Inversion ZF 5DS-25/1 transaxle and bell housing

Hello all,

I’m new to this forum and I’m currently trying to find all missing information to get my project started. My main goal is to try to keep the car as original as possible and therefore would like to use the ZF 5DS-25/1 transaxle (it seems that the /2 version is always used, and not the /1 version, any reasons?).
My main questions are:
1/ Is the ZF 5DS-25/1 really similar or the same to the one used in the GT40 Mark 1
2/ Does somebody have some documentation how to perform the inversion of the ZF 5DS-25/1 transaxle
3/ Can I use or will the ZF 5DS-25/1 fit the original GT40 bell housing

I know, a lot of questions, but I’m keen to get all my technical ‘problems’ solved before I get my garage filled with parts.


D

PS: Tried to find something about ZF inversions via the search option but…

D

As I understand it, the original GT40's ran ZF 5DS 25-O. The dash 1 and dash 2 were put primarily in the Pantera. The dash 1&2 as set up for the Pantera are actually "running upside down" compared to the original dash 0 design. I'm going from memory but I believe the dash 0 had a 4 bolt bell attachment and later versions went to a 6 bolt. 2 people to talk to are; Lloyd Butfoy of RBT transmissions who now owns the rights to the 3 mentioned models. http://www.rbttrans.com/ Cory Gelhing of Collectors Choice who is a ZF factory certified tech who can preform this operation, and who has prepared many of the boxes for the original cars. Cory Gehling [[email protected]]

Parts for the dash 0&1 are becoming extremely scarce and expensive.

There is a guy that advertises in Hemmings.com who deals in the original GT40 ZF's.

Hope this gets you started.

Andy

Thanks Andy, this will help me further. Didn't know for example that the GT40 was running the dash 0 transaxle.

D

You might consider the -2 version of the ZF gearbox; the one which came in the BMW M1. These are reputed to be sturdier, and they do not have the sequential shift arrangement inside the gearbox that a lot of folks would rather not have.
Lloyd at RBT can sell you a rebuilt ZF unit ready to go and put in a GT40. He has done more of them than anyone, no doubt. He does most of the ones for ERA, if I am not mistaken. He has been around a long time and has a good reputation.

Hi Didier
To answer your first question as to why most people don't use the 25/1 box is that they are extremely rare and therefore don't appear very often. I had never heard of a 25/0, all the boxes fitted to the original cars had an NR prefix to the number, maybe these are 25/0. Also the early boxes can be identified by not having the extended side plates and cross bolts in the 'top' cover. Just to confuse things, my box is from an early Pantera and is a 25/1 with the extended plates and cross bolts!. With regard to inverting, try and get hold of a ZF 'Assembly, Maintenance and Operators Manual'. In it you will see that there is a small trough under the gear cluster that directs oil through to the crown wheel. This is only fitted to the box when used with the removable cover plate to the top, (the correct way up!).Also the side plates that hold the output shaft bearings have to be modified to allow the oil into the top and the existing ones now at the bottom should be filled in. Apart from reversing the crownwheel, the only other thing to do is to drill a few holes into the bottom of the wall between the main gearbox and the crownwheel housing to allow the oil to flow through.

Hope this helps.

Brian.

Thanks guys, I will contact Lloyd. If have seen on their web page that there are 3 types of 5DS-25 transaxles: /0, /1 and /2.

D

Having just completed the inversion process for a /2 box, I may be able to help. I found a lot of information about the inversion process and Lloyd at RBT was very helpful. I also purchased the ERA assembly manual for their GT40, as it explains the entire process of inverting the ZF and also explains the differences between the various types. ERA can help with the slave cylinder and mount as well as the throw-out bearing kit which includes the throw-out bearing, bearing carrier, and pilot bushing. You can view the ERA manual for free on their web site but the pictures are deleted. By purchasing the manual you can view the pictures as well. Hope this helps.

Yes I agree with Pat.The ERA manual has a lot of helpful info on ZF inversion and clutch/flywheel/starter as well.ERA sell a bellhousing for /2 which incidentally is 7 bolt and has a flat bottom to allow low engine/drivetrain positioning in chassis.I reckon you should also obtain the ZF workshop manual if you plan on doing any internal work yourself.See my post on this forum (18 months with a ZF)if you need encouragement.I have a BMW M1 ZF which I am lead to believe is a /2 with a stronger case and already inverted for GT40 use.There is a lot of ZF info on the pantera forum and you'll find gear ratios listed for /1 and /2 models.The /1 had a .86 fifth gear( not so good for touring) and /2 had .705 fifth and 4.22 diff ratio(also not great for touring)so a lot of pantera owners have changed crown wheel and pinion to 3.77:1 (much better for touring on the road.Good luck and a very good Idea to plan like you are doing.I did a lot of planning on the ZF as a large part of the build revolves around it.And even after the car was finished I still had to alter the internals to suit my use for the car which is on the track.
Ross

Hi ya'll,

Maybe I can provide a little history.

The original Ford GT40's production race cars primarily used one of two gearboxes.

The GT40's were powered by 289 cid engine and used a Colotti 4 speed transaxle. Colotti's were the only viable and available gearbox in the early production days. A few ZF transaxles were used when they first became available in 1965. The small block cars were not competitive and had a tendency to tear up the gears.

The MK II's, "J" car, Mirage and MK IV's used the T44 4 speed transaxle. These gear boxes were especially fabricated to accommodate the 427 cid big block engine.

Several of the "J" cars used a Ford torque converter/2-speed manual gearbox.

The ZF transaxle could not handle the torque of big engine. This is because the ZF gears are helically cut (synchromesh) which makes for easy shifting and low noise but they have poor power transfer.

The GT40 MK III's were specially made for street use. They used the ZF 5DS25 transaxle attached to the 289 cid engine. Only seven MK III's were built by Ford.

Of the original Ford GT40's production race cars, eleven were converted to "GT40 road cars" these also used the ZF 5DS25 transaxle mated to the 289 cid engine (chassis numbers 1013, 1014, 1021, 1023, 1025, 1028, 1030, 1033, 1035, 1036 & 1049 - 1049 was subsequently re-converted back to a race car).

I can't say with absolute certainty which ZF variant (0, -1, or 2) was used in the MK III's or "road cars" but I strongly believe they were ZF 5DS25-1's.

Holman & Moody was assembling the GT40's during its heydays. Ford made a business decision to get out of the racing business. Holman & Moody maintained the cars for a while but as the GT40's became less competitive they eventually discontinued their support. When Holman & Moody dropped out they sold their remaining spares, including T44 and ZF gearboxes.

I purchased a rebuilt ZF 5DS25-1 from Holman & Moody in 1973 for $500. This gearbox went into a hand fabricated car of my design (see attached).

I knew that maintenance/repair of the ZF could be problematic so I bought spare for $800 in the late 1980's. It came out of a Lola T70 and is a ZF 5DS25. Since there is no versioning number on this transaxle I assume it's a -0.

Both of my transaxles are held to the bell housing with four bolts. They also have two mounting tabs on the top of the gearbox case.

I have a ZF factory service manual for the ZF 5DS25-2. It shows seven bolts are used to hold the gearbox to the bell housing. Otherwise the -2 appears to be identical to the -1 except that its orientation is rotated about the drive shaft axis by 180 degrees.

Hope this info helps!

Dr. Mike