[waz0]

can anyone tell me wot the difference is between an frp box and the standard 1.7 gearbox. ?

[Shilly]

gear ratios and some have a lsd

[PG12]

shot peened 1st/2nd gears to handle increased torque

[FlashBastd]

IIRC gear ratios are the same as the standard 1.7, but the final drive is actually from the 1.6, which is a bit shorter. This compensates for the larger wheel & tyre combination.

Plus as mentioned above, shot peened first & second to make them stronger, and the option of an LSD.

[waz0]

thanks for the info guys

[m_kitty]

isn't it the final drive from a 1.4, otherwise it's a stock box.

all shot peening does is work harden the gear, the same effect is accomplished by running in so it's stronger when new but no stronger than a used set of gears.

[volcomstone411]

shot peening smoothes out the metal indentation on the surface caused by manafacturing. When they are smooth it doesnt allow heirline cracks to appear.

[PG12]

m_kitty, on 24 December 2009 - 06:31 AM, said:

all shot peening does is work harden the gear, the same effect is accomplished by running in so it's stronger when new but no stronger than a used set of gears.

wouldn't this only affect the surfaces that came in contact with one another

the rest of the gear surface would still be vulnerable to hairline cracking

[m_kitty]

the only reason Ford did an extra operation on the gears was because something in the new vehicle was percieved to be likely to fail inside the warrenty period (that they couldn't put down to driver excesses). the extra power and grip are the only significant differences. if the problem was basically the gear being too weak they would have had to make the gears bigger or change the material they are made from, no amount of surface treatment will hide the lack of basic strength. if the issue was fatigue breakage (crack propogation from stress raisers on the surface) we would all be experiencing repeat failures as would the whole Ford range using the IB5 box. more power and more grip will mean the gear sees more force at the point the gears mesh, this could lead to high wear rates on surfaces that do not have the very hard wearing, perfectly matched and smooth surface caused by work hardening. indeed shot peening will produce a surface that is not predictable in it's smoothness due to the processes going on in the steel.

Volc: what you say is sort of true.the act of hitting the steel squashes the available springiness in the steel which will reduce (not remove) the micro cracks from the surface hardening process, it also mucks about with the stresses in the surface and deeper parts of the steel, as well as hardening the surface, which will actually increase the possibility of cracks starting.

PG: yes true, but the areas not affected by work hardening are generally thicker and so can accomodate cracks. the basic box was designed to work for what 100,000 miles, probably more and to operate in the worst sort of enviroment such as short cold journeys in a city, ie one with lots of stop start driving. if there was a fatigue issue it would be showing up by now as gearbox failures.

i know ford would not spend money where they didn't have to (or believed they couldn't avoid) if you bowl up at the dealer with a box full of gear teeth they are not going to cover it under warranty, you've done something silly, they can present you with the calculations showing the gear can take the forces acting on it. you turn up with a grinding sound and a box full of iron filings they can't really argue about changing it. the torque limiter fitted to regular pumas suggests they thought the box was marginal in the lower gears, the fact that it is now fitted on a wide range of vehicles and that the forums aren't littered with gearbox failure complaints, even in competition, suggests they were being very careful, possibly after the issues with sierra/escort cosworth boxes.

of course these are my opinions, someone from getrag could say it was just to get an extra £20 unit price!!