Best weight of trans oil - 75W90 or 75W140 ??

[Martin S.]

I have 75W90 synthetic gear oil in my new Rancho pro street trans. It has been working fantastic and I love the way it shifts, nice and solid!
I wanted to change the oil this year and wondering about the two weights offered and if the 75W140 would be better than the 75W90 that I have in it now.
When cruising on the highway, and then suddenly slowing down by getting completely off the gas but keeping it in gear, I hear a bit of a howl from the trans as I slow down.
That noise was there as well with my previous stock 1968 transmission with this setup, but I'm surprised to hear it with the new trans. I have a couple thousand miles on it now.
Any suggestions?

Here's what I was thinking of trying:
http://www.idparts.com/liqui-moly-fully-synthetic-hypoid-gear-oil-75w-140-p-6171.html?gclid=CNjwxI7BwtMCFYE6gQodmRoPlA

[Torben Alstrup]

Although I am NOT a fan of Castaway oil,...... erhm Castrol I must admit that their 75W/140 racing transmission oil is not bad at all. On top of that with the sub quality super diffs theý install the 75W/140 will come in handy to deliver a tad better lubrication to the end gears.

T

[Martin S.]

fuck I hate slowing down.

[Andrew]

There was a thread on here discussing whine on overrun; it seems quite common on big engines cars.

My box does it, you could say it's because it's older and got miles on it, but then again some say parts were better quality back then? I dunno...neither does that answer your question. Be interested in feedback if you do change grade. Does Rancho have any advice?

Andrew

[Martin S.]

Thanks, that is interesting about the whine. I started hearing that with my new 2332 and didn't get it with the 1776 before that. I thought it was the trans going bad, but now that the noise is still there it makes me wonder. I emailed Rancho yesterday, and didn't mention the whine, but regardless I am interested in what grade they recommend. I'm also going to throw a bottle of Ceratec oil treatment in as well, as it can't hurt and is recommended for manual transmissions. https://products.liqui-moly.com/cera-tec-1.html

[Torben Alstrup]

The only way you can reduce the whine and fix the problem is to take that crappy super diff out and machine the crap out of it, so the ouil can get around in it as it is supposed to. OR install a Quaife.

There is a reason to why we have not used Rancho boxes for almost 5 years now. Stock or performance.

T

[Martin S.]

So is the answer to stay on the gas? 

[Jesse/DVK]

So is the answer to stay on the gas? 

When in doubt, flat out!

[Torben Alstrup]

So is the answer to stay on the gas? 

Hehe, yes, that is an option.
Another option is to take the box apart and do the mods THEY SHOULD HAVE DONE, BEFORE assembelling the transmission.

[Martin S.]

OK thanks! I'll keep that in mind when rebuild times comes. The sound is not normally a problem. But the car is fairly quiet being a turbo with a flat pack so is not too noisy. Rubber mounted Berg mid mount, with no rear engine brace. Rancho ignored my email about gear oil weight recommendation.

[Neil Davies]

So is the answer to stay on the gas? 

Hehe, yes, that is an option.
Another option is to take the box apart and do the mods THEY SHOULD HAVE DONE, BEFORE assembelling the transmission.

Torben, do you have a link to these modifications? I'm about to put a second hand super diff into a box for Drag Day and I wonder if the mods have been done already?

[Eddie DVK]

So is the answer to stay on the gas?  

Hehe, yes, that is an option.
Another option is to take the box apart and do the mods THEY SHOULD HAVE DONE, BEFORE assembelling the transmission.

Torben, Is there a 'how to' on those mods?

Mod: Sorry 2x

[pupjoint]

i have been using MOtul Gear 300 75-90 on my rebuilt transmission and no issues and no noise

[Martin S.]

Did you try 75W140 to compare? I was wondering what the difference is.
When I get a chance I will record the sound with my phone and post it.

[pupjoint]

no, unfortunately i did not

[Torben Alstrup]

So is the answer to stay on the gas? 

Hehe, yes, that is an option.
Another option is to take the box apart and do the mods THEY SHOULD HAVE DONE, BEFORE assembelling the transmission.

Torben, do you have a link to these modifications? I'm about to put a second hand super diff into a box for Drag Day and I wonder if the mods have been done already?

Sorry, havent been on for a while. - Actually Ray Vallero, or rather Dsimas (if I rememmber the screenname correct) made a thread over on the Samba about it not long before Ray passed away. That thread describes the modification needed to the china diffs pretty good..

T

[Dougy Dee]

Dsimas62

This thread? https://www.thesamba.com/vw/forum/viewtopic.php?t=622360&highlight=diff+mods

[Neil Davies]

So is the answer to stay on the gas? 

Hehe, yes, that is an option.
Another option is to take the box apart and do the mods THEY SHOULD HAVE DONE, BEFORE assembelling the transmission.

Torben, do you have a link to these modifications? I'm about to put a second hand super diff into a box for Drag Day and I wonder if the mods have been done already?

Sorry, havent been on for a while. - Actually Ray Vallero, or rather Dsimas (if I rememmber the screenname correct) made a thread over on the Samba about it not long before Ray passed away. That thread describes the modification needed to the china diffs pretty good..

T

Thanks Torben, and thanks Dougy for finding the thread! Just had a read through the first page - very interesting!

