Rebuilt Transmission grinds (with new synchros)

[Miloslav Maun]

After almost two years of restoration works I finally took my 230 SL for a trip. It was a miserable trip because of the insufficent fuel supply which (I need to sort) but my other concern is the transmission which has been rebult (new synchros for all gears, new bearings, new seals, new Castrol auto transmission fluid).
The 2nd did grind heavily before the rebuild but even now this has not been completely solved. I am not sure about the other gears (did not drive the car much before the rebuild), but now they occasionally grind too. Could it be the transmission fluid? Too thin maybe? Or is this gearbox only designed to be shifted very gently?

P.S. At least a humble picture of the car after restoration  


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[ja17]

Hello Muf,

These gear boxes can take rough treatment and shifting when put right.  The synchros are seldom bad. Loose gear clusters and improper assembly may cause grinding and gear "nipping". Has your speedometer needle been irratic? You should be using automatic transmission fluid in this manual gear box.

Don't get discouraged, sometimes you must take one step back so you can take two steps forward!
Keep plugging away at it.

Joe Alexander
Blacklick, Ohio

[Benz Dr.]

If all the gears grind maybe the clutch isn't set up right.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[ja17]

Hello Muf,

Yes, check for a simple fix first, like incorrect fluid or clutch adjustment mentioned by Dan.

Joe Alexander
Blacklick, Ohio

[erickmarciano]

almost same problem here rebuit the transmission and new clutch , new syncros . the trans grinds when only when going in 2nd at hight RPM . what can this be unsed Mobil1 synt ATF
thanks

2004 Volvo s60 T5
1971 280sl
1962 VW bug
1971 Harley FLH
1963 gs160 vespa
1962 gs160 vespa

[Miloslav Maun]

Dan and Joe: I guess the clutch is out of question, the grinding only occurs when shifting quickly and with higher rpms. I suspect the fluid, I had similar symptom with my porsche 915 tranny when I used synthetic oil. When eventually the fluid was replaced with mineral, grinding (almost) disppeard.
For the pagoda, I used some Castrol ATF fluid (not sure which type). I think I will try a different one. Any suggestions? (I am from Europe, so please suggest brands that are available here :-) )

[Miloslav Maun]

Which brand and type of oil would you recommend?

[Miloslav Maun]

Thank you, Dan, for the bad news :-(
Anyway, I try to explain the problem to my mechanic, he surely will handle it (he's the one who rebuilt the tranny).

Another symptom I discovered (I have not travelled with the car too much, so I am only discovering things now):
When I disengage the clutch pedal, sometimes a strange sound comes from the transmission. (Like if something metal fell down softly). I do not feel anything suspicious from there, though. No slipping or jerking...

[George Des]

Dan,

I've got the 5 speed ZF box as well and have noticed that it is also pretty noisy until it warms up. I'm using the synthetic auto fluid as well. This box was rebuilt by ZF about 24 years ago and has not had all that much mileage put on it since--maybe about 25,000 or so at the most. The car was down for about 10-12 years or so while being restored in between.

George Des

[Miloslav Maun]

Reportedly, the shims on the input shaft are OK. The mechanic has recommended to drive the car a bit now, so that the new synchros "sit down" - they might be too sharp.

I guess I will drive the car now and we shall see in near future :-)

[Cees Klumper]

Hello Muf - beautiful car! However after some time looking at the photograph, I noticed that the Mercedes enamel emblem on the nose of the hood appears to be missing?

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[Naj ✝︎]

quote:I noticed that the Mercedes enamel emblem on the nose of the hood appears to be missing?

Yes, I could not work out why it looked a bit 'naked'  :oops:

naj

68 280SL

[Miloslav Maun]

Well, I was a bit hesitant to drill the two holes in the freshly painted hood. So I decided it would be better to snap off the bolts on the emblem and rather glue it in place with silicone. The car is still "under construction", so that was not a final foto :-)

[drewsalisbury]

Muf - your car looks terrific, you have done an outstnding job with it!  I suspect your mechanic made his recommendation based on years of old school experience with these gearboxes

Drew Salisbury
1971 280sl auto