Gear oil change....

I changed my '07 2.7 5 speed gear oil over the weekend. Car has 54k miles. Used Mobil Delvac Synthetic Gear Oil 75w90 from Lufteknic. I had a slight crunch from 1st to 2nd that I thought would go away. Crunch is a strong word and it really isn't that bad and can be eliminated with slightly more patient shifting. The crunch or click is still there. I read another post where an owner had the same problem and he also added LubroMoly MOS2 to the gear oil. I'm not much of an additive guy but wondering what or if I should do anything. Thanks, C.

This is a common problem on Miatas and my Miata was terrible from 1st to 2nd gear. The lube of choice to fix it is Motorcraft Full Synthetic Manual Transmission Fluid. I tried it and it worked wonders. Before the fluid change I could not get into 1st gear from 2nd, now it slides right in and 1st to 2nd gear shifts are noiseless. I don't know how it will work on the Cayman but its still a 75w90 so it couldn't hurt

Very interesting about the Motorcraft ... I'm actually waiting for someone to ask me why I didn't run Porsche gear oil. I bought my car at 32k and it has been pretty much the same since then so I felt there was improvement to be had. The Delvac oil has some strong testimonials by Luftecnic like factory fill in almost all Porsche Motorsports race cars. That doesn't mean it's good for the street but I thought it was worth a try. Now on my second day, the shifting is OK but there is still a bit of a click from 1st to 2nd. Everything else is good. C.

I had an issue going from second to third in my Civic SI. Amsoil Synthetic solved the problem. It shifts great now. However, I just looked on the website and they don't recommend one of their products for your car. Sorry Andrew

Mr Crispy did you lift the entire car or did you just lift the rear? And if you don't mind what type of wrenches are required for the drain and fill plugs?

front wheels on 8x8's and back on jack stands. The socket doesn't have a size on it (except Audi /VW 3357). It's a 12 point spline with a 16mm o.d. For the Audi , it's tamper proof with a hollow center. I highly reccomend drilling an access hole in the plate under the gearbox. I did it with a 2" hole saw. The hole's center is located about 3/4" left and 1/4" forward of the drain hole in the plate. C.

Great, I have a bit with a 16 mm triple square on one side and 17 mm hex on the other, used it on the VW's and I agree it seems like the access hole is a no brainer. Thanks for the info.

Sorry if I've missed this part in the discussion ... but where & how does one put the new oil in the manual transmission ... anyone have pics ? have '07 CS 6spd

Look here for pictures Pelican Technical Article: Boxster Differential / Manual Boxster Transmission Fluid Change - 986 / 987

If you're changing out the fluid with the car on ramps, jackstands etc (ie not amount of room under the car) here are a few tips that I found helpful. First off, before draining the old fluid, make sure you can access and remove the filler plug ! I use a small bubble level to make sure the car is sitting completely level. This is important because filling the transaxle to the proper level is contingent upon the car being level. If its not, you risk under or over filling. If you don't have much room under the car, use a generic handheld 1 quart fluid transfer pump. If you're using a modern synthetic fluid, they're much less viscous than older gear oils and pump fairly easily, although it will still take some time (plus you'll have to keep refilling the quart sized pump). Delvac is the current factory fill and is recommended because its formulated specifically to work with the carbon synchronizers used in current transaxles. Interestingly, it is clear and pours like water (hard to believe it has a viscosity rating of 75-90). It can be hard to find and fairly expensive ( Suncoast usually has it if you can't source it locally). The most difficult part is removing the aluminium cover underneath the transaxle. it is definitely worth drilling an access hole in it (now regretting I didn't when I had it off) to save time on future changes. Its not difficult to remove, just a PITA.

Has anyone tried a Motul brand in their manual gbx?

I used RedLine gear oil and noticed an improvement on shifting. I didn't have an issue before, but it shifts smoother since I changed it.

Crispy, I want to drill a access hole in my plate. How did you do this, with plate on or off the car? I'd hate to drill a (blind) hole using your measurements with the plate on the car and find out that I missed the mark. THX

Of course I felt exactly as you. Who wants to drill a random hole in their Porsche ? I drilled the panel on the car (that's the point right?) and checked by eye, the best I could, before I drilled and you should too. The pilot drill on my hole saw was set shallow (are you kidding?) and it was done and over with so fast it didn't hurt at all. The hole was centered perfectly. C.

I removed the plate when I changed my lube last fall. I didn't feel confident about the location and had read somewhere that the hole could weaken the rigidity of the plate. I kinda think that isn't a real issue unless the hole is very big. So, after removing it I loosened the fill plug (just in-case) then opened the drain plug . I was surprised at the force that the oil drained. And not straight down - but at an angle. It seemed to me that if I had drilled the hole, I'd be trying to clean-up a big mess on top of the plate. I'm sure I'd have to remove it in order to do a good clean-up. Anyone had a problem like this? I guess if you are going to drill, be sure to use a 2.5" or greater hole-saw. And be extra careful to center it.

