It's B2 time!

[Strand]

As some of you may know, I've been dealing with a somewhat buggy transmission on my 84 300D for over a year now.

At first, it wasn't too bad. The initial post-purchase hesitation and erratic shifting patterns (as well as most of the flaring) were massaged out thanks to a thorough overhaul and adjustment of the vacuum system, and for a hot second it looked like the transmission was actually alright.

But the flaring wasn't fixed. Essentially, these were the symptoms:

• Car shifts into drive fairly quickly. The engagement isn't as firm as it is when shifted into reverse, but it's definitely noticeable and the car will creep.
• If light throttle is applied, the car behaves and shifts normally through the gears
• Under heavier acceleration, or when starting on an upward incline, the car would lose forward gear, leaving the engine to rev freely before eventually (sometimes) catching back into gear.
• Once the car gets into 3rd and moving faster than 25MPH, it's all smooth sailing.
• Reverse works perfectly.

Recently, things have gotten progressively worse to the point where the car is barely drivable: the transmission slips out of first with the slightest application of the throttle, and the drivetrain shudders a bit as it slowly catches 1st gear and builds up speed. If I lived in a flat, rural area with empty roads, I could potentially live with it, but it's just not an option in Brooklyn.

I've spent a LOT of time reading through all of the B2 related literature I could find in the past couple of days, and I'm 99% certain that my earlier assumption of a B2-piston failure is the cause of my problems. I'm assuming that it's the piston and not the band, as the car still engages forward drive, creeps, and reverses perfectly. And like before, once I'm in 3rd/going 25+, things are fine. All off this also seems to indicate that the transmission is not completely toast (fingers crossed!)

Everything I've read suggests that a failed band would result in no forward motion whatsoever--no engagement, no forward creep. For everyone who's more familiar with B2 issues than I am, is this correct? A snapped band would unfortunately put me in the market for a replacement transmission.

I've ordered the parts required for the piston job, and I'll keep everyone updated with further progress as we go along.

[Strand]

Parts list:

• 1072700432 - Band Piston, B2
• 1262770850 - Piston Bushing for Brake Band B2
• 0069977347 - Transmission Reaction Valve Seal
• 1262711180 - Auto Trans Oil Pan Gasket
• 1262770295 - Auto Trans Filter

Am I missing anything? Also--if anyone who's done this job would like to offer any additional knowledge that isn't included in the popular DIY guides, please feel free to share!

[Diesel911]

Originally Posted by Strand

As some of you may know, I've been dealing with a somewhat buggy transmission on my 84 300D for over a year now.

At first, it wasn't too bad. The initial post-purchase hesitation and erratic shifting patterns (as well as most of the flaring) were massaged out thanks to a thorough overhaul and adjustment of the vacuum system, and for a hot second it looked like the transmission was actually alright.


But the flaring wasn't fixed. Essentially, these were the symptoms:

• Car shifts into drive fairly quickly. The engagement isn't as firm as it is when shifted into reverse, but it's definitely noticeable and the car will creep.
• If light throttle is applied, the car behaves and shifts normally through the gears
• Under heavier acceleration, or when starting on an upward incline, the car would lose forward gear, leaving the engine to rev freely before eventually (sometimes) catching back into gear.
• Once the car gets into 3rd and moving faster than 25MPH, it's all smooth sailing.
• Reverse works perfectly.

Recently, things have gotten progressively worse to the point where the car is barely drivable: the transmission slips out of first with the slightest application of the throttle, and the drivetrain shudders a bit as it slowly catches 1st gear and builds up speed. If I lived in a flat, rural area with empty roads, I could potentially live with it, but it's just not an option in Brooklyn.

I've spent a LOT of time reading through all of the B2 related literature I could find in the past couple of days, and I'm 99% certain that my earlier assumption of a B2-piston failure is the cause of my problems. I'm assuming that it's the piston and not the band, as the car still engages forward drive, creeps, and reverses perfectly. And like before, once I'm in 3rd/going 25+, things are fine. All off this also seems to indicate that the transmission is not completely toast (fingers crossed!)

Everything I've read suggests that a failed band would result in no forward motion whatsoever--no engagement, no forward creep. For everyone who's more familiar with B2 issues than I am, is this correct? A snapped band would unfortunately put me in the market for a replacement transmission.

