Top Loader gearbox into 1980 M90 635 - any experience?

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Mamod17
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Top Loader gearbox into 1980 M90 635 - any experience?

Post by Mamod17 »

I have the opportunity to install a top loader gear box in my 1980 M90 JPS tribute - doesn't anyone have experience with this? Which bellhousing would be compatible? Need for Motronic pickups etc? I believe some BMWs in the 70s came with top loaders but I can't find any info. Thanks in advance!
1980 JPS635csi Group C Tribute
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zinnocoupe
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by zinnocoupe »

Top loader?? You mean a Ford toploader? I guess anything is possible but it would be the spline count and size that would be the problem.
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bpoliakoff
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by bpoliakoff »

Spline count doesn't matter as you order the clutch per the car the trans is originally for and the splines will match up. The bell housing is the issue and why in the world would a guy want to replace a 5 speed with a Ford 4 speed top loader although it is virtually bullet proof.
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zinnocoupe
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by zinnocoupe »

Yes I guess you're right about the spline Bert. Still the clutch plate would have to match the pressure plate and flywheel. Sounds like a headache to me
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by bpoliakoff »

I think this gent doesn't know what he is doing. As to matching the fly wheel you can get a clutch plate in various diameters or have one made not expensively to match the BMW pressure plate.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
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Mamod17
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by Mamod17 »

bpoliakoff wrote: Tue Dec 01, 2020 11:13 pm I think this gent doesn't know what he is doing. As to matching the fly wheel you can get a clutch plate in various diameters or have one made not expensively to match the BMW pressure plate.
Ok so I wasn't far off - apparently it's a "toplader" - a ZF S4-18/3. Is there anything special about this compared to later gearboxes? The linkage setup/ratios? 😁
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1980 JPS635csi Group C Tribute
1986 635csi 5speed Alpine White M-Tech Aust Del
2001 325ci Auto Orient Blue

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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by bpoliakoff »

Not to be rude , but that is why the confusion. That is not what a top loader gear box is when commonly referred to. That is just the way the shift linkage is in a ZF gear box.A top loader really refers to a Ford 4 speed of the Muscle car years. If I am correct, I have only seen one other of those ZF gearboxes and it should be a close ratio box and bolt up to the M30 bell housing but you will have to check measurements out yourself as this is not a very common gearbox.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
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zinnocoupe
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by zinnocoupe »

OK this is very interesting. I think I've heard of this. Never seen one though. Is the input shaft the same as the getrag? Do you know what car this came out of? 5spd?
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
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Mamod17
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Re: Top Loader gearbox into 1980 M90 635 - any experience?

Post by Mamod17 »

bpoliakoff wrote: Wed Dec 02, 2020 3:46 pm Not to be rude, but that is why the confusion. That is not what a top loader gear box is when commonly referred to. That is just the way the shift linkage is in a ZF gear box.A top loader really refers to a Ford 4 speed of the Muscle car years. If I am correct, I have only seen one other of those ZF gearboxes and it should be a close ratio box and bolt up to the M30 bell housing but you will have to check measurements out yourself as this is not a very common gearbox.
Thank you. When I first posted I didn't have a photo or any other info other than a verbal - "Toploader" - Google didn't even pick up Toplader vs toploader. I was trying to figure out how a Ford gearbox ended up in a BMW! A guy on Facebook reckons its out of a 2800CS - apparently they were available between 68-71 and often used in race applications. The linkage is supposed to give a much better feel.


Here's what I found out:

Gearbox:
ZF S4-18/3

Gear ratios (overall):

I 3.85 (13.28)

II 2.08 (7.18)

III. 1.375 (4.74)

IV. 1 (3.45)

Final drive ratio std: 3.45


Another box I am looking at is a Getrag 265 (Non dogleg)


I 3.82

II 2.20

III. 1.398

IV. 1

V. 0.813

Final drive ratio std: 3.45



Cleary I'm not an expert so would value any info/opinions.
1980 JPS635csi Group C Tribute
1986 635csi 5speed Alpine White M-Tech Aust Del
2001 325ci Auto Orient Blue

Previous
1988 635csi Auto Zinnerbot
1988 320i Convertible
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