'88 B2600 4WD speedometer gauge

hi guys! my truck's speedo wobbles & sometimes goes/points to 100-100kph right after leaving the garage eventhough i'm just doing 10-20kph. it goes back to normal after travelling a few kilometers. what's busted? i already checked the speedo cable and it's ok. i reoiled it but speedo gauge still is 'wobbling'.

is it the drive gear [cable connected to the transmission] with part# M515-17-441?
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OR still the
speedometer cable [part# UC8660070B]
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help!


thanks,
azzkkr2600

Question for you.You said you lubed it but with what.I will suggest take the speedo cable out from cluster to trans.Then pull the inside cable out of the housing and use brake cleaner and clean.Then use some wheel bearing grease (lightly coat) it and slide the internal cable back in.The putting of grease just in the ends going to the trans and cluster does not work effectively.By cleaning the internal cable and lubing coats it to prevent irratic movement and unless after this it does the same I would lean more towards the cluster being the issue maybe.I would have chimed in sooner but,had a serious sinus infection last wk and just out of it,and feeling crappy.I suggest trying my idea remove speedo cable and remove internal cable and go that route,1st and see if this corrects it.Heat and cold kills the grease over time and makes needle jump and slow.

thanks for the tip! will update you soon!