The Unofficial "Ask a Stupid Question" Thread

I use whatever the owner's manual says to use as that was the standard when the car was built. Especially for pre-E10 cars.

See also: 5W-30 vs 5W-20.
 
I filled the diff with 75w250 back in 2019 and have had no problems, they aren't picky. The limited slip chatters sometimes on tight turns so it could probably use some friction additive.

Red Line Heavy ShockProof® Oil - 58204 - raceparts.com

Buy all your Red Line Heavy ShockProof® Synthetic Gear Oil from us at Raceparts USA, highly rated LSD oil, available with UPS delivery.
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It's probably due for a change, so going to switch back to Mobil 1 75w140 since it has the friction additive in it.

For an open diff use whatever's on sale.
 
I use 75w90. Like said it’s not picky, I used to use 75w140 but it’s just not necessary. With an open diff it can last virtually the life of the car without changing. LSDs with friction modifier and worn off clutch particles it’s best to replace periodically(still like 50,000 miles or more really)

Kenz said:
I filled the diff with 75w250 back in 2019 and have had no problems, they aren't picky. The limited slip chatters sometimes on tight turns so it could probably use some friction additive.

Red Line Heavy ShockProof® Oil - 58204 - raceparts.com

Buy all your Red Line Heavy ShockProof® Synthetic Gear Oil from us at Raceparts USA, highly rated LSD oil, available with UPS delivery.
www.race-parts.com

It's probably due for a change, so going to switch back to Mobil 1 75w140 since it has the friction additive in it.

For an open diff use whatever's on sale.
Click to expand...

I don’t like diff oils that have a premix of friction modifier, the ratios are always off(and usually too much). Last time I put in the cheapest parts store brand of plain 75w90 and HALF bottle of motorcraft friction modifier. Strong lockup and no real chatter
 
At 234,000 I have yet to change the fluid in the Mark... :zwall:

I think I used Valvoline 75W90 with friction modifier when I put the TL 3.73 pumpkin in the T-bird. It's been fine so far but I guess it'll be time to replace it soon.
 
I need to yank the diff on Lazarus, and rebuild it. At 550k miles, I've never changed the oil. Or had problems. It left two black marks, the last time I drove it, rod knock and all.:)
I'm still amazed that it didn't break until I put it back in its parking place.
 
I'm working on my teksid shortblock for Lazarus. The pistons I have are mark -3cc pistons, bore is stock.
I'm looking at using my npi heads, with pi cams. CR will be ~10.5:1. Am I making an untuneable mess, or will I be ok on 93 octane?
 
Grog6 said:
I'm working on my teksid shortblock for Lazarus. The pistons I have are mark -3cc pistons, bore is stock.
I'm looking at using my npi heads, with pi cams. CR will be ~10.5:1. Am I making an untuneable mess, or will I be ok on 93 octane?
Click to expand...
All good until 11:1 or higher... You probably could get away with 11.5:1 if tuned conservatively. Especially on a port injected design. That's how my 347 was designed. 10.5:1 is kind of the target for most N/A engine builders.
 
I have looked at both the tbird and cougar panels, and both would require being cut open, and then welded back together. I believe they are abs plastic, and it's available as a solvent paste, like pvc for plumbing. Leds are the easy part: cheap on amazon, as are pc boards of that size. Flashing and sequencing are easy. If you want that.

A router table and jig would let you cut the back out, then you glue your board to the cutout, and glue it back together.
3m makes an optically clear epoxy; I have some for gluing scintillators to pmt's.
 
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XR7-4.6 said:
I don’t like diff oils that have a premix of friction modifier, the ratios are always off(and usually too much). Last time I put in the cheapest parts store brand of plain 75w90 and HALF bottle of motorcraft friction modifier. Strong lockup and no real chatter
Click to expand...

When I put in the Cobra differential, I filled it with Mobil 1 and a bottle of Ford friction modifier. That was a mistake! It was pretty much an open diff at that point.
I'm at the opposite now with the Redline and no additive. It's grabbing too hard.

I ordered Valvoline 75w-140 last night. I will give it a few days of driving to make sure it is worked into the clutches. I'll post how it worked out in the "what did you do to your thunderbird" thread.
 
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