modulator pressure adjustment - PeachParts Mercedes-Benz Forum

pselaphid · #1 01-03-2009, 05:46 PM

I just hooked up a pressure gauge to the test port of my 722-315 transmission to test internal pressure as described in Dieseldan44's previous thread: W123 Modulator Adjustment DIY - measure it the 'right' way

I was surprised when I looked at the gauge and it said zero (0). I had no reason to suspect the gauge because I tried it yesterday using an old oil pressure gauge I had around, and it said 0 too. So, I got a new pressure gauge at the hardware store. I took almost a full turn to even get it to register then several more to get it up close to the prescribed 42 psi (2.9 bar). I had to sort of estimate it because the needle was bouncy. I must confess I was a little nervous about how much I had to turn it to get the pressure up, and had that "am I screwing up really badly?" question in the back of my mind.

Anyway, I test drove it and the previously flaring shift points are now almost undetectably instant, neither hard nor soft, just perfect. I couldn't get it to flare under the conditions it was previously. I am pleased with the result, but have nagging questions.

Is the initial 0 reading a result of normal wear, or more likely a previous attempt to soften a hard shift and going overboard? This would likely have been a dealer because I think the old lady PO only went to the original dealer. She might indeed have not liked the hard shifts.

How many of you who have tested pressure on these have gotten extremely low or 0 initial readings? And is this really just a simple matter of cranking up the pressure to what it should be and enjoying the results? Seems too good to be true and I'm trying to decide whether to worry about it or not.

Thanks.

pselaphid · #2 01-03-2009, 06:03 PM

Argh, I think I just discovered something I did wrong. Forgot to plug the vacuum line to the tranny before doing the measurement. Looks like I should redo the reading.