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Topic Review (Newest First)

  • 02-11-2006, 06:30 PM

    DON'T use a torque wrench!

    I own a 3.0L Z3, and was just checking out this board because I like the Z8 a lot...

    Anyway, I don't know anything about Z8 transmissions or differentials, but I know that I'm NOT going to use a torque wrench on the drain/fill plugs for any car I ever work on again...

    The first time I changed the diff and trans fluid in my Z3 I cracked the rear diff cover, which I had to replace, and later found the trans drain plug threads had cracked as well resulting in a leak. Luckily I was able to use liquid aluminum type stuff on trans crack to seal it and it all worked out. Yeah, this was an unpleasant 'learning' experience on what happens when you overtighten things...even though you used a torque wrench and the proper torque specs. I would really suggest just using some thread sealant on the trans plugs and tighten the plugs on the trans and diff with a short-handled ratchet until snug.

    for what it's worth...

  • 01-11-2006, 11:17 AM
    Z8Eldred a.k.a The Mudman

    Should be fine. My dealer has been changing mine

    since 2001 with no issues.
  • 01-11-2006, 07:19 AM

    Re: Oil and Differential Fluid Change

    Thank you very much. I too have never used a torque wrench for an oil drain plug but I am a bit apprehensive now given your previous warning. I guess I want to be extra careful with this plug.
  • 01-11-2006, 12:52 AM

    Re: Oil and Differential Fluid Change

    I haven't pulled an oil pan plug for quite a while so I can't remember what size threads it has but the correct torque spec is as follows:

    12mm threads : 25Nm
    18mm threads : 35Nm
    22mm threads : 60Nm

    Just keep in mind that there are only a very few threads in the oil pan and that is why they tend to strip out. I don't know if they will strip at the factory recommended torque or only when a gorilla does the tightening. Frankly, I don't use a torque wrench for oil pan drain plugs, rather I tighten by feel based on years of experience. Just be careful and if the plug doesn't tighten up steadily but feels like it just wants to keep turning, STOP!

    Oil filter cap gets 25Nm

    Differential drain plug gets 65Nm
    Differential fill plug gets 60Nm
    Grease Monkey
  • 01-10-2006, 02:25 PM

    Re: Oil and Differential Fluid Change

    Thanks guys for the quick and informative replies!

    Unfortunately I already have removed the oil drain plug so I'll have to take the risk of not striping it out when I put it back in. I guess I will buy the oil change pump for future oil changes.

    Haven't got the filter replaced yet. Nor have I started on the diff change.

    Do you by any chance have the torque spec for the oil plug and diff plugs?

    Thanks. -Chris

  • 01-10-2006, 01:24 PM

    Beat me to it. Your write up is better anyway.

  • 01-10-2006, 01:22 PM

    Heating the oil is always a good idea to (m)

    make it flow out better. Just drive the car around the block. Obviously, you will need oil. Search the archives for GMs extensive write-ups, but the concensus was that Red Line 75-90 gear oil was the ticket.

    You will also need some type of pump to get the new oil into the diff. I bought one from BMP.

    Good luck.
  • 01-10-2006, 01:16 PM

    Re: Oil and Differential Fluid Change

    I do not recommend changing the oil on your Z8 from below. The threads for the drain plug in the oil pan are prone to stripping so you must take great care when torquing the plug back in. I recommend the use of an oil suction device like the one sold by Griot's Garage. This allows you to completely replace the oil without risking those stripped threads. The following instructions apply to an oil change using a suction device. If you want to drain from below, just substitute drain plug removal, copper washer replacement, and drain plug torquing after the oil filter section.

    Engine should be warmed up first so the oil will flow easily when you suck it out. Before proceeding, get a rag or small pan to catch dripping oil from the filter when you remove it. Begin by unscrewing the black plastic cap from the oil filter canister located on the driver's side of the engine compartment, near the windshield. The nut on top of the cap is a 36mm. If you don't have a socket that big, you can use an adjustable wrench; just be careful it doesn't slip. When you remove the cap, which has the filter attached to it, most of the oil will drain back into the oil pan but some will remain in the canister. Unsnap the old filter from the cap by pulling on it. Now pry off the large O-ring which is located in a groove near the top of the cap and replace it with the new one that came with your oil filter. Use a little oil on your finger to lubricate the O-ring so it has a thin coat on it. Now snap the new oil filter onto the cap and make sure your hear it "click" in place. Now use your oil evacuator to suck out any remaining oil in the oil canister, then pour in enough new oil to fill the canister about half way. BMW skips this step but I want the oil system to get pressurized as quickly as possible when starting the engine so I like to "prime" the oil filter canister. Now put the cap with attached oil filter back into the canister and snug it all the way down. Keep an eye on the O-ring to make sure it doesn't get pinched. Now pull out the dipstick and stick your oil evacuator's tube down into the engine's sump until you feel it bottom out. Suck out as much oil as possible. Remove the evacuator's tube, put the dipstick back in, and fill the engine with your favorite oil. Fire it up, make sure the engine oil light goes off quickly, let it run for a few minutes, check for any leaks at the canister, then turn the engine off, wait about a minute or so, then check the oil level on the dipstick. Add oil if necessary. Do not overfill. Pat yourself on the back.

    Despite BMW's claim that the fluids in the Z8's transmission and differential are good for the lifetime of the car, I don't buy it. I don't believe any lubricant can maintain its effectiveness indefinitely. Rather, I suspect lifetime fluids are part of a marketing effort aimed at competing with other brands offering easy long-term maintenance schedules as a selling point. Unfortunately, by the time we find out if lifetime fluids really do offer adequate protection, our cars could be out of warranty.

    With this in mind, I have drained the transmission and differential fluids from my Z8 and replaced them with Red Line synthetic fluids, which I believe are the best available. I will replace these fluids on a regular basis, not because they won't last as long as BMW's fluids but because the cost is minimal and the insurance against wear brings me peace of mind.

    A side benefit of this fluid swap is that there is a noticeable improvement in the ease of shifting the tranny. The last hint of notchiness (most was eliminated by the UUC short-shift kit) is now gone and the shift action feels smoother and quicker.

    I used Red Line D4 ATF in the transmission (2 Qts.) and Red Line 75w90 Gear Oil (1.3 Qts.) in the differential. By the way, you will need a 14mm allen wrench to change the fluids in the differential. Changing fluids is always easier when they're warm but it is not necessary with the transmission or differential. Insure car is level, then refill until fluid runs out of upper hole. Replace plug and you're done.
    Grease Monkey

    Grease Monkey
  • 01-10-2006, 10:33 AM

    Oil and Differential Fluid Change

    I just installed a four post lift in my garage and I am planning to change the oil and differential fluids in my '01. Any hints or "gotchas" that I should know about? Does the differential fluid need to be warm like the engine oil when it gets changed?

    Any links to DIY information?


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