My Superior Shift Kit thread (W124 300DT)

[iandiam]

Would it behoove me to wipe the colored paint from the springs in the kit before I install them?

I'm going out to get the ATF to replace right now, and I was hoping to install the large springs today as a start...

[gsxr]

I thought the paint on the springs helped identify them...? If so, I'd leave the paint on. If not... nevermind.

[iandiam]

The colors are referred to in the instructions. I am a one-step-at-a-time kinda mechanic, and as I have never ventured into replacing transmission parts, I only pulled one plate at a time.

I did soak the paint off in kerosene first, however, then ultrasonic-ed them, dried, them well, and lubed 'em up with ATF. I figure the less particulate crud, however microscopic, the longer the tranny life. If I had pulled the VB or done any of the B-springs, I would have done it, too, just slowly, carefully, and methodically...All the OCDers know what I mean...

Replacing just the K1 and K2 accumulator springs has fixed the problem. Like magic. What an easy job...an offset hollow-ground flathead, a 13mm ratchet, and a 5mm allen head. Lather, rinse, repeat...

Third runs up to about 4200+ now, however...I THINK that should be normal at WOT, but there's no more rubber smell on highway 3/4s, no neck-snapping shifts, and the vacuum is turned all the way up to 13hg inches...

Thanks for all the help, everybody, some posthumously. I'll report back on the new 0-60 run later tonight!

[rkpatt]

Besides K1 and K2 springs , which others can I replace with the Superior shift kit springs without pulling the valve body ? - Tahnks

[tangofox007]

Originally Posted by rkpatt

Besides K1 and K2 springs , which others can I replace with the Superior shift kit springs without pulling the valve body ? - Tahnks

The B-1 spring train, on the front of the valve body. Everything else requires removal of the valve body. There are several springs that can be installed without separating the halves, but access is blocked at the rear with the valve body in place.

Removing the valve body is not much of a problem. Separating the two halves is another story.

I can email you a copy of the kit instructions if that would help.

[Oldwolf]

I’ve had my 300D long enough now and am comfortable enough with it to start tackling the shifting issues I am having with my 722.4 transmission. Rather than starting another thread, I am hoping that continuing this one will go further in documenting corrective actions for the 722.4.

These are my symptoms.

Cold Engine and Transmission-
Light throttle, Harsh 1-2 shift at high rpm, Flaring 2-3, 3-4
Heavy throttle, Good shifts all gears.

Hot Engine and Transmission (maybe 15 minutes of driving)-
Good shifting at all loads and RPM ranges, no complaints.

I have replaced the filter and fluid but this shifting pattern stayed the same.

I plan to follow gsxr’s recommendation of verifying the vacuum system first. First I’ll replace any bad tubing and then check/adjust the VCV according to the FSM.

The FSM states that the vacuum should be 420 mbar for my 602 engine application. Am I correct that higher than the spec can cause flaring?

Also, I don’t understand the comment “When engine is switched off, move accelerator to full-load stop. Specification: 0 mbar …”. Wouldn’t the vacuum drop to 0 on its own once the engine is off?

Thanks for the help!

gsxr:

Great info, thanks for sharing!

Now, I may be a little late to the party... but one major item has been overlooked here. The transmission shift point (controlled by the control cable) and shift firmness (controlled by the vacuum signal) on the 1987-1993 300D are based ENTIRELY on throttle position. Why is this critical? Because if your engine power output is below normal (due to ALDA issues, or any of a dozen other reasons)... the tranny will shift like crap (often a late, high rpm, harsh shift). But there may be nothing at all wrong with the tranny, or springs, or anything else. Fix the engine power output, and the tranny problems may go away.

Also, make sure the VCV on the side of the injection pump is set correctly. This is not a "seat of the pants" adjustment, there is one proper setting, and you don't tweak it either way. (It can cause weird shift issues if this is mis-adjusted!) See the FSM for the official procedure (click here), but basically you loosen the mounting bolts, have a helper press the pedal to the floor (or pull the throttle cable to WOT), gently rotate the VCV (from full CCW turn it CW) until resistance is felt, then tighten down the bolts. Often it ends up right in the middle of the adjustment range. This is the FIRST step in correcting diesel tranny issues. The second step is making 100% sure that all the Tecalan vacuum tubing is intact and not leaking, along with checking the rubber fittings. Replace anything that is cracked, brittle, soft, or otherwise questionable. Then you have to fix the engine power output, particularly the off-idle power (generally fixed with ALDA adjustment).

