erratic speedo and errors of the trip master

[yves]

 I had a good ride of 200 miles with other friends in their classics and at the end of the day they have 350 km on their odometer and i have only 266 km...!
during the day the speedo needle was very erratic between 50 km/h and 100 km/h at a "constant" speed but depending if i was pushing on  the throttle pedal or not .
Reading the manual i think i have the speedo drive gear loose.... ( the speedo cable is a new one)
Before going under the car in my pit  i'd be glad to have a validation here...

[ja17]

Yes, the slotted nut in the output flange of your transmission is most likely loose. You will have to dis-connect the driveshaft at the transmission and remove the flex disc to check it. Are you having any shifting issues yet?

[yves]

not completely but  , the shaft is however  quite "fuzzy", if i go that way , have i something else to replace? while i am in that "place" ?

[yves]

Before starting the speedo cable slotted nut tightening ( arrow 1) i wonder if i can  take off all the bolts   ( arrow 3 ) and the  N°2  holding the rear of the box  without any damage ? ( i'll support the gear box before )

[ja17]

Supporting the gear box is best for disconnecting and/or installing the flex coupling.  Also remove the speedometer cable cinch nut completely to remove the speedometer cable. CAUTION, resist prying the cinch slot with a screwdriver or similar, it is easy to break off.

[yves]

Hi JA thank's for your advice. BTW what is the relation between shafting issues ( i have now more difficulties with the gear box, 2 to 3 and 3 to 2  becomes a littyle hard) and erratic speedo cable ?

[Pawel66]

Then there is the question about what is the proper torque that this slotted nut should be tightened with to ensure smooth work of the speedo. The torque, from what I remember from my previous search, may be different in manual and in automatic transmission.

Do we know what are these torques?

[Benz Dr.]

Remove the speedometer cable and insert a flat blade screwdriver in place of the cable end. Turn the driveshaft while holding the screwdriver and see if the screwdriver turns or not. If it doesn't turn the nut is loose. A simple and quick way to diagnose this problem. 

[yves]

Thank's Dan i'll do the test