w126 tranny questions - Page 3 - PeachParts Mercedes-Benz Forum

Brian Carlton · #31 10-24-2007, 10:08 PM

Quote:

Originally Posted by hangit

Brian;

Since my modulator has a slow leak, will replacing it make any difference in my shifting? If I do replace it, what are the pressure settings for an 83 300SD?

Driving it tonight, downshifts are smooth, 1-2 is firm, 2-3 is ok, and 3-4 is marginal if I don't lead foot it.

John

Fixing the modulator leak won't make any difference. Just allows the vacuum pump a bit of a break.

It's the cap that needs replacement, most likely.

If 5" vacuum doesn't cut it, then an adjustment to the modulator is warranted.

hangit · #32 10-24-2007, 10:19 PM

Quote:

Originally Posted by Brian Carlton

Fixing the modulator leak won't make any difference. Just allows the vacuum pump a bit of a break.

It's the cap that needs replacement, most likely.

If 5" vacuum doesn't cut it, then an adjustment to the modulator is warranted.

My new cap will be here Friday. I'll bypass the EGR tomorrow and see if that improves anything. Friday I'll report if the cap makes a difference.

John

Brian Carlton · #33 10-24-2007, 10:23 PM

Quote:

Originally Posted by hangit

My new cap will be here Friday. I'll bypass the EGR tomorrow and see if that improves anything. Friday I'll report if the cap makes a difference.

John

The only thing those changes can do is to make your situation worse. So, be prepared for that outcome should it manifest itself.

hangit · #34 10-25-2007, 10:51 AM

Bypassing the 3/2 valves did nothing. What recommendations and who for a rebuilt tranny?

John

hangit · #35 10-25-2007, 04:02 PM

Attached is a picture of my modulator valve. I was all set to check pressures with the banjo bolt, but the 12mm bolt at the 4 o'clock position relative to the modulator does not seem to be the correct one. If it's the allen head flat bolt, that is much bigger than the ALDA banjo bolt. Please direct me to the right place. Thanks.

John

johntksr · #36 10-25-2007, 07:28 PM

I am sorry to hear that things have not improved following the 3/2 valve and EGR disconnect. I would continue to follow Brian's advice as he can talk you through the diagnosis. Fortunately for me, the disconnect of the 3/2, EGR and Bowden cable adjustment was just what the doctor ordered. I will be watching the post and hoping that you do not need to rebuild the tranny.

Good luck,
John

patbob · #37 10-25-2007, 08:44 PM

Quote:

Originally Posted by hangit

When I applied a vacuum to the modulator line, it did not hold. I have isolated the leak at the modulator

There's a little piece of rubber vacuum line connecting the hard line to the modulator down at the modulator. It could be the leak and is way easier to change than the modulator

Brian Carlton · #38 10-25-2007, 08:55 PM

Quote:

Originally Posted by hangit

Bypassing the 3/2 valves did nothing. What recommendations and who for a rebuilt tranny?

John

.........you're tossing in the towel already.........??

.........I'm not............

I didn't expect the 3/2 valves to do anything...........or make the situation worse.......so no surprise there.

hangit · #39 10-25-2007, 10:44 PM

Quote:

Originally Posted by patbob

There's a little piece of rubber vacuum line connecting the hard line to the modulator down at the modulator. It could be the leak and is way easier to change than the modulator

I checked the rubber tube, it's ok. The rubber cap is cracked and a new one will be Friday.

John

hangit · #40 10-25-2007, 10:47 PM

Quote:

Originally Posted by Brian Carlton

.........you're tossing in the towel already.........??

.........I'm not............

I didn't expect the 3/2 valves to do anything...........or make the situation worse.......so no surprise there.

No, I'm not giving up yet. I read through some of your other help posts to members with similar problems and noticed you advised them to turn the modulator adjustment 3 turns CW. I tried a half turn tonight and it improved the 3-4 flare, 1-2 a little firmer, no harsh downshifts. I will try another full turn tomorrow.

I'll post my results.

John

Brian Carlton · #41 10-25-2007, 11:20 PM

Quote:

Originally Posted by hangit

No, I'm not giving up yet. I read through some of your other help posts to members with similar problems and noticed you advised them to turn the modulator adjustment 3 turns CW. I tried a half turn tonight and it improved the 3-4 flare, 1-2 a little firmer, no harsh downshifts. I will try another full turn tomorrow.

I'll post my results.

John

Well, I was hoping to get yours to a satisfactory solution without a modulator adjustment, but.........if it works for you without a harsh downshift.........then go ahead with it.

Three turns should be fine. If it develops a harsh downshift after three turns, we can always raise the vacuum level to soften it.

hangit · #42 10-26-2007, 09:47 PM

Ok Brian, here's today's news. New cap is on the modulator and I turned it a total of 1 1/2 turns, vacuum to modulator is still at 7". Downshifts are now clunking. 3-4 flare seems a little worse than when I only turned 1/2 turn.

Where to go from here. Thanks again.

On a good note, I got both of my electric seats working and my hood prepped for a new pad!

John

Brian Carlton · #43 10-26-2007, 11:47 PM

Quote:

Originally Posted by hangit

Ok Brian, here's today's news. New cap is on the modulator and I turned it a total of 1 1/2 turns, vacuum to modulator is still at 7". Downshifts are now clunking. 3-4 flare seems a little worse than when I only turned 1/2 turn.

Where to go from here. Thanks again.

On a good note, I got both of my electric seats working and my hood prepped for a new pad!

John

Not a good sign.

If the increased modulator pressure won't cure the 3-4 flare, there are not a lot of options.

You could try some additional vacuum to reduce the clunking, but that's only going to aggravate the 3-4 flare.

That transmission is near the end..............

hangit · #44 10-27-2007, 07:52 AM

Quote:

Originally Posted by Brian Carlton

Not a good sign.

That transmission is near the end..............

Know any good transmission shops near Green Bay?

John

Brian Carlton · #45 10-27-2007, 08:30 AM

Quote:

Originally Posted by hangit

Know any good transmission shops near Green Bay?

John

Like anything else with these vehicles, most repair shops don't know squat and you'll spend a bunch of money on a poor product.

The best choice is to find a shop that will remove and reinstall the transmission for $500.

Then, get a rebuilt unit that you can trust from Sun Valley or one of the other West Coast shops that know these units well. The cost is about $1300. or so.

If you go local, they'll hit you for well over $2K and they may or may not know what they are doing.