Gear oil level and change- New owner

Yes and Yes.

Mine are allen head plugs that fit pretty close to flush with the case.

Rocky

Thanks Rocky. I think I'll go out and try to scrape a knuckle or two.

Steve, as a help, the stock fill and drain plugs are 17mm and a VW has the exact same size hex. So there are cheap VW drain sockets available, or you can shorten a metric allen with a sharp hacksaw. Be prepared with a drip tray: it's a sloppy job trying to get lube into the side of the cases with a flexible funnel or a lube pump.

The trick is, fill until lube starts drooling out. Stop for a few minutes, then continue to fill. It may take 3-4 tries before the cases stay filled to the bottom of the fill plug. There are many internal passages and cavities and 90-wt doesn't flow very fast. The books say a ZF holds 3-1/2 liters of 80W90, but you won't be able to put that much in unless it's a brand new bone dry assembly, as the same problem with cavities and passages happens when draining a ZF. You might only get 2-1/2 L. back in. Remember: too much lube only makes a big mess while too little wrecks ZFs.

Jack,

Is there any point in overfilling a ZF? If so, how much extra gear oil would you recommend adding? I have a "flipped" M1 ZF, with a filler on top of the case, which was previously the drain plug, so overfilling is pretty easy.

I would avoid intentionally overfilling, and your dipstick is a valuable help there. I only mentioned it to not make it sound as if the amount was absolute. Pushbutton Panteras and 'Gooses got a dipstick as well as yours. I added a right-angle metric fitting to our stock early 'Fill' port, then ran a 6" long hose up level with the trans case top and added a cap with a weld-rod dipstick. Sitting for a few hours, the lube eventually finds its level & can be neatly topped up if needed. My ZF also got a temp gauge sender installed, and a 450-mile run to 'Vegas one year at 'somewhat illegal' speeds only brought the gear-lube temp up to 188F- barely enough to drive off condensation. Silver State runners tell me their ZFs get 'hotter' than that but no real numbers mentioned.

So excess lube will expand under heat and if there's a substantial extra amount, some may come out of the upper vent & make a mess of the whole rear of the car, but shouldn't otherwise cause much problem.....

Note the '80-up 'M-1' ZF variant has a different diff-case (reinforced over the ring gear & heavier; also known as the Super-ZF), and if it also has the M-1 trans, all the shafts, bearings and maybe the seals are larger in an M-1 than a '71-'76 ZF. The various sections (diff-case, trans-case and end-cap) can be interchanged but not the separate gears, as I understand it. Road-racers love the Super-ZF but Jr Wilson successfully ran a stock '73 ZF behind his 900-horse Boss-429 monster in dozens of Silver State races without breakage.

Reason I mention this is, I don't know what lube volume BMW or ZF specified in that transaxle variant. Might be a little more, or less; Lloyd would know, or whoever flipped the ring gear for you. Mangusta ZFs take less lube than the Pantera, but those cases are physically smaller & lighter. The 'Fendt Roller'- a paving machine with a ZF, has an external 1 qt(?) reservoir that one Swedish Pantera owner added to his car.

Thanks again! When you screw the plugs back in, do you suggest any type of sealer or anti seize or is it best to install them dry?
Also Boss wrench, I read one of your archive posts about cleaning/lubricating the shift shaft guide under the l/h header; great suggestion! So simple and what an improvement.

quote:

Originally posted by Bosswrench:
Steve, as a help, the stock fill and drain plugs are 17mm and a VW has the exact same size hex. So there are cheap VW drain sockets available, or you can shorten a metric allen with a sharp hacksaw. Be prepared with a drip tray: it's a sloppy job trying to get lube into the side of the cases with a flexible funnel or a lube pump.

The trick is, fill until lube starts drooling out. Stop for a few minutes, then continue to fill. It may take 3-4 tries before the cases stay filled to the bottom of the fill plug. There are many internal passages and cavities and 90-wt doesn't flow very fast. The books say a ZF holds 3-1/2 liters of 80W90, but you won't be able to put that much in unless it's a brand new bone dry assembly, as the same problem with cavities and passages happens when draining a ZF. You might only get 2-1/2 L. back in. Remember: too much lube only makes a big mess while too little wrecks ZFs.

Bosswrench , i just did a oil change and i could put in approx 3.3 liters ... so perhaps my ZF ( dash 2 ) drains better ?? don't know how much came out , i drain it in a typical garage catch reservoir . Oil was still very clean , only some minor metal around the magnet.

Your '86-87 Pantera #9425 may have the so-called 'Super-ZF. The factory ZF tags don't reflect it but if the diff case has a large curved flat piece on top that looks like added reinforcement (but is factory-cast), its an M-1 transaxle. ZF designed it as an upgrade for the turbo's torque in the early '80s for the BMW M-1s. That car had a far shorter production run than anticipated so some late Panteras got that box instead of an early assembly, who's rights etc had already been sold to Roy Butfoy in CA.

The diff-case is different due to the visible reinforcement, the gears are bigger and stronger and the mainshaft is larger with bigger bearings. As I understand it, the M-1 diff case can be swapped for an early case and transmission ass'y, but none of the transmission internals will swap to an early transmission case without machining. May have a different R & P ratio & tranny gear ratios, too. And being different, it may hold more lube. The 'Super-ZF' is quite popular with racers due to the overall heavier-duty parts.

Or maybe you just got lucky in draining it!

do you see anything related M1 ??