Ma Chocolate Gear Boxes

[TT205 42]

Knowing zero about things like tensile strengths etc and very little about case hardening, tempering etc

 

I just wondered out of curiosity since so many people complain about the MA internals being weak - is it actually possible to disassemble and in some way harden/treat the components or is the metal they are made of simply a poor (or at least borderline) grade?

[welshpug 1,661]

Its often the casings as much as the internals that's at fault, as well as how the diff has its crown wheel fitted.

 

<< that car went through 4 gearboxes before getting converted to a BE4 box.

 

The failures I know the details of were a cracked casing, one crown wheel that came away from the diff after being fitted by Quaife (I think this cracked the diff casing too), and a stripped Peugeot sport pinion.

 

That was all on a Group N VTS engine, so effectively stock and roughly 130-140 bhp, Dunlop or Michelin rally tyres.

 

 

seems very hit and miss though, I know NickC has been running 200 bhp through his MA box in a race car around Coombe, though I do know he does take it easy on the box in the lower gears, Dave Kift I believe has killed a few Synchros.

 

 

I do remember someone on the 306gti6 forum finding what the manufacturers stated torque limits for the MA, BE and ML boxes were, I think the MA was only around the 120 lbft mark, the BE in the mid 200's, ML i dont remember but was much higher again.

 

Obviously snatch loads like you get from changes in surface/grip or bouncing over kerbs can easily pop a box.

Edited March 3, 2010 by welshpug

[RossD 44]

Torque ratings for the PSA boxes are (Source: PSA)

 

MA is 160NM (118lb/ft), "Every 19 seconds, Metz Borny knocks out an MA five-speed gearbox - 160 N.m/118 lb ft maximum torque capacity - and has produced 19 million since 1986. "

 

BE is 255NM (188 Lb/ft) and ML is 350NM.

 

"A six-speed version of the MLC with an improved lubrication system came out last June. MLC torque capacity is between 249 N.m/184 lb ft and 350 N.m/258 lb ft, and changes to heat treatment of its parts are projected to increase the maximum to 370 N.m/273 lb ft."

 

Now weather this is sustained torque, shock loadings or whatever is unclear, but it is what PSA reckon is the maximum that each gearbox can take. If you look at torque outputs of the various engines, you'll see this fits in quite nicely to which box is fitted to which engine.

 

Link to Peugeot site

Edited March 3, 2010 by RossD

[welshpug 1,661]

that's the badger!

[TT205 42]

"A six-speed version of the MLC with an improved lubrication system came out last June. MLC torque capacity is between 249 N.m/184 lb ft and 350 N.m/258 lb ft, and changes to heat treatment of its parts are projected to increase the maximum to 370 N.m/273 lb ft."

 

So would heat treatment of the original parts give a benefit where lets say BHP/Torque is increased by say 20-25%?

[Rippthrough 98]

I've had my shafts made out of EN36 and treated as I found a little wear on those on my old box, I've had the gearset itself boron-nitride coated to try and help a little with wear and tear, and fitted slightly oversized bearings in the case to help a little with rigidity - problem is, unless you have easy access to the kit to do it, that alone would put the cost above that of just swapping to a BE.

I've pinned the crownwheel on the diff. and treated that to boron nitriding too, I also spent quite a lot time fitting an extra pair of spider gears to the casing, as I've seen a couple of 106's tear the teeth off them before, so wanted to spread the load.

 

Unfortunately there wasn't really much I could do cheaply with the syncro's bar make sure they were either new or in good condition and let them wear as normal, to be honest, with decent oil in there they should do for the lifetime of the shell this time around. The coatings are pretty thin so I don't expect them to last too long, but they should help a with wear for little outlay.

Edited March 5, 2010 by Rippthrough

[TT205 42]

Interesting

 

If you wanted to provide this as a service I could probably point quite a few people (who can't use BE3 or 4 box) your way

[Tom Fenton 1,542]

BE is 255NM (188 Lb/ft)

 

 

Oh poo. Well that confirms what I have been wondering, that my gearbox is probably on borrowed time. Oh well....!

[badj 0]

As far as the hardening process that is used within the fabrication of the gearboxes, there are different types - mainly it is a process which is done before the end of manufacturing. i.e. before the molten material has cooled. Its mainly to do with the speed at which certain metals are cooled, and can be manipulated. It wouldn't quite work to get a part which is a fair few years old and try it.

Case hardening involves adding a layer of material onto the original part, so you'd have to bear in mind that the part would increase, perhaps only marginally, in dimensions.

 

Main issue i'd have with this, based on having worked on gearbox internals, is that the tolerances within a gearbox are seemingly minute to start with - I'd have thought case hardening would not be possible because of this.

 

Could be wrong but that's my 10p's worth

[Rippthrough 98]

Interesting

 

If you wanted to provide this as a service I could probably point quite a few people (who can't use BE3 or 4 box) your way

 

It's too much labour to be worth it to be honest, you know what it's like, when it's your hobby you can do it evenings and weekends, but making a wage out of it wouldn't work!

 

 

P.S. - Case hardening is where you introduce carbon or nitrides, etc, into the surface of the existing steel, which take up intersticial space and harden the structure near the surface, not adding another layer.

Edited March 6, 2010 by Rippthrough

[badj 0]

P.S. - Case hardening is where you introduce carbon or nitrides, etc, into the surface of the existing steel, which take up intersticial space and harden the structure near the surface, not adding another layer.

 

ok no problem, done a module on metallurgy which covered the phases of metal, forging, dies, castings, etc - but only brushed the surface of case hardening and other post manufacturing methods. Know a little bit more now though