Hey All:

I just bought a 1980 300 CD with 110,000 miles on it. Styling ride! Everything is working very well except it changes gears very hard.

Any ideas?

Let me know.

Thanks.

Matt

fluid level or a vac issue is my guess... i have a 240D so i dont know much about the vac controlled transmissions

Check for vacuum leaks and check VCV and tranny modulator.

Hard shift can be caused by absence of vacuum, improperly adjusted or defective modulator.

Vacuum leaks in locking system, HVAC, etc. can also cause hard shifting.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Vacuum problem. Get a Mity Vac and do some checking. In the meantime, block off the vacuum going to the door lock system and shut off the heating system (far right button on climate control pushed in) and see if your shifting improves.
OOps, you probably have the up/down climate control and the dreaded ACC servo. Push the off button.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

On a 1980 when there is a shifting problem,
check the valve on top of the engine valve cover.
The 3 way vacuum valve.

I drove for years with a hard shifting trans. Thinking I needed the K1 spring kit.
A test with a mighty-vac like device showed that this little valve leaked.

If the little arm is worn that can be purchased separately. The valve complete is
maybe $40. Fastlane (the board sponsor has them), so does the dealer.

After replacing the valve on my car the trans now shifts smooth.

It is a simple fix.

__________________
80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

I would also suggest ridding the car of the EGR valve and the 3/2 swithes on the valve cover. Both of those tend to do more harm than good when functioning improperly. They are also sources of vacuum leaks. Once that is done, hook your MityVac to the outlet side of the VCV so you can see what the vacuum is that your trans is seeing at various throttle positions. There is a very good article on this particular topic that was started by "firemediceric". Brian Carlton chimed in on that thread and gave some good solutions.

__________________
2005 Accord Hybrid (Wifes)
1995 Subaru Impreza L AWD (Snow car)
1984 GMC Sierra 1500 (Mine)
1983 300CD Best $ I ever spent. (Mine)
1984 190D (sold and glad I did)
1983 300D (sold and wished I hadn't)

Good info for sure, but it doesn't apply to your particular year model. Rhodes2010 is heading you in a good initial direction. Had an '80 wagon, so I had to deal with that 3/2 valve on valve cover, then adjust tranny modulator. The modulator adjustment (modulator on passenger side of tranny) had more to do with shifting interval, not firmness of shift. You are lacking sufficient vacuum for a smooth shift.

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John