B2 brake band replacement - PeachParts Mercedes-Benz Forum

tbomachines · #1 06-18-2011, 05:33 PM

Good afternoon. After toiling away in the sun for 5 hours I've determined that my B2 BAND is broken. I initially thought it was the piston, but upon removal the piston looked fine, with normal wear. When I replaced the piston the first time, I remember there was a LOT of tension on the thing, pushing it outward. This time there was none, the B2 freely went in and out, along with the doggy bone pin. My guess is that the B2 band is broken, since there was no springing motion against the piston, please correct me if I am wrong!! because I want to do this right the second time.

Next question is, can the B2 band be replaced with the trans still in the car? It seems possible since it is far enough back and accessible from dropping the pan and whatever valve/spring assembly is right on the back of it. Anyone have any experience with this? I am extremely hesitant to take the entire trans out because I am about 250 miles away from home, and the car is sitting in my friends' parents' driveway, they have been very gracious to me and let me work on the car there while it is out of commission. In other words, I do not have the capability to yank the engine/trans out.

tbomachines · #2 06-18-2011, 05:38 PM

I should also add, no flakes in the pan, nothing out of the ordinary. Fluid looked fine, as I flushed about 15k mi ago. I put it all back together, added fluid again and put it in drive hoping in the off-chance that it was the piston being stuck--small click and no movement (I had repositioned the band "receiver" and the dog bone, I suspect it just knocked it out of place again).

Diesel911 · #3 06-19-2011, 12:43 AM

See post #7 for claimed $63 B2 Brake Band.
B2 Piston Woes (maybe)

whunter · #4 06-19-2011, 01:56 AM

Quote:

Originally Posted by tbomachines

Good afternoon.
After toiling away in the sun for 5 hours I've determined that my B2 BAND is broken.

I initially thought it was the piston, but upon removal the piston looked fine, with normal wear.

When I replaced the piston the first time, I remember there was a LOT of tension on the thing, pushing it outward.

This time there was none, the B2 freely went in and out, along with the doggy bone pin.

My guess is that the B2 band is broken, since there was no springing motion against the piston, please correct me if I am wrong!! because I want to do this right the second time.

Next question is, can the B2 band be replaced with the trans still in the car?

It seems possible since it is far enough back and accessible from dropping the pan and whatever valve/spring assembly is right on the back of it.

Anyone have any experience with this?

I am extremely hesitant to take the entire trans out because I am about 250 miles away from home, and the car is sitting in my friends' parents' driveway, they have been very gracious to me and let me work on the car there while it is out of commission.

In other words, I do not have the capability to yank the engine/trans out.

1982 300SD or 1990 300E ?

The brake band can NOT be replaced in the car.

It requires removing the clutch packs to access.

.

whunter · #5 06-19-2011, 01:59 AM

Quote:

Originally Posted by tbomachines

I should also add, no flakes in the pan, nothing out of the ordinary.

Fluid looked fine, as I flushed about 15k mi ago.

I put it all back together, added fluid again and put it in drive hoping in the off-chance that it was the piston being stuck--small click and no movement (I had repositioned the band "receiver" and the dog bone, I suspect it just knocked it out of place again).

FYI: There are two dog bones on each brake band = one on the reaction valve and one on the B2 piston.

tbomachines · #6 06-19-2011, 02:25 AM

Thanks for the info guys! I'm not sure I trust that $85 (used to be $63) band, I am a full supporter of PP and I highly doubt Phil would match that price, seems too good to be true for a new band from the other supplier but I guess I'll give them a call and find out what the deal is, just very loyal to the forum. Man, I just had the engine and transmission out last August to complete the swap too

. I've been toiling over about 300 pages of german FSM trans repair for the last 6 hours and I still don't have a very good grasp on it.

tbomachines · #7 06-19-2011, 02:28 AM

Quote:

Originally Posted by whunter

1982 300SD or 1990 300E ?

The brake band can NOT be replaced in the car.

It requires removing the clutch packs to access.

.

