Welcome! Log In Create A New Profile

1st impressions - 17 yr old OEM tranny Fluid vs Liqui Moly 75w90 Synthetic GL5 gear oil

Tire Rack: Your performance experts for tires and wheels
Buying through this link, gets PB a donation.

Expect the best, and accept no substitute.
I decided to change the gear oil on my 2001 Box S that has almost 140,000km on the odometer. I bought the vehicle used from Rizza Porsche in Chicago back in June 2009. It had just under 70,000km when I purchased it.

Anyways, never completely happy with the shifting in the Boxster S. I tried the Pedro Enthusiast mount shortly after I purchased the vehicle, and it's still in there all these years later. There would be odd random times, where the car would not go into 3rd from 2nd under moderate to hard acceleration, of course, it wasn't something I could duplicate, just annoying.

As far as I know, it's just the factory fill that is in my Boxster. I researched the different options, and availabilities to me locally, and my indy could get Fuchs Titan Sintopoid, Motul Gear 300, and the Liqui Moly, all in 75w90.

The change over went fairly smoothly, the drain and fill plugs were very tight, requiring a breaker bar to remove. Remember Lefty Loosy, righty tighty, especially working overhead. Lots of pics online on the fill and drain plug locations. I snugged them up to factory spec about 25-30 Nm, and re installed the bracing.

I have a maxjax lift at home, so it was a fairly easy project. I could not find a fluid transfer pump that I trusted at home, so I routed a 5' piece of clear 1/2" tubing from the fill location above part of the exhaust and up above the driver rear wheel. I taped it loosely in place so that the end of the house would not fall out of the fill hole and squeezed the warmed fluid into tubing. Gravity took over the rest. Took under 2 minutes per L to fill.

---
It's warm now (high 60's low 70's last evening), but the car shifts like a Honda Accord, which to me is a good thing. I'm going to put it through it's paces on Friday as I am attending a track day put on by a Porsche dealership about 1hr away. I think the shifting action is better than with the up to 17 yr old fluid that was in the car before.

My boxster was never the best shifting vehicle in my limited stable... During the past 9 yrs of ownership, we've also had a 2002 Jetta 1.8T 5 spd (sold), 2003 Honda CR-v (5 speed), 2006 Jetta TDI (5 spd), and Honda VFR800 (6 spd motorcycle). With the fluid change, it seems it has moved from last to 1st.... will keep an eye on it.
the tranny fluid likely it was the flush/bleed that made the real difference.

Even with relatively fresh transmission fluid -- I had my Boxster transmission/diff fluid changed on schedule or sooner -- old brake/clutch hydraulic fluid can really affect and not in a good way how not only the clutch operates but how the transmission shifts (due to the clutch's operation being affected by the bad/old fluid).
No, I'm still thinking it's the new tranny fluid leading to improvement in shift feel...

The clutch being hydraulic, shouldn't be affected much by whether the fluid is new or not,,, it's still not compressible at the temperatures/pressures it sees. I did not bleed the clutch.

(I have changed brake fluid before with no difference in shift or transmission feel)



Edited 1 time(s). Last edit at 05/24/2018 09:16AM by Petee_C. (view changes)
Quote
Petee_C
No, I'm still thinking it's the new tranny fluid leading to improvement in shift feel...

The clutch being hydraulic, shouldn't be affected much by whether the fluid is new or not,,, it's still not compressible at the temperatures/pressures it sees. I did not bleed the clutch.

(I have changed brake fluid before with no difference in shift or transmission feel)

While I adhered -- almost -- to the 2 year brake/clutch fluid flush/bleed I did so because I like to try to follow the auto maker's guidelines regarding servicing. I suspected the 2 year flush/bleed guideline might be a bit of overkill but as services go it was not a burden.