When everything is set correctly, the transmission shifts should be butter smooth cold or hot, at light or medium throttle, with zero flaring. At WOT (kickdown) the shifts should be firm, and should occur at 4800rpm for each upshift. My '87 tranny has 300kmi on it, with all the original "K" springs (no Superior kit needed), and it shifts perfectly. But I've also spent a lot of time getting the engine power delivery correct (0-60 in 10 seconds), setting the VCV to spec, and replacing every vacuum tube & rubber hose in sight. Click here for a list of part numbers of the tubing and formed fittings, they are fairly cheap, it's a good idea to replace all of the old fossilized stuff.

Hope this helps!

[sixto]

Originally Posted by Oldwolf

Also, I don’t understand the comment “When engine is switched off, move accelerator to full-load stop. Specification: 0 mbar …”. Wouldn’t the vacuum drop to 0 on its own once the engine is off?

The step assumes you have an external vacuum source attached to the VCV. The VCV vacuum supply port should be isolated from the output port at full load stop. If you use a Mityvac on the supply port, a vacuum gauge on the output port shouldn't respond.

Sixto
87 300D

[gsxr]

Originally Posted by sixto

The step assumes you have an external vacuum source attached to the VCV. The VCV vacuum supply port should be isolated from the output port at full load stop. If you use a Mityvac on the supply port, a vacuum gauge on the output port shouldn't respond.

Sixto is exactly correct. You need an external vacuum source if you want to measure readings with the engine off, and you really don't want to do this with the engine running, unless you don't mind having your hands and face right on top of a motor spinning to 5000rpm (personally, I don't like that).

I use a venturi-type vacuum "pump", about $15 or so from Harbor Freight, but this requires a compressed air source to power it. Otherwise, a second vehicle (gas or diesel) will work for a vacuum source, just get a 10-foot length of vac hose from McParts, and hook it up to the other car to get a steady vacuum source.


Also - the FSM specs in mbar are kind of a pain to decipher. If you provide 15" (or more) of vacuum into the inlet of the VCV (located on the side of the IP), the output should measure 12-15" (approx) with the throttle at idle position, and this should smoothly decrease to zero vacuum at WOT. At least, that's what I measure on my cars, and mine all shift normally...

[Oldwolf]

I get it now. Thanks for the explanation. I do have a MityVac that I will try to use. The tip about the vacuum pump from Harbor Freight might come in handy if the MityVac doesn't have enough volume.

[gsxr]

The MityVac won't work. The VCV operates by bleeding off vacuum at a controlled rate... the MityVac simply can't produce enough volume. Either the HF venturi pump, or a second vehicle, will be required to supply the vacuum. Or, you can do it with the engine running.

Another option is to connect a vac gauge to the output of the VCV with a long length of hose, so you can view the vacuum while driving the car. And also disconnect the kickdown solenoid at the back of the tranny, and the Bowden cable. That will allow you to move the throttle between idle and WOT while driving, without the transmission downshifting.

[okcraig]

Quick question here I hope. I have a 420SEL and after reading this thread and other sites I ordered the Superior kit. I pulled the valve body today and started replacing the k1 and k2 springs. The k1 went with no problem, but the k2 has an issue. The designated springs in the instructions will not fit inside the accumulator. I sent an e-mail to where I ordered the kit from but thought I would check here as well. Am I missing something. The way I read the instructions, the pink spring should replace all of the other springs and plastic parts except for the accumulator itself. Is this right? TIA

[tangofox007]

Originally Posted by okcraig

The way I read the instructions, the pink spring should replace all of the other springs and plastic parts except for the accumulator itself. Is this right? TIA

The instructions call for using the red spring in "late models."

Did the original configuration consist of two springs or three springs?

[okcraig]

I was under told this was an early model but I could be wrong. It had three springs in the original configuration, however it didn't have any of the plasitc internal pieces.. I'll check to see if the red spring is narrower. However, the shorter blue spring still doesn't fit inside the accumulator. Thanks for your help.

I did go ahead and assemble it using the red spring and the original shorter spring in place of the short blue one. Unfortuneately once I got everthing together the transmission will not engage in any gear. Still checking it though. TIA

[tangofox007]

Originally Posted by okcraig

IUnfortuneately once I got everthing together the transmission will not engage in any gear.

There is a slot in the shift plunger that must be engaged when the valve body is reattached to the transmission.

[okcraig]

Tangofox007,

Thanks. Wouldn't you know it. Do I need to pull the valve body back off to do this? I'm assuming I do have to pull the pan again.