gearbox replacement

[jamie g]

I've been advised that my m400 gearbox has too many miles on it to have it strengthened. New boxes, if you can get one, are expensive so I'm after used one from an st220. Any ideas anyone where to find one or is there another option?

[R0162]

XF do a gearbox about £1200 which gets paired to the 3.0l duratec on the Jaguars but it may not fit in the Noble,the MMT6 is a very compact unit, but surely Bernie will be able to tell you what alternatives you have that can be strenghtened? the std MMT6 is about 1900? it would probably cost the same to strengthen either box, if you find a good strong alternative that fits let us know

[andygtt]

by strengthend you mean shot peaned? the point is this stress releives new parts and as used boxs have been used they are already stress releived so its agruable if there is any point doing it.

the main 'strengthening' of the 6 speeder is the bearing (metal rather than plastic cage) and oil cooling,

[GTO600]

Jamie, if your box isn't viable for strengthening then why risk someone elses unknown gearbox !
Might be more expensive now but a bit saving long term l think.

[jamie g]

If I got my bearings replaced and the oil cooler mod how much torque could go through it safely...450?

Maybe I'll risk it and get TJ to hold the torque back.

Edited by jamie g on Friday 15th April 12:48

[jamie g]

GTO600 said:

Jamie, if your box isn't viable for strengthening then why risk someone elses unknown gearbox !
Might be more expensive now but a bit saving long term l think.

I'm guessing a lowish milage st220 box wouldn't have had too much torque going through it?

[andygtt]

I think there is probably a missunderstanding here... unless your box has been inspected and is identified as worn I suspect the gearboxman is simply saying its not worth shot peaning as its age means its already stress releived.

[TuxMan]

Jamie what sort of milage has it done ??

[jamie g]

The car has done 35k, 20k as standard and the rest after a remap.

[jamie g]

andygtt said:

I think there is probably a missunderstanding here... unless your box has been inspected and is identified as worn I suspect the gearboxman is simply saying its not worth shot peaning as its age means its already stress releived.

Gearboxman said it would be better to use a box that had an easier life and get it peaned etc. He said my gears have probably been worked quite hard. He recommended a new box but it's too expensive.

[TuxMan]

He likes to recommend a new box !!! Could try eBay , there was a dealer advertising a box on Pistonheads recently .

[mgbond]

I used a 40k used modeo box and when he upgraded it he said it was in great condition. so I would just get a used one (the correct one though as there are many).

Noble parts may have the part numbers for the 6 spd

Bondy

[5paulmv]

hi there pm me ive got a m400 box sat in garage i may sell

[BobE]

jamie g said:

andygtt said:

I think there is probably a missunderstanding here... unless your box has been inspected and is identified as worn I suspect the gearboxman is simply saying its not worth shot peaning as its age means its already stress releived.

Gearboxman said it would be better to use a box that had an easier life and get it peaned etc. He said my gears have probably been worked quite hard. He recommended a new box but it's too expensive.

The teeth on the gears fail by fatigue cracking. The surface on the gear faces, and in particular in the roots of the teeth, is placed in tension by the torque being transmitted and this can result in micro cracks at surface imperfections or stress raisers. These cracks then gradually propagate to eventually cause failure of the gear if the loading is high enough. Shot peening the gears removes stress raising imperfections but more importantly modifies the surface of the gears to give a compression layer so any cracks won`t open out and propogate for a longer time. If the gears are worn and starting to microcrack then there is much less benefit - if any - in shot peening.

[spoed]

Have the gears been checked under a lens and NDT. Cracks would show immediately with a good NDT test.

[R0162]

Bernie's none destructive testing method is looking with his eyes

[hollowpockets]

He done my M400 box with 16k on it and said it was in great condition, since had 480lbft through it and has been fine.

[daddysumo]

Why not have the gears cryo freezed. We had my old Evo box done and its taking all the abuse of a 550 bhp engine, and its not too far different in costs.Then just get the bearings uprated and add a cooler etc.