At some point I lost track of time and let the fluid go around 2.5 years, but I was initially unaware of this. Symptoms appeared: It was impossible to launch the car from a dead stop smoothly. No matter how focused I was this just didn't happen. Shifting which heretofore had been buttery smooth turned into a crunch fest. Thinking the problem was (finally) the clutch or even the clutch and transmission -- I don't recall the mileage but it was huge near if not over 300K miles -- I took the car in. The SM listened as I described the behavior then asked me when I had last had the brake/clutch fluid flushed/bled? I didn't recall but assumed it had been in the last 2 years. SM looked it up and found it was around 2.5 years back. Because the transmission fluid was reasonably fresh he advised a brake/clutch fluid flush/bleed. I agreed. I mean it was this or have the clutch replaced.

Afterward the flush/bleed the transformation was frankly remarkable. The clutch was once again smooth and the transmission shifting regained its buttery smoothness.

Have to admit I noted no change in braking behavior. But I didn't really demand that much of the brakes.

So my experience made me a believer in regular and 2 years is what Porsche calls for brake and clutch fluid flush/bleed services. If the clutch or transmission seemingly "suddenly" develops issues of the real but mild sort (like I spelled out above) my advice would be to do the fluid flush/bleed. Sure, if the transmission fluid is due or close to being due to be changed have this done too. For my Boxster (and Turbo) having the transmission fluid changed was the least expensive fluid service. Boxser labor was 0.3 hour and the fluid was sometimes discounted (once to $5/liter when the service department had some left over from some warranty work).
Interesting. Thanks
grant - 4 weeks ago
I hoped the high pickup of the clutch in my track car was just air. Sadly, a simple (admittedly, underline simple) bleed the other night did nothing. I may have worn it a bit with some very aggressive shifting - a side effect of having a slow car.

I'll try again, but without a lift its just an awful job (clutch, nto brakes)

G

Grant gee-lenahan-at-vee-eff-email-dot-net
Quote
grant
I hoped the high pickup of the clutch in my track car was just air. Sadly, a simple (admittedly, underline simple) bleed the other night did nothing. I may have worn it a bit with some very aggressive shifting - a side effect of having a slow car.

I'll try again, but without a lift its just an awful job (clutch, nto brakes)

G

Don't recall the pickup/engagement point changing after the past due fluid flush/bleed. Just the action, the clutch's engagement was smoother. And shifting was improved because in some way the past due fluid was (my theory) somehow causing the clutch to not disengage fully.

Even when I drove my Boxster for the last time and realized it needed a clutch -- the pedal effort was amazingly high but I guess I had gotten used to it then being without the car a month and then getting back in it really opened my eyes -- the engagement point didn't seem to be changed. Just as I mentioned the pedal effort really required a lot of force to overcome.

Given the amount of work you do on your car I'm surprised you don't have a lift, at least a portable (?) scissors lift that can get the car a foot or so off the ground and support it safely. Among other things I learned from my auto tech buddies was when the work they wanted to do on the car called for it getting the car in the air. While none had a lift in the garage they all had a nice floor jack and would roll it out and under the car and lift the car and get it supported on jack stands in practically no time. The problem with these cars is one can't (shouldn't) lift the car by any places other than the factory sanctioned lift points so a lift would be the best solution.
i just raise it on a floor jack and put heavy stands (stacked 6 x 6 PT actually) under frame locations. There are actually lots of places that are very strong (stronger than the suggested factory tabs in fact) and not too bad to locate something under. Nice and solid, but it is still very difficult to access the clutch bleeder, since it is way on the top of the tranny, with all sorts of driveshafts, tranny supports, and other stuff in the way. Worse, there is only room to swing a wrench (11mm) about 25-30 degress, which further complicates the job. Finally, while getting the car up 8-10" helps, its a far cry from real lift access as you note. Other jobs that are complicate are those that require a big lever to swing under the car. That simply takes space.

Grant

Grant gee-lenahan-at-vee-eff-email-dot-net
if you are doing new construction, make sure your slab is at least 4" under where the posts go for the anchors to seat properly.

My 30 yr old garage had just under 4" of concrete where I put my lift, and I had to cut out 2 footings and pour new concrete for the lift. Each post now has a 3'x4'x 12" deep footing under wear they sit. The footing is keyed into the existing slab. It's been working well since 2011.
Sorry, only registered users may post in this forum.

Click here to login