Hi Paul and Howard, (and any others reading this).
Name here is Bruce. Sorry for the Rambo bit .. must have Sly Stalone on the mind ......
Ok on your comments. I see then that if the shafts are newly made for the application then you would think the person making them would not have put in things like the undercut on the spline at the joint. A sure weak point.
Then the pinion gear would have to be recut as well ...... not too much an issue ... Just a thought about the shafts that was all.
Yep, I know 5th hangs out the back. And there is room for all those gears in there, just a matter of machining them to suit the room available.
I hear what you're saying about the diff and wheelspin. Having 4 spider gears will effectivly halve the torque placed on them if only using 2. Interesting to note that Lotus used a 4 spider diff on all the UN1 sourced boxes from 1988.
There are also upgrades for Fords 9" diff head as well to stop such failures.
Also, using 4 spiders gives a more uniform pressure on the output shafts eg: every 90 degrees instead of 180.
More opinions!!
Which gear most loads the gearbox?? 5th! As someone explained in the thread, in the lower gears, torque is reverse multiplied so its easy to spin the wheels with excessive power, but when you're at max revs/power the wheels wont be spinning at 150+ mph! Thats when there is the most strain on the gearbox. Interesting to note, that if you have a slipping clutch for instance (worn) you can still drive ok (carefully) in the lower gears 1st, 2nd etc ... and not slip the clutch, but when you get into the higher gears 4th and 5th for instance, it will slip because there is the most resistance of the vehicle (rolling resistance, aerodynamics blah blah) and as we put our foot down the engine produces more power so it slips! I know there have been 2nd gear failures too but this has been from the dreaded input shaft flex. My 1-peice shaft is of a different material and slightly larger in diameter. But one good thing is that the shaft is supported with '3' bearings now instead of 2. By that I mean the shaft would actually flex quite well where the splined sleeve is from the clutch shaft. Now with a 1-peice shaft it has the clutch end spigot bearing to help stop flex as well. I made my shaft 25mm (1 inch) all the way from the clutch to the first bearing, so this will help eliminate 2nd gear shaft flex problems. I think the Bell shaft is wasted down along that length? .... or so it seems from photos.
Howard, I know what you mean. I uprated my Un1-13 box using ideas from the Bell upgrade. I made a 1-peice input shaft, new gears, bearing bores blah blah ... One thing I did do different to the Bell upgrade is make a new 5th gear. The shaft at that end is now 27mm up from 24 - one size all the way, no undercuts, no steps. The 5th gear size went from 18mm to 21.5mm wide - a 19% increase in size. It dont sound like much but it really is a big advance. Because there is so much stress on this gear when flat out in 5th, I have seen lots of stripped gear failures, so I decided to make new gears - also at a 0.76 ratio instead of the 0.82.
But I guess like anything, you abuse it you break it. I dont do burnouts or excessively hard starts. Once you're moving, put the boot in!
Right, enough of my opinions and theories!
