Limited Slip Differential

[bigjae1976]

Originally Posted by rymerc

I just changed my rear diff fluid to Redline 75w140 (with no added FM) and it seems alright. Definitely locks up (eventually) and doesn't chatter at all. Now this thread has me worried about accelerated clutch wear

Redline 75w-90/140 has FM in it.

Redline 75w-90NS/140NS has no FM in it. NS is short for no slip.

If it doesn't have NS after the viscosity...you're good to go.

[///Mobbin]

This thread has me wanting to upgrade my LSD again!

Mvez any updates?

[Mvez]

Been sidetracked with the GT3, so haven't got back around to it yet. Still on the list though!

[ban25]

One thing to note is that OS Giken can tune the LSD to your specifications straight from the factory. Just give them a call!

[Mvez]

Originally Posted by ban25

One thing to note is that OS Giken can tune the LSD to your specifications straight from the factory. Just give them a call!

True dat. That said, I've used the "factory" Giken setting on both my miata and Cayman and have no complaints.

[m3peat]

I’m hearing a low speed groaning on tight left and right turns. I had the diff fluid changed about 4-5k miles ago with the fm boosted OEM stuff. I thought maybe the non fm was put in but according to my receipt it has fm.
Other thought was it could be wheel bearings but Both sides at the same time seems a stretch and the car was just a daily driver for 8-9 years, no track/Autox. Do bearings go bad with normal driving? Other ideas?
The car has 97k miles.

EDIT: now that I think about it, I would hear the wheel bearings at all speeds, not just low speeds. Back to diff I guess.

[driftflo]

if the fm does not improve things the lsd core is shot! you will need to replace it to really solve this problem! or live with it... it will not damage anything else and will not completely fall apart anytime soon.

[ban25]

Could be wheel bearings. I did all four on my old track car. It’s a safety issue, so worth a look.

[///Mobbin]

I've decided I want to move ahead with upgrading my LSD to a track focused clutch type unit and have reached out to driftflo for his recommendation. I am still a few months out on the purchase and installation but thought I would share the process.

One thing I wanted to ask folks is how comfortable would you be installing a differential core yourself? I've done a number of installs in the past including brakes, suspension, and rod bearings, so I'm not a stranger to car work but there seems to be a good amount of nuance to getting a diff install right.

Below is an example video I found on YouTube that takes you through some of the process. I am still researching shimming, backlash, and ring-gear/pinion contact adjustment so any good resources or how-to's there would be helpful.

[inTgr8r]

Definitely interested in the feedback you get from driftflo.

Like you I do a LOT of my own work.
......I'll be doing my own rod bearings this spring.

However, Setting up a dif properly is not something I would be comfortable with.

I had to stop watching that vid.....
There are sooooo many things that are wrong with his methods it isn't funny.
.....starting with working on the garage floor

[driftflo]

Originally Posted by inTgr8r

I had to stop watching that vid.....
There are sooooo many things that are wrong with his methods it isn't funny.
.....starting with working on the garage floor

me too!
this guy has no idea what he is doing there...


installing a lsd (or even worse, a new gearset or pinion bearings) is no easy DIY!
besides a lot of knowledge and experience you also need a number of special tools AND some sets of shims (and/or a surface grinding machine) to adjust bearing preload and backlash.

here are picture documentations of some lsd insallations i did (in german language... but the pics may help anyway):
http://www.limitedslip.de/service/einbau.html (click on the accoring picture to see the full installation of this unit)

these are no step by step tutorials but you may get a little insight of how it is done. i did over 1.000 installations during the last 7 years and i had a lot of diffs here to fix the issues caused by diy-installers or workshops that also underestimated the task.

i always suggest to have the work done at a shop that does a lot of the type of axles that you want to have modified. if someone has the knowledge and tools to set nissan diffs he will fail in setting a lsd rear axle as tools and shims to set the bmw axle will be missing.

and when buying a lsd or differential parts ask the dealer if he will provide the necessary information like bolt torque values, backlash, friction torques...
if not, don't buy it there... he will not be able to help and guide you during installation and afterwards.

@mobbin: got your email and try to answer as soon as i find time. at least i already read the whole email from top to bottom ;-)

[///Mobbin]

Thought I would share a few pieces of information regarding the OE GKN Visco Lok differentials that came in our cars.

GKN Visco Lok Tech Sheet, LINK.

Apparently 2008-2010 Dodge Vipers also used a GKN Visco Lok differential and this link has some interesting information regarding the recommended fluid for the Viper version, LINK. You guessed it, Castrol Syntrax Limited Slip 75W-140, pre-configured with the right amount of fm additive for a GKN Visco Lok diff!

I emailed GKN Driveline to see if they would recommend this same fluid for our cars but haven't heard anything back yet.

Since I plan to visit COTA a few more times before I trade out my diff, I may as well try the Castrol Syntrax fluid out first (my car currently has the BMW SAF-XJ fluid with FM Booster). Will report back.

And thanks driftflo for recommending this stuff in the first place.

[///Mobbin]

Purchased from ECS Tuning and apparently this stock came from a Mercedes dealership in Germany. Going in next week.

[Rassilon]

Dis you notice any change after running this fluid vs OEM's fm variant?

[Scharbag]

Originally Posted by bigjae1976

No. A clutch type diff is going to be more of a handful than the OE LSD. You need excellent throttle control because the car is going to do exactly what you tell it.

The OE unit is softer (road manners) so you can chop the throttle and do all sorts of whatever and the car won't spin.

I would compare it to R-comps to street tires. There is a small reward for the novice but a much more significant reward for skill.

I am just getting used to my E39 M5 carrier. I can say that it is much more communicative than the GKN unit. I found the stock LSD very slow to lock. I also really like the lockup on braking. You do have to pay a bit more attention but the car does exactly what you tell it to do.

Perhaps some day I will adjust the carrier to have a 4 clutch setup with 50/65 ramps. In no rush. Regardless, it is a fun journey.

Cheers,