Gear Oil for 89 Turbo with LSD

[djtalon]

What gear oil do most use for the LSD cars? I did a search and have come up with 100's of different answers which only confuses me. I though Redline MT-90 was good but not sure.

[Pete R]

I'm am using MT-90. I contacted Redline about it because I was questioning the hypoid gear application. I also was worried about the corrosiveness of gl-5 lubricants of the syncros. This was Their response:


Pete,
The GL-4 MT-90 is not suitable for use in a typical hypoid rear wheel drive differential as it does not quite provide the extreme pressure protection required.
Your transaxle doesn’t contain high offset hyoid gears which would require an EP GL-5 lubricant. A GL-4 is suitable for straight cut as well as zero and low offset hypoid ring and pinion gears typically found in a transaxle.


The MT-90 would be suitable and will perform well in your 944 turbo transaxle.


Regards, Dave
Red Line Oil

[Matt Monson]

I recommend the use of a GL5 gear oil in all Porsche transaxles. You'll find a lot of debate about LSD additives for use in cars with LSDs. Our official position on it is that an LSD additive is primarily an NVH item. It makes the LSD run more quietly in a street application with less crack and clatter. However, because the additive makes it more slick, it actually makes the lock up of the LSD less effective. If the car is raced or tracked and you want to get maximum performance out of the LSD stay away from the oils with additives in them.

With respect to Redline in particular I doubly emphasize to stay away from the variants with additives. Not only do they hinder performance of the LSD, but I have seen in a racing application on a hot Summer's day during longer endurance type races the oil gets too slick for the synchros to work properly producing balky shifting and in some instances the inability to shift into certain gears (usually 3rd, the most used gear) at all.

Kind Regards,

Matt Monson
Guard Transmission LLC

[Pete R]

Originally Posted by Matt Monson

I recommend the use of a GL5 gear oil in all Porsche transaxles. You'll find a lot of debate about LSD additives for use in cars with LSDs. Our official position on it is that an LSD additive is primarily an NVH item. It makes the LSD run more quietly in a street application with less crack and clatter. However, because the additive makes it more slick, it actually makes the lock up of the LSD less effective. If the car is raced or tracked and you want to get maximum performance out of the LSD stay away from the oils with additives in them.

With respect to Redline in particular I doubly emphasize to stay away from the variants with additives. Not only do they hinder performance of the LSD, but I have seen in a racing application on a hot Summer's day during longer endurance type races the oil gets too slick for the synchros to work properly producing balky shifting and in some instances the inability to shift into certain gears (usually 3rd, the most used gear) at all.

Kind Regards,

Matt Monson
Guard Transmission LLC

So what brand do you recomend, It's only 2.5 quarts.. I'll change if something is better

[phoenix_iii]

SWEPCO fan here... =) Heck, I think I still have enough if you are local and want to buy it cheap. =)

[mcarter]

I like Swepco 201 gear oil in my 89' 951!!

[phoenix_iii]

Originally Posted by mcarter

I like Swepco 201 gear oil in my 89' 951!!

We'll how it does this winter... but that's what I went with (90% sure).

[KEV951]

swepco all the way . or torqo, but change the torqo after every hard session.

[Wassabi]

I've been doing a bit of reading as djtalon has, trying to figure out what kind of oil would be best for the transmission (as I have the same car, a 1988 944 Turbo S). I've heard a few brands get thrown around mainly Redline and Swepco. I've been kind of leaning towards Redline as that is what the previous owner told me he used throughout the car. Are there any underlying differences between the 2 oils?

Pete R / Matt Monson Call me ignorant, but I don't know much about the hypoid gears in my 944's tranny. However with Matt's comment it leads my to believe we would be better off with 75W90 NS GL-5 Gear Oil versus MT-90 75W90 GL-4 Gear Oil? While the Swepco alternative would be the 201 or 203, as they are both GL-5. I'm having a harder time gathering info on the swepco.

mcarter, how did you land on 201 as your choice of swepco gear oil? (I only ask to get a better understanding on MT oil before making a choice)

[Pete R]

Originally Posted by Wassabi

I've been doing a bit of reading as djtalon has, trying to figure out what kind of oil would be best for the transmission (as I have the same car, a 1988 944 Turbo S). I've heard a few brands get thrown around mainly Redline and Swepco. I've been kind of leaning towards Redline as that is what the previous owner told me he used throughout the car. Are there any underlying differences between the 2 oils?

