View Full Version : M56, M59 Gearbox differences
claymore
Wednesday 5th September 2012, 18:42
Right, can someone explain to me exactly what the difference is, why can the 850r viscous coupling not be fitted to a T5?
Jamest5r
Wednesday 5th September 2012, 18:45
The shafts are thicker, thats about it i think
p fandango
Wednesday 5th September 2012, 18:46
the external casing is different on the M59, think the viscous/driveshaft locks into the casing somehow
claymore
Wednesday 5th September 2012, 18:47
Could a hybrid driveshaft be made?, and why is the M59 deemed weaker? what brakes on them?
Dangerous Dave
Wednesday 5th September 2012, 19:25
The M59 has an extra splined output shaft like the M58 AWD one does, which comes straight off the ring gear/diff case. The offside driveshaft has a viscous coupling on it which locks up when there is a difference between the two outputs from the gearbox. So its an alternative to a LSD.
Driveshaft with viscous coupling
http://i150.photobucket.com/albums/s101/bomb192uk/M59gearbox.jpg
Splined output shaft (note very worn, from my AWD)
http://i150.photobucket.com/albums/s101/bomb192uk/15092009181.jpg
Ring gear and splined shaft (again worn splines)
http://i150.photobucket.com/albums/s101/bomb192uk/15092009186.jpg
Other than that the gearboxes are the same, so I can't see why people say they're weaker TBH. The only weak point is the splines on the output shaft can wear.
Yosser
Wednesday 5th September 2012, 19:36
I *think* the diff is the perceived weak point, possibly due to extra torque loading from the viscous coupling arrangement.
claymore
Wednesday 5th September 2012, 19:37
Thanks Bomb, just the sort of reply I was hopeing for
Dangerous Dave
Wednesday 5th September 2012, 19:40
Oh and the ratios might be different (been a while since I last saw them), think pedro posted a list somewhere.
Yosser
Wednesday 5th September 2012, 19:44
I'm pretty sure the ratios are the same as the M56H. My M59 was certainly rebuilt using a gear set from an M56 (and I assume it was an H).
Dangerous Dave
Wednesday 5th September 2012, 19:48
I'm pretty sure the ratios are the same as the M56H. My M59 was certainly rebuilt using a gear set from an M56 (and I assume it was an H).
Ah yes, you're right bud, found the table.
http://i150.photobucket.com/albums/s101/bomb192uk/gearratios-1.gif
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