two wheel drive or four wheel drive.
4) type of transmission (and transfer case if applicable).
5) if 4x4, which axles front and rear.
6) which engine variation.
7) which ignition system variation.
8) which fuel system variation.
9) which brake system variation.
10) non-oem modifications present which May impact a response.

1)2005 s&n bravo
2)2005
3)4wd
4)727-205
5)60 f&r
6)first gen chev 350
7)ebl-TBI
8)ebl-TBI
9)4 wheel disk-GM half ton
10)basically everything on the vehicle is non oem but shouldn't effect this question.....

Ok now that that's out of the way I've lost reverse in my 727 and yet to pull the pan and see what the damages are. I know that there are a few common possibilities including possibly a broken reverse band. I'm tracking parts sources so when I get it open I can keep working rather than loose time chasing parts.....I've heard of a two piece flexible reverse band for a 727 designed to be installed without removing the transmission but I can't find where to buy one. I know this May or May not be the best way to fix this but the vehicle will get major teardown and maintenance in the next few months so I'd like to keepit together until then.
Anyone know where to get one of these two piece bands?
Thanks.

 

[Michael Mayben]

hey guys, first post here so lets get the formalities out of the way....

1)2005 s&n bravo
2)2005
3)4wd
4)727-205
5)60 f&r
6)first gen chev 350
7)ebl-TBI
8)ebl-TBI
9)4 wheel disk-GM half ton
10)basically everything on the vehicle is non oem but shouldn't effect this question.....

Ok now that that's out of the way I've lost reverse in my 727 and yet to pull the pan and see what the damages are. I know that there are a few common possibilities including possibly a broken reverse band. I'm tracking parts sources so when I get it open I can keep working rather than loose time chasing parts.....I've heard of a two piece flexible reverse band for a 727 designed to be installed without removing the transmission but I can't find where to buy one. I know this May or May not be the best way to fix this but the vehicle will get major teardown and maintenance in the next few months so I'd like to keepit together until then.
Anyone know where to get one of these two piece bands?
Thanks.

Never heard of, nor seen a "two piece" low/reverse band for a 904/727! Once they become two pieces, then you have exactly the issue you describe, loss of reverse gear!

The low /reverse band is one of the last items to come out the trans when performing an overhaul, and one of the first items to be installed using a replacement cast iron band.

If after removing the pan, you May find the low/reverse servo piston has "flopped" in it's bore resulting in loss of band apply. If that is the case, simply replacing it in proper position won't work in the long term, the case bore is now distorted slightly. The piston itself will also most likely have a microscopic crack in it which allows pressure bleedoff. So an aftermarket servo piston should be installed which offers more support in the case and solves the problem.

As far as "parts" are concerned, the B&M "transmission inna box" overhaul kit we sell is by far the most bang for the buck you will find for building a total upgrade 727. It includes all needed parts including premium frictions and both bands. And also a complete valve body reprogramming package including a 5.0 ratio kickdown apply lever.

B&M p/n is 10229, you must call the store to order, we don't show those in the online store yet.

 

[Binder]

never heard of, nor seen a "two piece" low/reverse band for a 904/727! Once they become two pieces, then you have exactly the issue you describe, loss of reverse gear!

Thanks for the reply. From what I've read the "two piece" band is intended to be installed in the trans without taking it out and tearing it down. I would imagine the end of the band where the attachment is comes off somehow.
If the band is broken and I can't find this part I'll look into rebuilds....
Thanks again.

 

[Binder]

Well good news, the band isn't broken. The strut broke and the servo snap ring came out but the servo stayed in so the servo and bore look to be fine. Now I need to find a good exploded view so I can make sure to get it all back together correctly.

 

[Binder]

Ok I found this picture in another thread here which tells me basically where the parts go. Now I can move my band around with my finger so it isn't attached at the other end away from the strut. Does the band just rest against this assembly or is it possibly broken too? Could I just rotate the band up against this end and install a new strut then adjust? Could it be this easy or is this just wishfull thinking on my part?
I'm sooooooooo happy that the band isn't broken so please don't shatter my new found joy!

