Once again Im overthinking stuff. I need a sanity check. Im replacing the gear oil in my 8.2 limited slip diff.... I bought AC Delco #89021669 80w-90 GL-5 Hypoid. Says its for use in conventional type axles. Naturally not limited slip. So I bought the AC Delco LSD additive in addition. In the past, Ive always used Valvoline 80W-90 "Limited Slip" GL-5 gear oil and the additive in addition. But the limited slip oil just has the additive built in right? So is it a waste adding additive to the LSD gear oil? Is it six 0f one and half a dozen of the other? Does it really matter?
I’ve heard it’s one or the other, not both. Don’t add LSD additive to fluid with it already; it’ll be too ‘loose’. Patrick
I've never used the GL-5 already labeled as limited slip. This GL-5 is heavy duty synthetic extreme pressure lube. No mention of LSD. Got the new grape scent which is a plus!
I filled up the diff with the Delco 80W-90 hypoid with the additive today and went to a parking lot and did some figure 8's. No chatter. Did a quick oil change and filter, topped off the gear oil in the Muncie with some GL-4 and put 12 gallons of fresh fuel in her. She's ready to go. Thanks for the advice guys
That's kind of a blanket statement. Why is that? Redline specifically recommends their synthetic for clutch type posi's https://www.redlineoil.com/75w90-gl-5-gear-oil
I'M A big believer in GM gear oil and limited slip additive .I had A bad experience with Lucas gear oil one time in new diff.
THIS IS WHY.... QUOTE FROM YOUR LITTLE ad https://www.redlineoil.com/75w90-gl-5-gear-oil This product is not designed for use in most manual transmissions or transaxles in passenger vehicles, since the extreme slipperiness may cause synchronizer mesh issues that lead to shifting problems This will cause the same trouble in a CLUTCH or cone style FRICTION base posi unit...IF you have a real tight posi and want to kill some of the tightness...then yes use it. If you want the posi to be tight then DO NOT use synthetic red line we recommend the RED LINE limited slip ADDITIVE ...IF your posi unit is way too tight...It quiets the clutches and cones very well. like Pro type units with heavy preload pressures. https://zcardepot.com/redline-diffe...6heKy22fCVArVfXP98p6Z2y73x1rqVWAaAkgKEALw_wcB Jim J D RAce
Well for most people it is not a big deal nor do they understand anyway so why try... It really should destroy any parts...But in steel clutches it helps to quiet down the chatter that happens between metal parts. The reason Brian and I do not recommend is because WARRANTY of Eaton and Auburn will not stand behind synthetic fluid in the rear. That is their rule for warranty. SO if you do not care about that or the unit is over a year old out of manufacture time frame...give it a shot. JIm
You learn something new everyday. As a rule, I try and stick to whatever the manufacturer recommended. Keeps me out of trouble. Even when it comes to our old stuff.
You will get a little card inside the box of any new posi unit,with the warning about the synthetics. Maybe it would be better to say that you can run synthetics in a Tru-Trac or spool.
Gear shop that installed my Tru-Trac said either was fine in it. He's the one that will have to warranty it!
Ha Ha warranty...That is a good one. You guys that ask about warranties are funny. ALL the small print you will see how good warranties are. Just do your home work before you take it to any shop first. ASK A LOT of questions and if they do not have the time to explain what answer are...Then do not think they are going to spend 1 second of time in warrantying anything for you. Plus warranty does not include the price to install and reset up gears and anything else that get taken out. SO... be careful and do homework and recommendations. Good luck. Oh true trac does not have cones or clutches that is why you can use synthetic... same with a spool NO moving parts at all. Jim J D Race
Hey, you get a case of synthetic for free from your bud, then you have no choice but to buy the Tru-Trac.
As I always say.....IT IS your vehicle always.... We are just here to help and guide...You are free to do what you feel is correct, always.