1999 Boxster manual transmission fluid change

[Vidyashankara]

This was also $50 a liter. I bought 3 bottles today. My 5 speed transmission should take 2.25L of this fluid.

[Vidyashankara]

I did the fluid swap yesterday. Went well overall..

The old fluid looked very good. I was expecting black gunk to flow out, but it was nice and clear. It did have an odd smell.

Then I added the new fluid till it overflowed a bit. Then started the engine, let it run for a while in all gears, then i added more fluid till it started to leak out. Then I torqued the fill plug.

I thought it was easier to change gears immediately yesterday. But today when i took it out, it wasn't as smooth as yesterday after the change.. maybe takes a while to work?

I used PN 00004330549 for the transmission fluid.

[rick3000]

You overfilled it, it is supposed to be 11mm below the fill hole. See the DIY:
Porsche Boxster Differential / Manual Transmission Fluid Change - 986 / 987 (1997-08) - Pelican Parts Technical Article

[Vidyashankara]

>>>Replace the bottom plug on the transmission, but don't tighten it too tightly (18 ft-lbs or 25 Nm maximum). These plugs do not have a tendency to leak (transmission oil is thicker than engine oil). If it does leak later on, you can always tighten it a little more. Now, add transmission oil to the case. The best method of doing this is with a hand operated oil pump. These are available from most auto parts stores and attach to the top of the plastic transmission oil bottle. They work very similar to the liquid soap dispensers you find in most bathrooms. Pump the transmission case full of fluid until it just starts to run out the filler hole. Replace the filler plug and clean up the few drips that might have run out of the hole. Tighten down the filler plug in a similar manner to the drain plug.


ISnt that to check the fluid level? The procedure asks to fill the oil until it overflows?

[Anker]

The instructions for the 5 and 6 speed transmissions are different.

The 11mm below is for the manual 5 speed transmission.

The fill to the bottom of the fill hole is for the manual 6 speed.

[rick3000]

That Pelican guide should really be a little more explicit about which instructions are for which transmission. I double checked my Bentley manual, and for the 5-speed it should be 11mm below the fill hole.

[Vidyashankara]

Originally Posted by rick3000

That Pelican guide should really be a little more explicit about which instructions are for which transmission. I double checked my Bentley manual, and for the 5-speed it should be 11mm below the fill hole.

Damn!! Is overfilling bad?? I can't get back to the lift for atleast 2 weeks! Will it be ok?

[Anker]

Overfilling puts an extra load on the gears inside the transmission. You can draw it down without a lift. Floor jack and jack stands do the job.

[Vidyashankara]

Originally Posted by Anker

Overfilling puts an extra load on the gears inside the transmission. You can draw it down without a lift. Floor jack and jack stands do the job.

I will try and do this in the next couple of days. I still need to remove the aluminum tray and diagonal brackets covering the transmission right?

[paulofto]

Originally Posted by Vidyashankara

I will try and do this in the next couple of days. I still need to remove the aluminum tray and diagonal brackets covering the transmission right?

Save time, effort and a lot of potential alignment issues and drill an 2" diameter access hole in the tray. You'll be happy you did.

To remove just a little fluid, remove the fill plug and jack up the from end, some fluid will leak out the fill hole and then level the car and see if the 11 mm difference is met.

[Vidyashankara]

Originally Posted by paulofto

Save time, effort and a lot of potential alignment issues and drill an 2" diameter access hole in the tray. You'll be happy you did.

To remove just a little fluid, remove the fill plug and jack up the from end, some fluid will leak out the fill hole and then level the car and see if the 11 mm difference is met.

Awesome, thanks! Can you explain the potential alignment issues?

The hole will give access only to the drain plug right? I am not sure if i can access the fill plug without remove the tray.

[paulofto]

You should be able to get at the fill plug with the tray in place. It may be a bit awkward but accessible. The fill hole for the 6 speed is more accessible.

The alignment issue comes into play when the tray is removed. It is a bear to get back in and align it with the bolt holes in the two support arms. Wrestling it back in is a pain and could result in things not lining up correctly.

[rick3000]

I spent a few hours researching the transmission oil for the '99 before I changed mine. Porsche really went all out on the early five-speed's and the oil is in fact specific to the transmission. It's a shame most dealers will try to sell people the wrong fluid, because they don't stock the 20L drum. Don't trust the parts guy at the dealer!

Originally Posted by Vidyashankara

Awesome, thanks! Can you explain the potential alignment issues?

The hole will give access only to the drain plug right? I am not sure if i can access the fill plug without remove the tray.

The plate is part of the suspension system, it acts as a brace between the rear suspension, and when you remove it, you can change the alignment of the car. If you choose to remove it and not drill a hole, use jack stands and not ramps. By taking the weight off the wheels you will reduce the chance of messing up the alignment. When I removed the plate I used stands, and when I had my alignment checked afterward it had not been affected.

[JFP in PA]

The larger issue with overfilling the gear box is oil getting onto the clutch via the input shaft when the oil gets hot.

[Anker]

Not sure. I have the 6 speed and the fill plugs are in different locations.

[Frodo]

I just noticed that the Mobil synthetic transmission oil question was already addressed earlier, so I probably don't need any response on that. OTOH, if anyone's used it and found absolutely no decrease in performance or smoothness of shifts, I'd be interested in hearing about it.

[JFP in PA]

30 to 40K miles is the optimum window, depending upon how the car is used (track cars change sooner).

[Frodo]

I'd listen to him...he kinda knows this stuff pretty well..

New info: I contacted the folks at Sunset, asking about their transmission oil. He replied, "This is the Mobilube PTX 75w90 transmission fluid. Porsche only sells it in 20 liter containers so we break it down in to individual liters for our customers."

I was thinking the "Porsche stuff" was a Shell product. I'm not sure exactly what constitutes OEM transmission fluid in P-cars anymore. Is this Mobil product the one that is so much better than the other oils out there? The stuff that you, JFP, have had customers drain out other transmission oils to put in?

[JFP in PA]

Originally Posted by Frodo

I'd listen to him...he kinda knows this stuff pretty well..

New info: I contacted the folks at Sunset, asking about their transmission oil. He replied, "This is the Mobilube PTX 75w90 transmission fluid. Porsche only sells it in 20 liter containers so we break it down in to individual liters for our customers."

I was thinking the "Porsche stuff" was a Shell product. I'm not sure exactly what constitutes OEM transmission fluid in P-cars anymore. Is this Mobil product the one that is so much better than the other oils out there? The stuff that you, JFP, have had customers drain out other transmission oils to put in?

Porsche currently has two approved 6 speed lubes, this is one, the other was a Shell product. The early 986 base cars with a 5 speed used a totally unique product which was made by Burmah, which is also a Shell subsidiary.

[Frodo]

Okay, now we're gettin' somewhere.

So, when people say it's best to use the Porsche transmission oil, that it's so much superior to the competition, that would apply equally to both the Mobil and the Shell products?

BTW, I have no axe to grind here...I'm just trying to figure out what's going into my gearbox.