I've ordered the parts required for the piston job, and I'll keep everyone updated with further progress as we go along.

If the B2 band broke it would suddenly not work. Ususally that is the same with a broken B2 Piston.

As the B2 Band wears there could be a point where it would slip. When it slips could depend on temp and other things. There is several sizes of "Dog Bone" Thrust Pins to adjust. I believe the Valve Body has to be removed to do the measuerment correctly to do the adjustment.

B2 Pistons can be sticky and the Seal I assume can wear or get damaged and an intact B2 Piston might not function properly.

From the wear pattern on my B2 Piston it looked like the Aluminum metal Bushing behind the Seal had been grabbing or binding on the B2 Piston. The Replacment Bushing is made of Nylon.
I had slipping in first issues and changed the AT Fluid and Filter and the issue went away. Less then 1 year later the B2 Piston broke.

So there is a wide range of issues that could happen individually or in some mix together.

[Strand]

Originally Posted by Diesel911

If the B2 band broke it would suddenly not work. Ususally that is the same with a broken B2 Piston.

As the B2 Band wears there could be a point where it would slip. When it slips could depend on temp and other things. There is several sizes of "Dog Bone" Thrust Pins to adjust. I believe the Valve Body has to be removed to do the measuerment correctly to do the adjustment.

B2 Pistons can be sticky and the Seal I assume can wear or get damaged and an intact B2 Piston might not function properly.

From the wear pattern on my B2 Piston it looked like the Aluminum metal Bushing behind the Seal had been grabbing or binding on the B2 Piston. The Replacment Bushing is made of Nylon.
I had slipping in first issues and changed the AT Fluid and Filter and the issue went away. Less then 1 year later the B2 Piston broke.

So there is a wide range of issues that could happen individually or in some mix together.

Got it. We'll see what the exact issue is once the piston cover comes off!

[cooljjay]

Personally before jumping into this, I would check all your shift bushing, drain and replace fluid n filter with dex/merc fluid...Get the level at the right point...Then see where you are at....I would also check all shift linkage, vacuum and bowden cable. There is a lot that goes into making the transmission shift correctly....

[Strand]

Originally Posted by cooljjay

Personally before jumping into this, I would check all your shift bushing, drain and replace fluid n filter with dex/merc fluid...Get the level at the right point...Then see where you are at....I would also check all shift linkage, vacuum and bowden cable. There is a lot that goes into making the transmission shift correctly....

Thanks. Fluid and filter were both changed less than a month ago. The bushings, vacuum, bowden, modulator etc have all been checked as well.

[Strand]

Thoroughly unexciting update:

The B2 piston was broken, and has been replaced. The transmission now appears to be working fine.

[Diesel911]

Originally Posted by Strand

Thoroughly unexciting update:

The B2 piston was broken, and has been replaced. The transmission now appears to be working fine.

I hope you replaced the Seal and the Bushing also.

[Strand]

Originally Posted by Diesel911

I hop you replaced the Seal and the Bushing also.

Seal and bushing were both replaced. I didn't touch the orange o-ring (but it seems to be holding up).

[Strand]

On a potentially related note, I've noticed that the car doesn't seem to downshift (either for sudden acceleration or to maintain speed up a hill) unless I hit the kickdown switch. What gives?

[Diesel911]

Originally Posted by Strand

On a potentially related note, I've noticed that the car doesn't seem to downshift (either for sudden acceleration or to maintain speed up a hill) unless I hit the kickdown switch. What gives?

I have not read of this issue in the forum. There is a Governor inside of the tail of the Tramsmission (I have no idea what symptoms it would cause) and perhaps the Bowden Cable needs some adjustment.

[cooljjay]

Its a diesel....They lose power going up hills, thus the trans or operator needs to down shift....My auto takes longer then I like...thus I manually shift down or use the kick down....remember these autos can and are meant to be shifted like a manual....It also does the engine good to really rev up in a gear....knocks the carbon off...

Your driving a turbo so this shouldn't happen as much but this tells me you are having other deferred maintenance issues, such as alda, egr, rack damper, injection pump timing, injectors etc.....

Remember the transmission cannot tell when the engine isn't running up to spec thus when the engine is having maintenance issues it shows in the transmission...

[Diesel911]

Also very few people including myself have ever checked the AT pump prussure and the modulator pressure.