I've been told that my  Pantera  # 1791 has an M1 Transmission identified by the Flat Shaped Bell Housing.

The ID tag states that it is a Dash 2.

Does anyone know what the difference is ?

21ZF Tag

 

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Original Post

That thread references dash 1 to dash 2, what the OP has is an M1 i.e. a later ZF from the BMW M1. The casing certainly appears to be that of an M1, but the M1 has the ZF in the same orientation as the GT40 (upside down to the Pantera) and it would have had CV axles, so not sure why someone went to all the trouble of retrofitting it for a Pantera. That said the serial number is quite early, so I wonder if someone used an M1 case to rebuild an older ZF?

This thread is more relevant;

https://pantera.infopop.cc/topic/m1-zf

Julian

Further to Julian's comment; it's likely your ZF's case was replaced at some point in its life with an M1 case. Years ago, the M1 case was a Hall Pantera catalog item. The ZF's redesign took place during the development of the BMW M1, which was first sold in 1978. I have an M1 ZF in my Pantera but my serial number is about 7,000 higher than yours. 

M1 gearbox is not possible. It use a diffrent imput shat, wich is longer than the "pantera" zf.  

You have to change the shaft and some other parts to mount it on a pantera

ps . the housing was a later thing on the zf - but there are several Panteras especially gt5s versions, they have those housings. Not only BmW M1 !

But as I said, the BMW M1 Imput shaft to the Pantera  is total diffrent.  ZF 25 DS/1 to ZF DS25-2 is a smaler pilot baring . 

PB

Peter, if the M1 ZF's input shaft is, indeed, longer than a -2's, the extra length would not be on the engine end of the shaft. The two are not interchangeable although I was not aware that length was the issue. The pilot shaft is smaller than a -2's but the rest of the input shaft is more robust. I can most certainly confirm that an M1 ZF can be installed in a Pantera without issue.  

I purchased my M1 ZF in 1999 from Roland J. in Germany. If I recall, he had just bought 20 or 30 of them from BMW Motorsport. They were brand new and in BMW shipping crates. At the time, my -2 was with Lloyd Butfoy, about to be rebuilt. We (Lloyd and I) determined it would be cheaper to buy the M1 ZF and convert ("flip") it for use in a Pantera than it would be to have my old -2 rebuilt. That included a taller R&P. The cost of an M1 ZF back then was less than 9,000 DM. Roland sold every one of them in a matter of hours! 

David, great to know this, I only meassured some M1 boxes during I repair them.

So I see that the shaft is longer and maybe the theet from the clutch are also diffrent. The Gearboxes from the M1 I rebuilt in the past have also diffrent gear ratios, maybe because of my customers are racer, so they changed some ratios.

Good to know that it is only a small thing to covert them to a Pantera .

Have a nice day, sorry for my terrible english.

 

Peter, the splines on the input shaft are standard BMW. I've always used McLeod discs. When I order them, I simply pick the disc I want and specify a BMW hub. I was told by more than one person the input shaft had the same splines as a -1 ZF but that turned out not to be the case. 

Having now just caught my breath I want to thank all.

I'v had the car for less than a year and the learning curve has been incredible.

When BMW contracted with ZF for transaxles to be used in the M1, the agreement was, ZF would update and strengthen the units. More specifically, the case and input shaft were strengthened. Also, the gear and synchro ring design was updated. Oddly enough, they still didn't see fit to safety wire the ring gear bolts! This became the standard ZF transaxle from that point on. Years later it became the RBT 5 speed transaxle except the ring gear bolts finally came safety wired!  

As far as gear ratios are concerned, the R&P was still a 4.22:1. The first three gear ratios were slightly lower (since the M1 had a high revving six cylinder engine) but 4th and 5th were both taller than in a "Pantera" -2. I think DeTomaso must have had a bunch of ZF -2's in inventory because the only Pantera's I've seen with the M1 version of the ZF were Si's. 

When I had an M1 ZF prepared for use in my Pantera, I had Lloyd install a 3.77:1 R&P, since the last thing I wanted was lower gearing in the first three gears!   

Sounds like a good combo for a high torque motor, taller gears all the way!

What we’re the 4th & 5th gear ratios in the M1 box?

Thanks

Rocky

 

 

 

 

I reached out to RBT but I wish there was a way that I could research the History of the M1 ZF in # 1791.There probably is no Prova Mo for ZFs

Last edited by thrillrider

Rocky, I mis-spoke when I wrote 4th and 5th were taller in the M1 box. Sorry; it's been 21 years since I bought it!  Both are the same as the standard -2 ZF. If I ever had mine apart for any reason, I'd replace 4th with a 0.846 and 5th with a 0.642. Those are the ratios RBT uses. 

The pair of ZF's on BAT that Larry mentioned, are neither M1 nor Pantera variants of the ZF transaxle.  I suspect they are from a mid-eighties Lancia Rally 037, judging by the Pantera orientation of the gearbox and the gear ratios both units are fitted with. You could physically install one into a Pantera but you'd need to replace a bunch of gears and the R&P. You'd also need a Pantera shifter mechanism, T/O bearing parts and CV joint conversion kit. Because these units were likely used for racing, who knows what else you'd find (damage?) once you got inside! 

Last edited by davidnunn

To supplement what David said above, ZF cases TIG-weld nicely so the chopped up ZF is indeed fixable. But the machined surface on the case front will warp into a potato chip from weld heat, so better have a big lathe or a mill & rotary table available to re-true the surfaces after repairing. Or a bellhousing won't fit square. Then you can start building your own throwout nose to fit the flattened spot, as trying to reweld that area will distort the front mainshaft bearing recess, requiring even more machining. Personally, I think I'd run the cut case as-is, behind a moderate power engine but NOT with a high-horse V-8. Sawzalls should require a license for some people.....

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