I have a 91 740 I bought for my daughter's first car. We repaired the wires
from the generator to the speedometer, the odometer works but speedometer jumps
around mostly but ocassionally works properly. Any suggestions? Many thanks!

If the ABS light is not coming on, the rear axle pickup used for both is not defective and the problem is in the speedo head.

Hey I have a 1990 740 and the speedo and odometer both have gone out on me or at least jumped around. Ihave been told the is a magnetic sensor near the back wheels somehwere. That may be the problem at this point if it jumping around on you. Im not sure how much the are but I've been told they are not much and should not be that hard to replace. If any one has mor info please submit it. Again I am going of hear say from an Imports mechanic, but yeah so I'll post more when I find out

Yes, the speedo is a separate gauge in the cluster. The culprit is probably bad solder connections on the drive board of the speedo head as is common to all Volvo gauges and controllers. The reason for zeroing in there is that the only three connection required for the speedo assembly are common to the odometer too.