B2 piston BS - PeachParts Mercedes-Benz Forum

Blazemaster · #1 11-30-2015, 07:12 PM

Hi there, new to the forum. I recently bought a 1985 300d from my best friend. The transmission went out for him while he was at a stoplight and he sold it to me cheap. He is a busy guy so he didn't want to try and fix it. He said he came to a stop and when he started moving again there was a little jolt, and no more forward movement.

The car is in amazing shape so I want to figure this out. Reverse still works so I decided to try the b2 piston. While I was down there everything looked normal except the black rubber seal for the b2 piston, it was toast. It also had the original aluminum sleeve. I replaced everything and did a k1 spring kit while I was there.

In the end it wasn't as hard of a job as I first pictured but it didn't fix my problem. Still no forward movement. The b2 brake band seemed intact to me, it sprung back when force was applied and seemed to work smooth. Other than that I am stumped.

Should I start looking for another transmission?

I have also read you can get a longer pin that goes from the brake band to the piston. I have a machine shop, any reason I can't just make one a bit longer, or would that even have a chance of helping?

If not I think I can get a used trans, but it's $400, and about 400 miles away. Also I have never replaced a trans, but I'm sure I could. How big of a job is it without a lift?

Thanks!

leathermang · #2 11-30-2015, 09:23 PM

Use the search feature to check out Trans-x first....
cheap, might help, no harm if it does not help...
use my name in the search to find the best posts.....LOL

Stretch · #3 11-30-2015, 09:38 PM

Quote:

Originally Posted by Blazemaster

Hi there, new to the forum. I recently bought a 1985 300d from my best friend. The transmission went out for him while he was at a stoplight and he sold it to me cheap. He is a busy guy so he didn't want to try and fix it. He said he came to a stop and when he started moving again there was a little jolt, and no more forward movement.

The car is in amazing shape so I want to figure this out. Reverse still works so I decided to try the b2 piston. While I was down there everything looked normal except the black rubber seal for the b2 piston, it was toast. It also had the original aluminum sleeve. I replaced everything and did a k1 spring kit while I was there.

In the end it wasn't as hard of a job as I first pictured but it didn't fix my problem. Still no forward movement. The b2 brake band seemed intact to me, it sprung back when force was applied and seemed to work smooth. Other than that I am stumped.

Should I start looking for another transmission?

I have also read you can get a longer pin that goes from the brake band to the piston. I have a machine shop, any reason I can't just make one a bit longer, or would that even have a chance of helping?

If not I think I can get a used trans, but it's $400, and about 400 miles away. Also I have never replaced a trans, but I'm sure I could. How big of a job is it without a lift?

Thanks!

The point about the longer pin (or different length pins) is that it is (or they are) used to set the correct clearance between the band and the drum.

Just making the pin longer isn't necessarily the correct thing to do with out measuring the clearance.

Measuring is everything.

Ideally you should be measuring the hydraulic pressures and then comparing the values you get with the data in the hard to find chapter 27 of the factory service manual. (Alternatively this thread has some data that might help => DIY W123 Transmission Diagnose and Adjustment 722.xx OM 616-7 - Mercedes-Benz Forum )

#####

As for transmission removal

I'm of the opinion you are better off removing the engine and transmission in one go rather than struggling trying to pull the transmission from out under a car on axle stands.

Blazemaster · #4 11-30-2015, 09:52 PM

Thanks for the replies so far. I have a feeling an additive is not going to help in this case. The car has over 420k but has always been garaged, and taken to the dealership for repairs. I can't afford that treatment so I will have to do it myself.

Sounds like a newer trans is in the books. I really didn't want to do that lol.

As far as removal, I am not sure which route I would go. If I don't remove the engine/trans as a unit I have to deal with the car on jackstands. If I do, there is a lot more to remove and I have to do all the fluids as well.

Stretch · #5 12-01-2015, 05:04 AM

Quote:

Originally Posted by Blazemaster

Thanks for the replies so far. I have a feeling an additive is not going to help in this case. The car has over 420k but has always been garaged, and taken to the dealership for repairs. I can't afford that treatment so I will have to do it myself.

Sounds like a newer trans is in the books. I really didn't want to do that lol.

As far as removal, I am not sure which route I would go. If I don't remove the engine/trans as a unit I have to deal with the car on jackstands. If I do, there is a lot more to remove and I have to do all the fluids as well.

