I'm trying to figure out why my 350's trans shifts so firmly at part and light throttle. I've adjusted the modulator and vacuum control valve per the FSM. I've checked the vacuum amplifier. I get about 14" of mercury at idle, which makes about 20 psi of modulator pressure.

I've taken apart the VCV and cleaned it, replaced all the vacuum lines, verified no leaks in the climate control system... to me it seems like I need more vacuum at idle. If I hook up my hand pump to the VCV and pump it down to 18-20" the modulator pressure goes to nearly 0 and the light throttle shifts are perfect.

I'm wondering what the "correct" modulator pressure at idle (with the vacuum line connected) is. If anyone has checked on their trans could you post in this thread?

Here's a quick video I made: https://www.youtube.com/watch?v=gxVsT65PjjM You can see how the modulator pressure drops when a gear is selected, and at the end I use the hand pump to show the relation between vacuum and modulator pressure.

I'm thinking I might add a switch to the throttle linkage which operates a solenoid switching in more vacuum at light throttle.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

You are going to get yourself really confused if you try and adjust to what everyone else has! The data in the FSM chapter 27 is varied.

Assuming you have the original transmission => 722.361

You should have a red coloured dashpot or a brown coloured dashpot with out pressure converter; 290mm diamter torque converter and a modulating pressure of 3.3 bar (red dashpot) or 3.1 bar (brown dashpot). WARNING! This is data for Australia and Japan - can't find US regional data or national data for 722.361...



Anyway according to chapter 27 you first need to adjust the modulating pressure to the correct pressure. After this at idle - with transmission oil at operating temperature - vacuum of 385 +/- 25 mbar is the value you should have.

You then need to check the coolant switch (I can post more on this if you want)

There are two more tests after this - if you get this far I'll post up the rest of this procedure if you need it.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

You mean you tightened the internal spring in the VCV? If so, how many turns?

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Coolant switch? The 350s don't have one of those. I have the original 722.361. My dashpot is red. 3.3 bar is 47 psi... a lower number than what I saw in other references (55 psi).

Full throttle shifts are fine.

What car does it show that transmission used in? As far as I knew the 3.5 diesel was USA only at that point, unless they had used it in G class or something.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Loosen the 2 bolts holding the VCV to the injection pump, hold the throttle completely open, turn the VCV until you feel resistance, tighten the bolts.

126.135

Sorry I see you are 603.97 not =>

Engine type 603.96X description shows coolant switch - big deal about above 50 degrees C and below 50 degrees C

I don't have specific data for 603.97 engines...

...bugger you are on your own buddy! Time to find someone with access to WIS

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Heheh. The joy of owning a car with late run production changes

-J

I guess I should add... I suspect there are other problems with my transmission besides the modulator settings. I'm mostly looking to see if other's cars modulator pressure is near 0 at light throttle since anything higher than that on my car produces harsh shifts.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Well if it doesn't have the coolant switch hassle it might be easier than you think...

Or are there other gubbins are fitted?

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

There are just 3 devices... the VCV on the side of the injection pump, vacuum amplifier (which takes in the boost signal), and the modulator.

It might also be possible that my VCV is bad... simply not passing enough vacuum at low throttle.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

If I remember correctly, your vacuum is supposed to go to zero immediately when you give it the throttle and you will get a smooth upshift with zero vacuum. You need vacuum only for smooth downshifts. I think you should be between 13 and 20 vacuum at idle and zero at WOT. When you adjust the vav you may need to check the gap (cannot quite remember what to call it but between the vav and the outside rod on the right side of the vav which pulls back and forth - there is supposed to be a specific gap - has been a long time).

Anyway Kerry should know.


Kerry, are you out there?

I have a Corteco manual that I found online somewhere. It says:
Modulator Pressure
722.361
Red
PSI = 55

Pressure adjusted with no vacuum, in drive @ 31 MPH

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

No electrickery attachments? Really? That's not like modern progress!

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

The 603 motors don't have an external linkage, it bolts right to the internal linkage on the injector pump. If I could get that much of a vacuum range (20 at idle and 0 at WOT) I think I'd be happy.

-J

Did not know. My 81 300SD got a new tranny and the installers knew nothing about adjusting it. Really violent shifts. I finally got the modulator adjusted and fooled around with the vav enough to reset it. I reset the gap too. Kerry helped a lot in identifying what I needed to do.

My vac at idle is now about 14.

Guess the newer engines are improved.