May seem like a silly question but I just want to make sure that I'm not missing something. In general the centre line of the crank through the gearbox output shaft should be horizontal at 0 Degrees. My Pinto is currently installed with the engine horizontal but it looks like the downdraft carb is offset a couple of degrees from horizontal. Is this normal or should the engine/gearbox slope down at a couple of degrees from the front to the rear of the car??
engine should slope, the carb and manifold account for it. hence why it looks off now.
Yes the inlet manifold is angle but the carb should be level.
Therefore the prop will angle slightly down to the axle and provide a slight head up angle to the engine which also provides a bit more sump clearance.
engine should tilt back, but base of carb should sit level,
So just to be sure the carb is at about 4° up at the rear with the car stood on level ground. That means that I need to drop the tail end of the gearbox until the top of the carb is level I'm asking because I've been checking thus stuff because I'm getting noise from the transmission and I think that it's because the U/J working angles.are too high at 8°. Tilting the engine back by 4° will reduce working angles which should reduce any vibration. Does that sound reasonable?
it might not fix your noise, but the engine should be tilted back to level the carb
I'm looking at the installation as it seems to be taking the output bearings out very quickly. The original 4 speed box lasted a bit longer but the 5 speed box has only lasted a few thousand miles before starting to make the same noises. I was not too bothered the first time because the box was of unknown age, but after rebuilding it with new bearings it's done exactly the same thing again
Ok, so I fabricated a new gearbox mount to drop the back of the gearbox to get the right angle at the carb flange and after a couple of test drives I'm convinced it has done the trick. In fact I'm now thinking that it was the prop that was making the noise not the gearbox, maybe wishful thinking but I'm hoping! Whereas it was evident in 3r, 4th and 5th I can now only hear it briefly under high load in 4th i.e. 1500-2000 RPM uphill. Next I'm going to try adding anti-tramp bar as the car is on leaf springs.
So thanks for the help guys
Engine should be tilted back so the gearbox output spline will have an angle to match the axle’s pinion angle. If I am not wrong the axle is 3-4 degrees above horizontal plane so the gearbox output will be below horizontal plane that many degrees. Otherwise the U/J will not be working properly and causing problems either in the gearbox or in the pinion bearings. I guess usually whichever gives up first.
Not going to disagree with any of the above but you also have to consider if the car is lowered! The axle stays in the same relative position but the engine, gearbox and front of prop all sit lower - changing prop angle. Some say a misalignment is a good thing, I tend to favour a straight line so that the UJ's just account for suspension movement - who knows what's right or whether it makes any difference at all?
Hi Katana,Originally Posted by katana
Does misalignment in your sentence mean, like I tried to describe; if the axle is pointing let’s say 3* up, the gearbox should be pointing same amount of degrees down ?
You mentioned that you tend to favor a straight line; do you mean the gearbox output facing the diff pinion flange in a 180* straight line ?
You are very right, ride height of the car changes these angles certainly and therefore it has to be re-arranged accordingly either to get the misalignment degree matching or the straight line.
But, in any case if the spring saddles on the axle is not re-welded at a different angle, the axle sits on 3-4 degrees pointing nose up, is not it correct ? ( since the front eye of the rear springs is never touched/repositioned and the lowering blocks always used under the platform )
Misalignment = engine / gearbox @ say 2 deg. down and axle @ 4 deg. up - the two UJ's will each be effectively 1 degree out of alignment. And yes, I favour a straight line gearbox - prop shaft (single not jointed) - differential. And again yes unless you want to get into rewelding the spring saddles the diff nose will always be pointing 4 deg. up - although some steel shims between saddle and spring could alter it easy enough!
What complicates matters with leaf springs is that the springs wind up as torque is applied. I have read that it's between 5 and 7 degrees for leaf springs without anti-tramp bars. With lowering blocks, and mine is lowered 2", this can only be worse. To account for this, at rest the nose would need to be pointing down by ~5-7 degrees from the line through the gearbox to account for this. That might explain what I'm seeing. Under normal load it makes no noise at all but under high load, full throttle up hill at lowish revs it makes a noise, probably because the wind up has taken the UJs away from an acceptable operating angle. So I'm going to try adding anti-tramp bars to see what difference that makes.
AT bars will certainly reduce spring wind up as that's what they are designed to do! Tyres gripping the road will try to drive the diff nose downward - AT bars fixed to top of axle tubes resist that force.
We are in line about the ultimate set up being the straight line ( perfect-inline ) will produce the lowest strain and no vibration providing that the axle can be kept in its ( aligned ) position via AT bars, 4 links etc. However, in some installations it may not be possible to create the perfect straight line then the correct equal offset should work as the 2.best set up.
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