Pete R / Matt Monson Call me ignorant, but I don't know much about the hypoid gears in my 944's tranny. However with Matt's comment it leads my to believe we would be better off with 75W90 NS GL-5 Gear Oil versus MT-90 75W90 GL-4 Gear Oil? While the Swepco alternative would be the 201 or 203, as they are both GL-5. I'm having a harder time gathering info on the swepco.

mcarter, how did you land on 201 as your choice of swepco gear oil? (I only ask to get a better understanding on MT oil before making a choice)

I'm pretty much confused too. As you see in my post I contacted redline and they reccomended the MT90. The 75w90 NS I believe stands for non slip which may cause the ls to chatter. I've heard that the gl-5's have ingredients that attack the soft yellow metal (brass) syncos. It seems our problem is that we have a tranny and a diff sharing the same fluid. Whats good for one isn't necessarily good for the other so it's a compromise.

[Victor Askew]

+ 1 for the SWEPCO 201 gear oil. For info go to LNN racing website.

[Wassabi]

Pete R, thanks for noting that NS meant non slip. I've been wondering what that meant. It seems you've hit the nail on the head with the tranny & diff sharing the same fluid, and I would like to know what oil is best for satisfying both.

There seems to be 2 possibilities with Redline as they seem to have many variants of the same oils (surely there is a reason for this). There's the 75W90 NS GL-5 Gear Oil as noted earlier (or a 75W90 GL-5) and then MT90 75W90 GL-4 Gear Oil that was recommended to Pete (Pete does your 951 have a LSD?). Would the MT90 75W90 be the best Redline oil for a 944 tranny with a LSD? If you plug in a 1986 944 Turbo into their application search you get the MT90 75W90 GL-4, however if you make it a 1989 944 turbo (which would make it an S, ensuring it had a LSD) it tells you to use the 75W90 NS GL-5 Gear Oil. Honestly I just want a protective oil that is going to protect my syncros and hypoid gears, preferably Redline.

On a side note, I've also read that some lubricants are better with specific kinds of LSDs, does anyone know what kind of limited-slip diff is used in 944's?

Victor, can you elaborate on the LNN racing website, perhaps with a link.

[wild man]

After hearing so much chatter about what is the absolute best brand of gear oil to run, and specifically the racers who really heat up their oil and cause it to go thin, I feel that those folk are overlooking the obvious solution - GO THICKER! As in 75W-140, with the NS additive (& NO sulpher), regardless of the brand. Most of us don't need that high of a level of protection though. Your average store-brand oil (that DOES have an NS additive and DOESN'T have sulpher) works perfectly well. Those who experience R&P or other issues most likely failed (or the PO's failed) to freshen (change) the previous oil in a reasonable amount of time. For street use, I don't think that the NS additive is even necessary. I don't exactly what type of LS configuration these diffs use, but I can tell you that they work waaaaaaaay better than the ford LSD's, which use disc clutches. GM uses cone clutches in their LSD's, but I don't think I've ever driven one, so I can't comment on their performance.

[Pete R]

yes I have an LSD, I never looked up 1989 944, it's odd that they reccomend a different oil. It's probably like Duff, Duff dry and Duff light all the same (Simpsons). I am using the MT90. I used it on the street and on a 90 degree track day, it was great. My only concern is wear at this point. I'll buy anything better to protect it if I can, @ less than 3 quart I can afford anything. I do like Wildmans idea of going thicker.

This is redline's initial response.

