English Howie

Hi gang. Well my L48 has now got new paint, so that should make it go faster. And so I'd better change the oil and filter. But not going to start another oil thread, it's getting dino 20-50 will 1200 ish ZDDP.

But what oil filter? I dunno what all these anti suck back valves and stuff mean! So any advice would be appreciated please.

I've had a couple of slight clunks from the back when I've pulled away, so I don't think there's any harm in changing the diff oil... what spec should I put in there, and any LSD additive...?

Please tell me what to do and thanks a lot in anticipation of some help and advice!

Easy Mike

Use the GM recommendations in your owner's manual.

English Howie

I know, that would be easy, Mike!
I hope this information maybe in the manual, but it's in the glove box, in the car which is 100 miles away, getting painted. Weather forecast for next week is dry, so I wanted to get this stuff sorted out asap, order things in advance, get it done, rather than be tempted to use the vehicle when it really needs an oil change etc.

The backstory is a little dull...

vaux_2

Can't help you with the oil filter but have you checked the bushing at the front of the diff with regards to the rear end clunking.

Just had to do mine as i was getting clunking from the rear end when easing on and off the throttle.

The bottom bush was fine but when i stuck my hand up to check the upper bush (which you can't see) the rubber was non-existent.

If its a manual, you can also check by having someone put it in reverse and bring the clutch up to the biting point as if you were about to move. Does the front of the diff move when you do this? Should be solid and not move. If there's any movement it will clunk when driving.

Took about 30 mins to replace on a ramp.

Cheapest and simplest fix so worth checking it first. Pic below is for a 73.

Alan 71

Hi EH,
Here's a link to a copy of the 78 Owners Manual.
Lot's of service and maintenance information within it.

https://www.gmheritagecenter.com/doc...t-Corvette.pdf

Regards,
Alan

ddawson

Don't worry about the anti drain valves because out filters are installed upside down.

They always have oil in them. I like the Wix filters. I use a high pressure version because I have my Filter bypass blocked.

As for the rear yes on the additive, and correct gear oil.

raydog9379

I just bought the GM diff lube and posi additive off Amazon w/ free 2 day shipping and got them yesterday. I bought 2 bottles of the lube and 1 posi based on some threads from here. Need to get a little sucker/baster type deal to get it out of the diff. Prob. hit up Harbor Freight as I heard they had them for fairly cheap.

Mine has been chattery feeling/sounding after driving around for >20-30 min. for a year or 2 now. Hopefully that does the trick with that issue. Know I prob. need to do the rear trailing arms/bearings soon too, but that's pretty expensive.

MelWff

the 20w50 oil is too thick, use 10w30 or 10w40 at most. Without knowing which brand filters are available in the UK makes it difficult to recommend a filter, you can always go with AC/Delco

English Howie

Thanks guys, thanks to you all for your help and advice
(...and here's a pic of our nice and tidy Vette)