19875speed

iTrader: (2)

Have 3:45 borg warner gears, what is the best gear oil to put in? Had the fluid checked it looked like some metal flakes in the oil, someone suggested Royal Purple but I don't know what weight oil to use and if there is something better let me know thanks!

sofakingdom

iTrader: (1)

I usually use Mobil1 75W-90. RP is fine too. Use that same weight in RP.

19875speed

iTrader: (2)

ok thanks! and do I need to get a gasket for the cover?

sofakingdom

iTrader: (1)

I prefer the tubular style of gasket. IMO paper doesn't add much toward the goal.

Pro Built Automatics

The best rear end oil is Lubrication Engineers. Make sure you use the GM Posi additive. And as many magnets as possible.

Tibo

iTrader: (15)

Amsoil put out a white paper they put together on testing different brands of gear lube. It's worth a read, http://wpc.1c96.edgecastcdn.net/001C...ile/index.html

Amsoil didn't always come out on top though they did win. Mobil 1 was next. Royal purple and Lucas were at the bottom. The other big name brands were scattered in the middle.

19875speed

iTrader: (2)

what is the difference between using 75w-90 compared to the other weights?

Tibo

iTrader: (15)

If you lived in a colder climate or only did routine daily driving a name brand 75-90 should be acceptable. If you participate in motor sports or live in warmer climates a thicker 140 is fine. A synthetic should flow better at nominal temperatures before the car is warmed up also. Before you go using the more expensive name brand lubes make sure that the posi still functions. IMO no sense in putting in good lube in a differential that needs rebuilt.

LiquidBlue

what is a tubular gasket? Do they have them pre-made or are you making them yourself?

LiquidBlue

Just changed mine with a paper gasket, and used bearing grease on both side of gasket. not sure why I did that, felt like it might help seal better.

sofakingdom

iTrader: (1)

Tubular style gasket:



Comes in a tube.

They even make a flavor of it nowadays for gear oil applications.

LiquidBlue

LOL - I should have known, knowing your sense of humor.

Tibo

iTrader: (15)

RTV when applied correctly and installed correctly is much better than a paper gasket.
When you install a paper gasket you are only supposed to use gasket sealant on it. The sealant greatly helps in holding the gasket during installation an helps create a better deal. Paper gaskets still should only be used when both surfaces are pretty flat and void of any gaps. So paper gaskets are not good for stamped Steel pieces. Paper also doesn't last as long. Sooner or later it absorbs oil or fluids and degrades and allows leaks.
If you want to install the gasket dry you can use a dab or two of rtv but RTV is not supposed to be used in place of gasket sealant.

LiquidBlue

That is all good sound logic. The only thing I'd add to it is it was 30K and 25 years since last oil change (which is probably too long) and it wasn't leaking, Paper gasket only. Its a pretty cheap, maintenance item, why not do it on a regular basis. Seems to me that something that requires lubrication should be changed on a regular basis, before gasket starts breaking down. The other thing is, I really don't like removing RTV because I'm meticulous about it and ALL of it must be gone before proceeding. Which makes it all the more a difficult task, and really makes me not want to use it except for what should be permanent seals. That is probably what drove me to try the grease, hoping the gasket will fall right off during next lube change. Which I promise to do more regularly going forward

Pro Built Automatics

Amsoil is one of the better oils for the rear end. I knew Royal Purple did not do well. The reason I recommended the Lubrication Engineers is from the rear end builders I have known (besides myself) in the past and some independent testing years ago on rear end oils. Lubrication Engineers was number one and Amsoil was number two. Both are excellent oils.

NoEmissions84TA

iTrader: (1)

You need this with synthetic gear oils. The friction modifiers break down regular RTV.

sofakingdom

iTrader: (1)

It is pointless for most of us to get all wrapped up in what gear oil (or ANY kind of oil, for that matter) is "the best".

One of the most important things to remember about oil is, ANY oil that's NEW CLEAN AND FRESH is better than ANY oil that's full of metal chips and dirt.

Also, oil that you can ACTUALLY BUY AND PUT IN, is better than ANY oil that might have better "reviews" or "test results" that you CAN'T buy, or that you have to wait a real long time for, or whatever.

Which is why Mobil1 is "better" for most of us than many other gear oils even if whatever some "test" said is "the best"... it's at least "pretty good", and you can walk into basically ANY parts store and BUY IT.

The particular tubular gasket variant that NoEmissions posted up is the kind I was thinking of. Not that I've ever had trouble with the other; but if there's a kind that addresses a potential problem, might as well take advantage. Even though the substances that are used as friction modifiers have been around longer than CARS, let alone RTV, and it hasn't ever really been "a problem"; nonetheless, if something better than "what we've always used" is available, might as well step up to it.

The rears in our cars will not benefit from the oil weights that are more like candle wax. Use 75W-90 Mobil1 and be done with it. AFAIK the 9-bolt doesn't need friction modifier because the clutches (cones) are cast-iron, not composition; and friction modifier doesn't really modify the friction of metal on metal. Probably wouldn't hurt, except to the extent that it displaces lubricant, as a fraction of the total content; but probably not really "necessary" either.

thtanner

iTrader: (1)

For 9 bolts I'd never use anything but...

Torco 85w140 RGO Mineral Based Gear Oil (2 required), 1 Bottle of Torco F Type Friction Modifier (Recommended for Cone Type LSD Units).

Mine is still burning rubber at 160k and making zero noises or doing anything odd.

https://www.thirdgen.org/forums/faq-...now-about.html

scooter

iTrader: (11)

The factory Helm manual says you only add the friction modifier if the diff makes noise, chattering I think it was.

NoEmissions84TA

iTrader: (1)

From first hand experience - on my 1995 GMC truck, synthetic gear oil used - I could not keep the rear end cover gasket from getting sucked in at the sides (inline with the axle tubes) and then leaking. The vent is fine. I tried a dry gasket, gluing the gasket to the cover with RTV, RTV only, the Tuff cork gasket with the metal sandwiched in between both with and without RTV, replacing the cover bolts with studs, and even a new cover. Nothing ever worked, until I found the RTV made especially for synthetic gear oils. Now I finally have no leaks.

Pro Built Automatics

When I build rear ends (which is not too often), I will put in the best, not just what is available at the local auto parts store. A day or two of waiting, is not going to make that big of a difference.

19875speed

iTrader: (2)

So I had the fluid changed, seems to be running smooth but it keeps leaking fluid from the plug. Is there an easy fix for this or do I need a new cover?

Tibo

iTrader: (15)

I'm assuming you are referring to the plastic plug at the top of the cover? Remove the cover and clean it very well with acetone. Take it to a welder and have them weld on something like a 1/2" NPT pipe fitting or bigger. I did that long ago and it worked out great.