Rookie diff/tranny fluid questions.......

[Zesty]

I am looking to change these fluids in my car soon. I think I have the procedures and capacities down, but I'm still confused on which fluids to use.

Car is a manual, and has stock VLSD. I am just looking to do the change with cheap stuff right now. Will look into more expensive stuff for next time I change.

I assume 80w-90 is good for where I live(Central Coast California). I am just kinda confused on the GL-4 and GL-5, and which is suitable for where. If anyone can give me a quick definitive answer, that would be great. Thanks.

[RightWheelDrive]

The VLSD is a sealed viscous unit so whatever fluid you put in there won't really affect its performance. just use some redline 75w-90(GL-5 iirc), $14 for two bottles and call it a day.

[upSLIDEdown]

I am looking to change these fluids in my car soon. I think I have the procedures and capacities down, but I'm still confused on which fluids to use.

Car is a manual, and has stock VLSD. I am just looking to do the change with cheap stuff right now. Will look into more expensive stuff for next time I change.

I assume 80w-90 is good for where I live(Central Coast California). I am just kinda confused on the GL-4 and GL-5, and which is suitable for where. If anyone can give me a quick definitive answer, that would be great. Thanks.

Tranny---GL4 (Our trannies use brass syncros, and GL5 corrodes/eats away at brass syncros) I suggest Redline MT-90 for the tranny.

Diff---GL5 IIRC, I'm using Mobil 1 Synthetic GL5

[dopeassjackson]

im going to throw some penzoil synchromesh in my tranny. its $6 a bottle at auto zone.

[Zesty]

Thanks everyone.

[LigouriRd]

im
going to throw some penzoil synchromesh in my tranny. its $6 a bottle at auto zone.
:werd: -That is some good sheeet for the money. Fixed my grinding going into 5th. Expect to have to go to 2 autozones at least, around me they only carry two bottles of the stuff and you will need three. :wtf:

[NemeGuero]

Redline for the win.. that's some good fluid right thurr.. Tastes like root beer.

[LigouriRd]

ahem
I am just looking to do the change with cheap stuff right now. Will look into more expensive stuff for next time I change.
Penzoil Synchromesh!

[Zesty]

OK, I went to the AutoZone in my town, since that's the only auto store we really have.

The cheapest stuff was some "Coastal" brand 80W90. It said it was only good for "topping-off" limited slip diffs, which scared me. I remember what RightWheelDrive said and so I figured since mine's a VLSD it should be cool. Is it okay to use in my VLSD, even though it says it really isn't intended for LSD's?

Also, if I remember correctly, the Coastal is GL-3, GL-4, and GL-5 rated....would this mean it is no good for my manual trannsmission? I saw the Pennzoil Synchromesh there, and you guys are right there was only 2 bottles! If this stuff is really that good, I guess I should probably go with this. But the bottles did NOT say anything about having any sort of "friction modifier", which I have heard is the one I want! It also didn't say anything about being GL-4 or 5 that I could see, just that it was approved for Chrysler and GM, and that it was NOT intended for all trannies....but it did also say it did not harm yellow metals.

So in a nutshell:
1)Is the Coastal brand 80W90 gear oil OK for my VLSD, even though it says to "use only for topping off LSD's"? I assume it's okay since I have a VLSD, but I want to make sure.
2)The Coastal says it is GL-3, GL-4, and GL-5 rated....what does this mean exactly? I assumed since it says GL-5, it is no good for my tranny. Also, I am willing to spend the money for the Pennzoil Synchromesh, so long as it is not gonna harm my tranny.....but the bottles didn't say anything about "friction modifier". Do I need to get the one with friction modifier, and is the Pennzoil Synchromesh for sure safe for my transmission?

[Zesty]

also, is the 80w90 okay for my VLSD, or do I need a thicker viscosity?

[upSLIDEdown]

Yes, the Coastal is GL5, which means it will eat the syncros in the tranny. The 80/90 should be fine in the diff though I think. Don't quote me on that though, I don't remember what the Mobil 1 I used was. The Syncromesh is supposed to be good stuff, but I've far more outstanding reviews of Redline MT-90. I would go with that, even if you have to order it. That's what I run in my winter vehicle, and as soon as I get time, that's whats going in the 240.

[Zesty]

^Thank you sir.

Also, through further research, I am almost positive that the cheap coastal stuff will be fine in my diff, even though it is not for LSD's. Since the VLSD is sealed it should be fine I figure.

[Zesty]

OK, sorry to bring this back up but I have a couple more questions please.

Through more searching I found http://www.zilvia.net/f/showthread.php?t=13330&highlight=gear+oil, which says it is fine to use GL-5 in the transmission, so long as it also has the MT-1 designation.

Yesterday I bought a gallon(4 quarts) of Valvoline 80w-90 gear oil. I bought it specifically for my diff. But it is GL-5, MT-1.......would it be okay to use 2 quarts of this in my tranny and top off with the Pennzoil Synchromesh?

[upSLIDEdown]

OK, sorry to bring this back up but I have a couple more questions please.

Through more searching I found http://www.zilvia.net/f/showthread.php?t=13330&highlight=gear+oil, which says it is fine to use GL-5 in the transmission, so long as it also has the MT-1 designation.

Yesterday I bought a gallon(4 quarts) of Valvoline 80w-90 gear oil. I bought it specifically for my diff. But it is GL-5, MT-1.......would it be okay to use 2 quarts of this in my tranny and top off with the Pennzoil Synchromesh?

No. As far as I know, it has to be GL4 for tranny. VLSDs don't care since they're sealed. It should need any LSD additive. Again, personally I would order MT-90 for the tranny. It's not THAT expensive considering most people don't change it very often. That's my final word on the subject.