Had the same issue when I had a Miata years back. I put in Redline Synthetic gear oil and it made a big difference! Very smooth as compared to the gear oil that came from the factory.

Thx again. Am going to try it today.

Worked out just fine. Could probably have used a 1.5" or 1.75" hole saw instead of a 2". Hardest part is getting to and removing/installing filler plug .

Yeap. There are four nuts and one bolt holding the long aluminuim chassis brackets in place. All of four nuts have to come off. I left the one BOLT (fifth attachment point) on the front part of the bracket just (in front of the tire/wheel) in place, but loosened it quite a bit. Then these brackets have sufficient play to swing aside to remove the aluminium tray. A side note, I had to adjust the height to level the car up front after the alum cover was removed. It wasn't even, and I didn't think much of it until when I started putting things back together. I found that the mounts/attachment points to reinstall the cover had moved as well. To get the cover back on, I ended up lowering the front of the car to the floor, perfectly level. Then everything lined up correctly. Meaning this cover is also part of the structure and likely increases rigidity. Other pictures show the location of the fill plug, this all taken from the driver side rear of the car looking toward passenger side. I couldn't see it until I got really close in after looking at a diagram posted elsewhere.

This article helped tremendously. Kudos to whoever created it.

Does anyone know the tightening torque specs of the transmission shield?

48 ftlb. Look here https://www.youtube.com/watch?v=4YYqPZ8W7l8&t=14s Minute 10:09 - 10:12 This is for 986 but it is the same for 987.

Thank you!

FYI... Had a crunchy 3-2 downshift. Changed oil and used Motorcraft . No more crunch.

Thanks husker boxster for the lead. Your feedback plus all the positive reviews I had read on various Miata forums convinced me to try out the Ford Motorcraft oil (XT-M5-QS) and I’m glad I did. Mine wasn’t crunchy but shifting was balky especially when cold and shift quality is significantly better after the switch.

Please post a rough sketch of the hole's location? Specifically, please indicate which direction is front or rear of car. 'Much appreciated. Thanks.

Thanks for the drawing! Big help when I did mine today. Never real confident drilling holes in expensive sports cars but it worked out great. Mobil 1 Delvac works very well.

I can't say I can recommend that Motorcraft oil in a modern Porsche . It is a GL-3/GL-4 gear oil designed for gearboxes. Our Porsches have a transaxle: the gearbox and the differential share the same fluid. Differentials experience higher pressures and need a higher level of protection, and Porsche spec'd a GL-5 gear oil for this reason. The Motorcraft oil may shift okay but it is potentially not providing sufficient protection for your differential. It's fine for something like a Miata where it only goes in the gearbox. If you change the oil, I would suggest either going with the Porsche stuff or with something like Redline 75W90NS (which is a GL-5 gear oil that's specifically designed to work well with transmission synchronizers.) I used the Redline when I changed mine and it's shifting fine, though it was shifting fine with the original Porsche oil too.

Gubi, thank you for the information. I was not aware there was a specific lubrication designation. I did some checking and found these specs for Motorcraft . https://www.fcsdchemicalsandlubrica...roduct.asp?product=SAE+75W-90+Synthetic+Axle+Lubricant&category=Transaxle Fluid It appears to be GL-5.

There is more than one part#: Earlier mentioned Ford Oil: XT-M5-QS (not GL-5) Oil you listed: XY-75W90-QLS (GL-5) You didn't list the particular oil you used in your earlier post...going to lead to confusion.

Yep. The XY-75W90-QLS is a GL-5 differential lube. Might be okay for transmission synchronizers in a transaxle but unclear: a lot of GL-5 lubes have additives in them for the LSD that tend to mess up synchronizer action. The XT-M5-QS is a GL-3/4 gearbox lube. It states " is also recommended for older transmissions including rear wheel drive [i.e., a transaxle] that recommend GL-3 and GL-4 type gear oils" which is not what a modern Porsche has. https://www.fcsdchemicalsandlubricants.com/main/product.asp?product=Full+Synthetic+Manual+Transmission+Fluid&category=Transmission%20Fluid To be fair Porsche doesn't explicitly state GL-5 anywhere I can find. But the OEM Mobilube PTX is GL-5, and all modern differentials use GL-5. Is your diff going to wear excessively with GL-4? Dunno, but I wouldn't try it given that there are better options. This stuff is complicated. I just happen to know a lot about it because I had an Alfa Romeo Milano with a tranxaxle and Alfa synchronizers are super-dodgy, so I've tried a whole bunch of oils over the years. In the Cayman I just used the Redline 75W90NS because I know it meets specs, works pretty well (at least, in my car), and is about half the cost of the Mobil stuff. If you try it, be sure to get the "NS" stuff. The regular 75W90 has the aforementioned LSD additives that mess with shifting. https://www.redlineoil.com/Content/files/tech/75W90NS_GO_PROD_INFO.pdf For the record, when I swapped the original oil at 56K in my 2010CS it was pretty darned clean, so unclear that I really had to replace it.