1980 240D non turbo 4 cylinder manual diesel.

I can't figure out what is going on and how to check it. Whenever I shift into 4th gear it makes a quick short grinding noise. It used to make the same noise when shifting into 3rd gear, but somehow it suddenly stopped after I fixed the vacuum leaks in the car. There was a leak in the door lock system so I bypassed it. Now the grinding happens only when shifting into 4th gear.

Can someone please explain what is going on here?

Mine did it into 2nd gear. I replaced the fluid with 10w30 motor oil per my owners manual,.and it pretty much went away.

Others swear by MTF

I think the problem is worn synchro gears

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

Yeah, sounds like worn synchros. Check the oil level in the trans. How many miles on it?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

I have gear oil in mine and it shifts like butter.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Gear oil is way thicker than what a lot of people have in theirs. I'm not sure if it's lubricating properly.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Does double pumping relieve the issue?

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

It might be worthwhile to jack up one side at the rear. Have someone push the clutch pedal down. See how easy you can rotate the rear tire with the transmission in gear and out of gear. Just to eliminate the chance of a clutch that is not totally releasing.

I would drain and refill the transmission with new fluid. Assume you have already checked the current fluid level? You also might want to inspect the linkages for wear of some form of binding it almost sounds with the switch from third to fourth grinding that may easily be the cause.

Most start of grinding issues are in the lower gears in my experience on these transmissions.Not third and fourth. The problem moving as it has also indicates the syncro rings are probably okay. Also take a minute to check that the bellhousing bolts are not loose. Under engine torque loading that just might cause issues in the higher gears. The clutch could not let go totally perhaps..

Mine will grind into 2nd gear. It seems to get better, even go away, once things are nice and warmed up. I can get it to shift smoothly if I shift at the max shift points, or keep rpm's up while letting out the clutch. I plan on getting new/heavier oil in there as a first step...

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)

I had MTF in my 240's manual trans, and I started getting grinding when down shifting. I drained it and put ATF in and it shifts like butter now, and has been for well over a year.

I'd drain your trans fluid put in ATF.

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I just recently purchased an 81 240, it didn't grind when I purchased but I drained the transmission anyway and put in Red Line Synthetic D4 ATF.

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85 300D Turbo!

I double pumped all day yesterday and it relieves the issue. Not the funnest way to drive though...what does this mean?

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)

double pump the pedal or double clutch?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

You did check the fluid in the aft half of the brake master cylinder reservoir?

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

adjust the free travel in the clutch, your not releaseing the clutch all the way. and it is a good idea to check your fluid level. in trans, if that doesn't fix it then it could be a sinco.

clutch pedal, 2x.

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)