This is the 300SD--sorry, should have mentioned that in the first post!

whunter · #8 06-19-2011, 03:10 AM

Mercedes-Benz 722.3 / 722.4 Automatic Transmission ATSG Rebuild Manual - Softcover
http://www.auto-repair-manuals.com/Mercedes-Benz-722-3-722-4-Automatic-Transmission-ATSG-Rebuild-Manual.html

BoiseBenz · #9 06-19-2011, 03:12 PM

Quote:

Originally Posted by whunter

Mercedes-Benz 722.3 / 722.4 Automatic Transmission ATSG Rebuild Manual - Softcover
http://www.auto-repair-manuals.com/Mercedes-Benz-722-3-722-4-Automatic-Transmission-ATSG-Rebuild-Manual.html

Good book but useless to you now. B2 is first in last out from front of transmission.

In theory if you tow the car engine running up to about 35 mph and shift into drive it should engage fourth, which only uses k1 and k2 clutches and neither band. Then just don't slow below 25 on the trip home. Hah!

Stretch · #10 06-19-2011, 03:36 PM

Quote:

Originally Posted by tbomachines

Thanks for the info guys! I'm not sure I trust that $85 (used to be $63) band, I am a full supporter of PP and I highly doubt Phil would match that price, seems too good to be true for a new band from the other supplier but I guess I'll give them a call and find out what the deal is, just very loyal to the forum. Man, I just had the engine and transmission out last August to complete the swap too

. I've been toiling over about 300 pages of german FSM trans repair for the last 6 hours and I still don't have a very good grasp on it.

Oh wow I didn't know that the German versions have the transmission chapter... is that hard copy or on a CD?

Anyway if you want a nice exploded parts view have a look here:-

http://www.ganzeboom.net/images1/ganzeboom/parts/Mercedes/722.3,%20722.4.pdf

This doesn't tell you about the torque specifications and limits of the parts when fitted of course but it shows where most of the stuff goes.

I found their equivalent 722.1 pdf pretty useful for taking my 722.1 transmission apart.

As for the brake band - it could be broken - but bear in mind it probably won't move all that far... we're talking a few mm not cm. If it doesn't spring back - well that's something else.

Good luck

tbomachines · #11 06-19-2011, 04:14 PM

Quote:

Originally Posted by Army

Oh wow I didn't know that the German versions have the transmission chapter... is that hard copy or on a CD?

Anyway if you want a nice exploded parts view have a look here:-

http://www.ganzeboom.net/images1/ganzeboom/parts/Mercedes/722.3,%20722.4.pdf

This doesn't tell you about the torque specifications and limits of the parts when fitted of course but it shows where most of the stuff goes.

I found their equivalent 722.1 pdf pretty useful for taking my 722.1 transmission apart.

As for the brake band - it could be broken - but bear in mind it probably won't move all that far... we're talking a few mm not cm. If it doesn't spring back - well that's something else.

Good luck

I had it saved on my computer from when I replaced the B2 piston

. I've got a few manuals that I've been able to dig up online but still have to read through them (going to be a busy week...).

Quote:

As for the brake band - it could be broken - but bear in mind it probably won't move all that far... we're talking a few mm not cm. If it doesn't spring back - well that's something else.

What do you mean by that? Isn't the B2 band basically a big circular spring (kind of like those spring-type hose clamps) lined with material? In other words, if it breaks, there will be no tension. I am able to move the dog-bone receiver (on piston side) a few cm up and down.

Stretch · #12 06-20-2011, 12:28 PM

Quote:

Originally Posted by tbomachines

...

What do you mean by that? Isn't the B2 band basically a big circular spring (kind of like those spring-type hose clamps) lined with material? In other words, if it breaks, there will be no tension. I am able to move the dog-bone receiver (on piston side) a few cm up and down.

All I can really say - for my 722.1 brake bands that yes they are spring-like but they are only really noticeably springy when you compress them out of the 'box. For the distance that they move in the gearbox I think (and only think!) that it would be difficult to notice any great movement. But I'm not saying it is impossible...

...look I'm not being really clear here I know - but think of the amount of clearance you get on W123 parking brake drums (or on any other drum brakes). If you were to poke a stick through a hole in a brake drum onto a brake shoe, would you find it easy to tell if the brake shoe was being properly sprung back? I think you'd probably have to meet a few of them before you could tell for sure - don't you?

Brake bands - like brake shoes - sit very close to the drum.

I know this doesn't help much. You might find that the band is broken or cracked - but the only way you are going to tell for sure is to take the gearbox apart and see.

rs899 · #13 06-20-2011, 12:39 PM

^^ I agree. It seems academic. There's no way to replace the band w/o pulling the trans and unless it's in the piston you are going to have to pull it anyway...