[PPRMicke]

Ps
We some have used Motul 90 Pa  ( sae 90 )
Those who have used is Stian / johan Dryselus / Andreas J and I
There is no metal in the oil even though it has been 800hp
/// Micke

[Martin S.]

Interesting mods for oiling. It makes sense that more oil flow will improve life, but would more oil flow make the noise disappear? Obviously the parts haven't worn out due to lack of oil since the diff is still new.
I have some Royal Purple 75W140 to try and I will check for metal when I drain the 75W90.

[Torben Alstrup]

If the thing isnt assembeled correct in the first place neither oil or the mods to the diff will make the noise go away. If you have got a new Brazil R/P it is a known secret that they will make noise for some 1500 km and then they will slowly "shut up" as they "wear in" so to speak. The oli mods to the diff is to get the proper amount of lubrication into the diff gears and end gears so the transmission wohnt start tapdancing on journeys longer than just around a few blocks. Super thin oil like the 75/140 can and will to some extend help because a little thin oil out to the end gears is better than none. So if somebody have this probklem and are not in the mood to pull the transmission, the thin oil is definitely worth a try.

T

[Martin S.]

Makes sense, thanks Torben. I was thinking that the 75/140 is thicker compared to 75/90? My under the decklid turbo engine runs super hot, often approaching 250 F oil temp when I keep up with fast moving traffic. I was thinking that much of that heat gets transferred to the transmission and a higher viscosity when hot (140) would help give some cushion against the noise. Also the Ceratec additive by Liquimoly has been tested and proven by TUV to reduce metal to metal friction so it may help to stop the galling where there is a lack of oil and make the trans last a little longer before rebuilding.
I have less than 1000km on this transmission and I'm looking forward to racking up the usage this season with it. So far it has made the car a lot more fun to drive and well worth the money.

[Torben Alstrup]

Yeah, I know some people are really into the Liqui Moly oil and additives. They havent convinced me yet. We seen it on a couple of high power vehichles (2010 Jaguar XF and and another customers Bentley turboR plus tried it in my own daily, a pumped 2,5 V6 TDI  Lets just say that we rather immediately went back to some other brands that we have had good results with over time. I never had the cahoneys to try the oil in an ACVW yet. Just an idea I have. I may be right and I may bge wrong.

The transmission oil may be a totally different game, we have seen that before.

T

[Martin S.]

I've been using the 5W40 Liquimoly Synthoil in my turbo since day one when it was first built and on the road, back in 2009. I put the Ceratec additive in last summer. So far so good, as the engine has been awesome for me every season since then with thousands of miles and driving it every day to work as my daily driver from May until November. I tried the 10W60 as well and I did see the oil pressure controlled better when the temperature spiked on the highway in hot weather. Since then I have swapped the oil cooler to an improved Setrab setup and thought the 10W60 was unnecessary and went back to the 5W40.
I don't know what to notice with different oils, and maybe you could fill me in on that? Valve adjustment has been very minimal which pleases me considering how much cam is in it.
I was going on the advice of the builder for the oil (wanting the best readily available here in Toronto) , as he was saying that since we were going with a German theme to the customized turbo motor and the car in general, the Synthoil made sense. 

[Martin S.]

I got the car out of storage on Friday and when I drove it I didn't hear the whine on deceleration as I remembered which was good. I had the Royal Purple 75W140 ready to go, so I drained the 75W90 (a generic synthetic gear oil) and glad I did because there was a sheen to the oil which looked full of fine metal particles, and as well the magnetic drain plugs were full of metal bits (see pics) [ Attachment: You are not allowed to view attachments ] . Drove the car around the block and so far I don't notice any difference but I will drive it more and see if I like how it shifts. There is a total of about 3400 kilometres since new on this transmission.

[Torben Alstrup]

I was discussing this issue with lack of oil to the end gears with an old friend the other day. He reminded me that VW themselves used sideplates with oiling holes on their swingaxle LSD gearboxes. I had totally forgotten about this. But this oil mod to the sideplates helps oil get  to the end gears especially on long straights. Maybe we should look a little into that again.
T

[Martin S.]

I wasn't aware VW made LSD gearboxes. Was that for the all wheel drive vanagon?

[Bruce]

It's not an LSD gearbox, it's a limited slip differential in a standard gearbox.

When VW installed a swing axle LSD, they used side covers that had holes in them to allow oil to go around the diff bearings. This modification is useful on very low swing axle cars.

The fuzz on your drain plug is normal.  Every gearbox with miles on them is like that.  Chunks of steel are what you need to be concerned about.

[Dougy Dee]

The grey metallic sheen in the oil may be from the MS  bearing pounding the gear carrier.

The fuzzys on your magnet may be your late model mainshaft spinning in the MS brg bore from poor lubrication. This seems  to be from low oil levels or too thick oil not getting in to the bearing. Almost every 9Tooth MS I have harvested over the past 5 years has been worn, .002 or more, where the MS brg is sweated on. One common factor is higher torque motors (ie: TDI, Subaru) conversions in buses. Higher HP T1 and T4 engines in 113 transaxles too.

The Chinese MS bearings dont help.

[Andrew]

Is it just fuzz, or are there lumps of metal on that plug? It could be the photo, hard to tell.

Andrew