My 74 delta has 34k original miles on it and I am wondering folks opinions on changing the read end and trans fluid. The trans operates smooth and the fluid looks good and does not smell burnt. I would prefer to not change the tranny fluid.. The rear end fluid was up to the plug when I checked it and seemed ok, but was a very dark blackish color.

I have the factory posi and that works great with no clunking etc while turning etc. I do have a slight hum when under light load that goes away when I let off the throttle. I figured new fluid could perhaps silence this a bit.

So should I leave well enough alone, or change the fluids? The car was originally used in 74 to tow an airstream trailer.

Thanks for any potential suggestions

 

Changing the transmission fluid is not difficult, but it can be messy if you're not careful. I did it on both my '67 Delta and my '73 Custom Cruiser. If it's never been done on your car, and with only 34,000 miles on it, the fluid likely never has been changed, it wouldn't hurt to do so.

Is there any particular reason why you'd prefer not to change the transmission fluid?

I've changed the differential fluid on a car once in my life, a '64 Jetstar 88 for which I had to remove the left rear axle to replace a bearing. Again, it was not difficult, but again messy. Remove the back plate bolts, and the oil comes out. Put the plate back on with a new gasket and pump new oil in through the hole.

You say there is a slight hum, but do you know where it's coming from? If it's the transmission, change that fluid, although I've never heard a transmission hum. If it's coming from the rear of the car, change the differential fluid, although the problem possibly might not be the fluid but rather worn gears?

 

Dexron 6 in both my Olds powered vehicles, supposedly backwards compatible and superior, only semi-synthetic . Usually I would say synthetic gear usually but some supposedly have had issues with clutch posi's. Extra friction modifier wouldn't hurt, even if the new stuff supposedly has it.

 

Thanks guys. I have not problem changing either the trans or the rear end, just wanted to get some opinions. I've never owned this old of a vehicle before, but have done trans and diff/transfer case fluid changes on a few jeeps I've owned over the years.

I am assuming the hum I am hearing is slightly worn gears. It is not that loud since my wife did not even realize it.