cracked gearbox casing

[buckv8]

hi folks,my dax dedion 383 has wrecked 4 gear box casings (tko 600) in 200 miles,i have checked & doubled checked,it breaks at the front where it bolts to the bell housing,no problems selection of gears tryed allsorts to fix dax or realsteel cant put their finger on it! running out of ideas,time & money! anyone heard of this before? thanks

[hairysanta]

Hi BuckV8,
do you have any vibration what ever up through the speed range

is the bell housing dailed in correctly

is the propshaft lined up

Have the prop double checked for balance

I have seen this before with out of balance props

Regards

Pete

[wilf]

What is your arrangement for engine and gearbox mounts?

Are the gearbox mounts on flexi bobbins?

If you are breaking the gearbox casing within 200 miles then somewhere there is a massive misalignment causing significant stress.

[dave]

Hi Buck?
This is a new one for me.

Is the bellhousing dialled in?
Is the bellhousing a steel one or alloy?
Have you changed the bellhousing as part of your attempts to solve the problem?
Is a spigot/pilot bearing installed?
Is it the same lug/s that break each time?

Just a thought:- If you are still using the original bellhousing and it is a pressed steel one then maybe the box mounting face of the bellhousing is distorted and when the box it bolted up tight to it this is causing stresses on the mounting face of the box.

What part of the country are you in?

[wilf]

Hmm - thinking about this one, DB gave me a clue - if the "ears" of the casing are breaking, then is the 'box seating through the bellhousing OK - or is there something stopping the front face of the gearbox from sitting up to the bellhousing - if not that would put severe bending stress on the "ears" when you bolted up the 'box to the bellhousing.

Or - is the input shaft too long and bottoming out in the flywheel pilot bearing (although I would expect clutch release problems if that were the case).

[kesha]

We saw a similar situation many years ago in some from memory Ford Capri instalations in that a vibration which was not easily detected but was caused by and I cant remember exactly whether it was the gearbox primary drive shaft or the output shaft. I remember exaning an output drive shaft and it did have a slight kick in its length. What was interesting at the time was As these were all new cars it was not a case where the Gearbox had been hung by the primary drive shaft on the engine, another instance of ears being broken off came from the incorrect selection on build of once again some Ford Gearboxes all were certyainly cast iron bell housings.
Does the above help or indicate the difficulty to remotly diagnose such. I weould first make sure that the play in the primary drive shaft is correct and that the spigot bearing coupled with primary drive shaft insertion are correct.

[kesha]

my last post was so quickly typed without proof reading first. I should have included the words "incorrect selection of the circlips in various locations in the build of the gearboxes" Many gearbox rebuilders have been found NOT to select on rebuild the specific selective circlips when these have been specified. I was lucky in my Undergraduate days to have some Ford Gearbox build practical experience but that was on Mexico and Capri etc boxes specially built for the power range of those products. Hope this helps.