erratic oil pressure gauge when in gear...

[txchainsawgogi]

when in park or neutral it's fine. the needle points to one spot on the gauge and stays there. when i put the truck in gear it has a few mm of travel, and when it does travel you can feel the truck shake a little. again, when NOT in gear it idles fine and does not shake. its always done this as long as i've owned it.

what would be a likely cause? in gear it idles around 550rpm and my manual says thats about right.

78 350 auto th350, no smog gear.

[beastie_3]

well when your truck is in gear, RPMs drop. lower RPMs, lower oil pressure. Maybe your pump is going out or you have restrictions in your oil galleys starving moving parts of oil, hence the shaking.

[txchainsawgogi]

thats what i was thinking, i know oil pumps are pretty cheap but i've never replaced one...

how difficult is the process?

[beastie_3]

The part that is a PITA is removing the oil pan and making sure it seals back up. I think you should remove the distributor too. See what others say about your PSI too

[Grim 82]

Specifically, what pressures does it read?

[txchainsawgogi]

i just went outside and took a video.

http://www.youtube.com/watch?v=HOWcph24WcI

you can see how the needle has a lot of wiggle to it, and everytime it moves the cab shakes a little.

[Grim 82]

Well, if the gauge is reading correctly the pressure level seems fine as far as you are not running dangerously low or anything like that. Beastie summed up the rpm to psi ratio that you see when putting it in gear. As far as the needle shaking, it could be just that the needle shakes because the cab or the whole truck is shaking.

[txchainsawgogi]

hmm.. i noticed though that the needle shake coincides with the rpm's "blipping" a little. i wonder which is causing the shake, a slight misfire? a bad oil pump?


ugh!

[jason d o]

Mine does the same thing. Ive noticed i can turn my distributor shaft the opposite way and the shaft will come up with the distributor gear. I wonder if its a worn dist. gear or a worn cam gear?

[txchainsawgogi]

I've got a new dist so I don't think its that.

[former520]

Mine does that as well at idle when worm, but even wilder.  I would swap out the sender first, they are easier and cheaper and are not above failing.  Or even test it with another gauge and see if it does the same.

[jason d o]

I changed my sender out years ago to try to see if it was it but it still does it. I also changed my distributor out for a new one but still does it. Its erratic at idle and up on the rpms.

[txchainsawgogi]

Mines the same! Worse at idle when hot. If I set the idle above the spec its less noticeable.