 

[Michael Mayben]

The servo apply strut and piston left the scene due to excessive band clearance (meaning the band was nowhere near adjusted properly). That also means that the band is worn out and is lacking friction material. It is aggravated by banging the shifter back and forth forward/reverse/forward as in "rocking" to unstick a stuck rig and excessive engine rpm when doing so.

If the servo piston popped the retaining ring, then a tremendous force was exerted and I can't believe the retaining ring groove in the case bore is not distorted. No way I'd put that trans back together without using an aftermarket stabilized servo piston, it will do it again now as the bore is distorted.

If the low/reverse band is gone, then all friction materials in the kickdown band and both clutch packs are gone. If you don't perform a complete overhaul at this point, you are simply wasting time, oil, and risking damage to some irreplaceable parts.

Installing a replacement band in the case after the servo has been rebuilt can be real tedious in a bench build. I use forceps to install the strut in a precise location once all the other parts are positioned. Since the pic you posted is mine...I can assure you that even taking a picture that shows the strut/band/anchor detail is near impossible.

 

[Binder]

It is aggravated by banging the shifter back and forth forward/reverse/forward as in "rocking" to unstick a stuck rig and excessive engine rpm when doing so..

I assure you I don't do this though I am very hard on all parts in general.

if the servo piston popped the retaining ring, then a tremendous force was exerted and I can't believe the retaining ring groove in the case bore is not distorted. No way I'd put that trans back together without using an aftermarket stabilized servo piston, it will do it again now as the bore is distorted..

I do need to replace nearly all of the servo parts. The servo isn't stock as it was modified to install the art carr manual valve body. Iirc the aluminum part is original though. I'll likely just replace it all. Which aftermarket servo would you recommend?

if the low/reverse band is gone, then all friction materials in the kickdown band and both clutch packs are gone. .

Why do you say this? What does the reverse band have to do with the kickdown band and clutch packs?

if you don't perform a complete overhaul at this point, you are simply wasting time, oil, and risking damage to some irreplaceable parts..

I don't agree. You must have missed in my first post where I said the rig gets a complete teardown in a few months. Removing the transmission from this vehicle is extremely difficult so if I can make it work a few months then it's worth it even if I have to replace the trans in the end.

installing a replacement band in the case after the servo has been rebuilt can be real tedious in a bench build. I use forceps to install the strut in a precise location once all the other parts are positioned. .

But I'm not replacing the band....when I put the art carr valve body in I had this stuff apart but I don't remember the specific assembly. My only concern is the band attachment to the "strut" or whatever it's called at the other end. Using forceps sounds like a good idea though, thanks.

since the pic you posted is mine...I can assure you that even taking a picture that shows the strut/band/anchor detail is near impossible.

I did say the picture was from this site. Do you want me to delete it from my post?...I'm not looking for a picture of it but a expanded view of the assembly so I know I put it together right.
Thanks for your help.

 

[Michael Mayben]

I haven't missed anything in your original posts!

If one friction element is toast, all are gonna be toast. This "experience" comes from doing 727 transmissions commercially since 1969.

Any aftermarket replacement low/reverse servo is suitable, one is no better than the other. Brand name has nothing to do with this, the same servo system can be sold under several of the "performance" brands in a broad range of prices for the same item.

 

[Binder]

If one friction element is toast, all are gonna be toast. This "experience" comes from doing 727 transmissions commercially since 1969.

These parts very well could be worn but we can't know for sure without tearing it down further which isn't going to happen right now if I can help it.....from what I see in taking it apart this was all caused when the strut broke. When the strut broke the servo unrestricted slammed down against the spring which popped the snap ring out. Fortunately as this happened the servo didn't "flip" but it must have cocked very slightly which let the servo unseal and that's where it stopped. When I took the servo out the seal lip was folded over in one section. It May or May not have been out of adjustment but the strut is for sure in two pieces.....I'll get it all put back together and I'll keep you guys posted on how it holds up.
Thanks for the help!