4 Speed Gear Box

[ted280sl]

My 1969 4 Speed gear box could use some improvements. It leaks and the synchros are not as good as they used to be. My non-specialized mechanic told mehe could have someone rebuild the gear box but, repirs could cost anywhere from $300 to $3,000 and he would not know until the box was open. I was hoping that with our joint wisdom and experience someone could provide some additional insight.
Thanks,
Ted 1969 280SL (It is slow to shift but, runs great in gear)

[Mike]

I had this done last year at a cost of about $1,000 for parts and labor.  I was told that I was lucky as I only needed synchros and bearings on the countershft.  If it would have had bad gears or shaft the price would have been much higher.

Michael L. Hund

[ja17]

Hello Ted,

These transmissions usually do not wear synchros out. However they are fairly inexpensive as are the bearings, so they should be replaced as a standard practice during a rebuild. If your transmission nips, going into some gears, or grinds during quick shifts, and if your speedometer needle bounces when letting off the gas pedal, you probably have a loose slotted nut on the transmission output shaft. This nut tightens the 3rd and 4th gear cluster and keeps the speedometer sending gear tight in the cluster also. This slotted nut is nested in the output flange of the transmission and just in front of the drive shaft.

Re-tightening the nut does not always solve the problem since the gear cluster may shift and not allow a key to re-seat in the transmission.

Make a sure you have automatic transmission fluid in your gear box and watch your speedometer needle next time you de-accelerate.

If your transmission is not "out" altogehter, then you robably do not need much in the way of expensive "hard" parts.

More common finback and some W108 Mercedes sedans of the era had basically the same transmissions, except for the top covers. So economical used hard parts may be available.

Joe Alexander
Blacklick, Ohio

[Ben]

I have a spare tranny which I intend to open and rebuild in the next few months.Whats the deal with that keyway Joe, I recall seeing it when I opened my current tranny but I'm not happy with that job !

Regards,
Ben in Ireland.
'64 230SL 4sp.