In my experience an additive is a waste of time and money. Of the Mercedes transmissions I've taken to pieces the majority of the gunk that stays in a transmission after a drain and refill is in the valve body and as that part is a no-flow / extremely low flow hydraulic system the only way to remove junk is to take it to pieces and physically remove it.

##########

From your description I get the impression something is broken. If I were in your shoes I would be making some hydraulic measurements to see if I could identify what is wrong. (Knowing me) I would then quickly get to a stage where the valve body would be removed and I'd be looking for evidence of scoring or damage on the B2 brake drum...

##########

If going down the "unknown second hand transmission is better than what I've already got" route then I seriously would not piss about under a car on axle stands trying to remove a 722.3 transmission. The chances of damaging yourself the transmission(s) or the car are quite good!

leathermang · #6 12-01-2015, 10:34 AM

Quote:

Originally Posted by Stretch

In my experience an additive is a waste of time and money. Of the Mercedes transmissions I've taken to pieces the majority of the gunk that stays in a transmission after a drain and refill is in the valve body and as that part is a no-flow / extremely low flow hydraulic system the only way to remove junk is to take it to pieces and physically remove it.
..... The chances of damaging yourself the transmission(s) or the car are quite good!

' no or low flow hydraulic system' ... but the transmission WORKS on those hydraulic flows for all its important functions.. causing the proper bands to tighten on the proper clutches ...
'waste of time' ... NOT MUCH TIME... a few hours which MIGHT fix something...
'waste of money' ... NOT MUCH MONEY...perhaps $30-40 and part of the cost involves changing out the old fluid and filter... something few would argue is a bad thing anyway...
Really not much sensible argument against trying it given the much larger next steps on your list.

Blazemaster · #7 12-01-2015, 11:07 AM

I appreciate the responses. I was leaning towards dropping the trans by itself until I read Stretch's response.

Is it really that hard? Don't mean to start an argument, but I have read quite a few threads where folks have done it without too much hassle. I can't imagine the 722.3 weighs more than 250-300 lbs.

I have lots of cribbing, four 6 ton jackstands and a 4 ton long reach jack with a large plate to cradle the trans. I wish I had access to a lift but that's just not an option. I do have a large 3 ton engine hoist but I really would rather not remove the engine unless I have to. It seems like I would need the car up on jackstands to remove the engine anyways, why not just do the trans itself?

I work in a machine shop, and deal with thousand lb.+ items daily. I have rebuilt large machine tools that have heavy, precise parts. I am good with mechanical stuff but I just don't have a ton of auto experience yet. I have never removed an engine or trans.

Again just trying to have a friendly discussion, let me know your thoughts. Thanks!

EDIT: It has fresh trans filter and fluid

Stretch · #8 12-01-2015, 11:36 AM

Quote:

Originally Posted by Blazemaster

I appreciate the responses. I was leaning towards dropping the trans by itself until I read Stretch's response.

Is it really that hard? Don't mean to start an argument, but I have read quite a few threads where folks have done it without too much hassle. I can't imagine the 722.3 weighs more than 250-300 lbs.

I have lots of cribbing, four 6 ton jackstands and a 4 ton long reach jack with a large plate to cradle the trans. I wish I had access to a lift but that's just not an option. I do have a large 3 ton engine hoist but I really would rather not remove the engine unless I have to. It seems like I would need the car up on jackstands to remove the engine anyways, why not just do the trans itself?

I work in a machine shop, and deal with thousand lb.+ items daily. I have rebuilt large machine tools that have heavy, precise parts. I am good with mechanical stuff but I just don't have a ton of auto experience yet. I have never removed an engine or trans.

Again just trying to have a friendly discussion, let me know your thoughts. Thanks!

EDIT: It has fresh trans filter and fluid

I think if you have a lift and a transmission jack (in other words the proper tools for the job) then you're best off doing it from under the car.

I reckon the most miserable way to do this job with out the lift and the transmission jack is on axle stands for the reasons I stated previously.

Diesel911 · #9 12-01-2015, 06:11 PM

Quote:

Originally Posted by Blazemaster

I appreciate the responses. I was leaning towards dropping the trans by itself until I read Stretch's response.

Is it really that hard? Don't mean to start an argument, but I have read quite a few threads where folks have done it without too much hassle. I can't imagine the 722.3 weighs more than 250-300 lbs.