Pete,


Thank you for contacting Red Line Oil, glad to hear the fluid is performing well in your 928.The MT-90 is recommended and a good choice in your 944 transaxle and suitable for use with limited slip differentials. If your limited slip is a clutch type unit, chatter shouldn’t be an issue or a concern on the race track. If chatter did occur when making a slow/tight turn on the street, a slight amount of friction modifier could be added being aware that excess will impact and degrade shiftability affecting the synchros performance.


Regards, Dave
Red Line Oil

[Ohtori]

Using Startpage (web browser) I searched 'porsche hypoid gear' and this was the top link; I was searching for information about what gear oil to use in my 944S. The manual states SAE 80 GL-4, or MIL-L-2105. I was initially thrown off by the Redline application guide Red Line Synthetic Oil because it recommended MT-90 GL-4 gear oil, except it stated 'not for use in hypoid differentials' but was thinking it also included transaxles, because our trannys use a hypoid gear. My mistake.

Two articles that come up in the same search are from Blue Sky Motorsports (it's 911 trans. related, but relevant) Transmission Lubrication and from Richard Ratwell of 'The Bus Co.'---a VW Bus website Gear Oil Selection . The Blue Sky article discusses the difference between Porsche and Borg-Warner synchros---because the Porsche ones need friction to work properly they don't favour slippery fluids (like GL-5) but the Borg-Warner ones do (like in the G50 trans. in 1987+ 911s). Which describes my symptoms on my 944S where I get a very slight grind in 1st, 2nd, and 3rd, especially when cold. But it's the gear fluids I am/was using (the old Amsoil 75W90, the new Amsoil Severe Gear 75W90 and the best of the bunch, Redline 75W90 NS---all GL-5's). They also talk about how how the hypoid gears work, how the LSD works (on 911 trans.), and how the various additives affect the above.

The VW article talks about how the GL-4 spec is the gear oil to use, and then discusses the differences between GL-4 and GL-5/MT-1, and why GL-5 is the wrong lube to use in GL-4 applications. Personally, I think the two articles help clarify why we should use the spec. that's specified in the owner's manuals as they meet a standard that another spec. may not meet, even though they claim it's a multi-spec lube.

So I'm going to change out my Amsoil 75W90 Severe Gear Oil and try the recommended RedLine MT-90 GL-4 and I'll update at a later time if I've eliminated my slight grind.

I hope that these articles provide some insight for others too. And if you're really bored, you could download the military specifications for MIL-L-2105 here: MIL-L-2105 D

[89-944NA]

I used RedLine MT-90, sorry I wasted my money on it, IMHO very poor performance, I won't and don't recommend RedLine to any of my friends.

Swepco for me!!!!

[Matt Monson]

Originally Posted by Pete R

So what brand do you recomend, It's only 2.5 quarts.. I'll change if something is better

Sorry, I never made it back to this one. I don't subsribe to many threads and if I don't sweep through the forum very often I fail to reply.

I don't actually recommend any single brand other than the comments I made above about what NOT to use. There's a lot of good gear oils out there. IMO, the number one thing is service interval. On these cars, I never like to see them go over 15k mi on the gear oil. Change it every two years regardless of mileage. If you track the car, count a weekend at the track doing DE as 2500 mi against that 15k. If you race the car, change it after every 2nd event, or every event if you want to be uber diligent.

[Wassabi]

Originally Posted by 89-944NA

I used RedLine MT-90, sorry I wasted my money on it, IMHO very poor performance, I won't and don't recommend RedLine to any of my friends.

Swepco for me!!!!

Can you elaborate on what you did not like about the MT-90? I'm currently using it and couldn't be happier. Not to say that you're wrong, but I'd like to know why you think it's not worth the dollars?

On another note, OHtori - excellent breakdown, I like to hear the specifics and not just use brand X because it's better...

[Litesonic]

Thanks all, I just picked up a new trans to install and I was going to flush the oil in there. What a great time to make a change.

[John_AZ]

another opinion...

Ian at 944online rebuilds the turbo S transmission and only uses Royal Purple....

944 Online Forum - The Porsche 944 Forum For The 944 Enthusiast.

John