I have lots of cribbing, four 6 ton jackstands and a 4 ton long reach jack with a large plate to cradle the trans. I wish I had access to a lift but that's just not an option. I do have a large 3 ton engine hoist but I really would rather not remove the engine unless I have to. It seems like I would need the car up on jackstands to remove the engine anyways, why not just do the trans itself?

I work in a machine shop, and deal with thousand lb.+ items daily. I have rebuilt large machine tools that have heavy, precise parts. I am good with mechanical stuff but I just don't have a ton of auto experience yet. I have never removed an engine or trans.

Again just trying to have a friendly discussion, let me know your thoughts. Thanks!

EDIT: It has fresh trans filter and fluid

When I pulled the Trans on my Chevy Astro Van I broke down and bought a Harbor Freight Transmission Jack. It helped the job out a lot. I had previousl done that sort or thing with regular Floor Jacks.
Note the Jack is manual and has a aperture for a 1/2" Drive Socket Wrench. The top plate can be tilited at an angle but there is not a lot of range to it and it is even more manual having a screw and wing nut on each side and slots that allow the top plat to tilit.
The Jack is on 4 each 2 inch Plastic Wheels.

In my case the Van already sat high off of the ground but I put suitably sized wooden Blocks under the Wheels to raise it even higher.

The possible problem with raising the Vehicle high is that the Jack only has soo much upward rang to it.

I pulled the Trans with the Engine in the Van.

However, I did have to tilt the Engine/Transmission assembly a bit just a bit before I disconnected the Trans. Also on the Van there was lots of room as the transmission does not sit in a tunnel.

I forgot to mention once the Trans is out and you crank the Jack down it is possible for the height of the whole thing to be too high to roll it out from under the vehicle.
I pushed the trans off of the Jack onto a piece of Wood and drug it out from under the Van.

I think having the vehicle on Wooden Blocks is safer then having it on Jack Stands but of course it depends on the size of the Blocks and how hight the stack of them is.

chasinthesun · #10 12-01-2015, 06:34 PM

Did you locate the instructions from diesel giant ,he actually describes w/pictoral on how to properly install the b2 piston ,he also failed on his first attempt to install it correctly and had to go back in to reinstall, something about a pin hitting a certain way ,he describes this detail.

leathermang · #11 11-30-2015, 10:13 PM

Trans-x bottom line is that it is a subtractive ...taking out the built up varnish in the tiny passages which control the activation of the clutches in the transmission...
.....

Diesel911 · #12 12-01-2015, 10:52 AM

When I first had B2 piston symptoms changing the AT filter and fluid got it to work.

After that just less then 1 year later the B2 Piston broke.

leathermang · #13 12-01-2015, 11:01 AM

Hydraulic cylinders work by having hydraulic fluid sent to them.. it pushes on the internal piston... some have loads which will cause them to retract if the pressure is cut off.. some require fluid to be inserted on the other side of the piston to have it retreat...
The ' valve body ' is just a bunch of holes directing the fluid in the proper tubes at the proper time to move the pistons which cause the clamping pressure of the friction material on the clutches ... on automatic transmissions this is usually from the side...
It is important that they work at the speed designed to work...and at the time relative to the other clutches they are designed to work... and clogged orifices due to years of built up varnish are a clear impediment to that functioning.

leathermang · #14 12-01-2015, 11:26 AM

The most important thing for safety and ease in pulling a trans...
is having the car High enough.... so the height of the trans PLUS the height of the rolling floor jack allow the trans to be pulled out from under the car with no interference...
and LEVEL with the ground....
thus once you get the bolts holding it on off... you can ROLL it back from the engine LEVEL... not putting any pressure on the main shaft.... or binding...
so a properly positioned rolling floor jack along with a level car to start with...
makes it pretty ' easy ' and safe...

BillGrissom · #15 12-01-2015, 03:13 PM

If you do swap or rebuild the tranny, yours is a 722.4xx, unlike the 722.3xx in 1982-84 300D's. At least true for CA 1985, but I recall for all 1985 300D/SD/TD/CD. You could probably fit an earlier tranny, but the later one is probably preferred. One difference I know is the neutral safety switch and mating plug. In a related note, your 1985 has the better rear-end w/ taller gear for lower rpm's on the highway.