Drive line angles.

[2JZR31]

I am fitting a 2JZ into my skyline. This will require new mounts etc and I will need to think about driveline angles. there will be a CV joint in the usual position and a big rubber dampener at the end of the trans as found on Aristos and soarers etc.

The engine sits about 20-25mm lower than the RB30 which will change the angle a bit. I should easily be able to make spacers for the CV joint X-member to compensate for this. How should I line this up? My common sense tells me that I should just aim the whole lot right at the diff and lower the CV joint to make the smallest angle possible. Is there more to it than this?

Another thing I might have to do is mount the engine slightly to the passenger side because of clearance issues. (10-15mm) I'm not worried about weight because all the heaver stuff is on the drivers side and a slight weight shift to the side is probably a good thing. I am slightly worried about possible drive line angle probs. I am thinking this small shift would be a non issue, but it appears than there may be more to it than this. My thoughts were than people routinely lower there car by 100mm and so a pissy 10mm shift to the left would be nothing compared to the drive line angle change caused by lowering. It has been suggested that moving to the side is somehow worse than going up and down. Can someone explain this in more detail?

I can see the point about needing "A second U-joint having an equal but opposite angle" but what about cars with only one uni joint like my R31? Does the CV have the same role when it comes to needing a "A second U-joint having an equal but opposite angle". And if so why can't the same thinking be applied to angling it to the side as to up and down?

Cheers.

[edo]

I'll assume its a live axle skyline. If this is the case then the diff moves up & down (& much to your distress, side to side) & angles are created the entire time. A 25mm height difference in the height of the engine over the length of the car wont make any difference. The only thing that matters is that the output shaft from the gearbox more or less lines up, I dont think Id let 25mm even bother me over the length of the tailshaft.

[2JZR31]

Cool

I am fairly confident with the drop in hight, but I was a bit worried about shifting the whole engine to the side, even if it is only 10-15mm. I think it will be GOOD for weight distribution and the move is needed becuase of clearance issues. If I realy wanted I could get it to sit exactly in the middle, but I would need to do even more stuffing around with brake boosters. If anyone can convince me that its overly dodgy, I will get it to sit in the middle. But like I said I honestly believe it will help weight distribition as all the heavy stuff is on the other side of the car, including the driver. This leaves the only concern with the drive line angle prob. Or can anyone else see another prob with this?

[Belly_up]

i think as long as the gearbox output flange and pinion input flange are parallel you should be fine. Ie, keep the engine in line with the centreline of the car. If you were to rotate it sideways instead, so that the gearbox output points *at* the diff, then you will have an uncancelled angle at the pinion end of the tailshaft, which is what you are trying to avoid. having said that, 10mm over say a 1500mm long tailshaft is only a misalignment of 0.4 degrees, i wouldn't be surprised if some factory cars were out by more than that.

[2JZR31]

Thanks.

Its good that I brought this up because originally I was going to point the trans at the diff, but thanks to Bozz's link I found out about the "uncanceled angles". Its actually better for my clearance issue move it parallel anyway.

I am now of the opinion that provided you don't screw with weight balance, this practice is no more dodgy for drive line angles as lowering your car providing you don't leave uncanceled drive line angles.

Can anyone think of another prob? Do you think an engineer would care about it?

Cheers, Dennis.

[Belly_up]

would an engineer even notice? with all the shit that hangs off an engine it's certainly wouldn't be easy to pick by eye. and as long as what i've said above was right, then i don't see that they'd mind anyway.

[hemi265turbo]

someone once said to me that a perfectly straight tailshaft is bad, I can't see why, but.. anyone?

[2JZR31]

Strange eh?

Anyhow I finished the templates for the engine mounts. The engine and box will sit 10mm to the side. I reckon it will be fine.

[Belly_up]

i think the theory with a straight shaft is that the uni joints never move through any of their range of motion, and so all the load is constantly on one point in the bearings, and thus the bearings will wear quicker. This problem will get less and less as the angles get higher, only to be replaced by the inefficiencies of the uni's transfering load at high working angles. there is probably a "sweet spot" operating angle for the uni's, but i don't know what it is offhand.

[Belly_up]

taken from here

All universal joints are designed to have a minimum of 1/2 degree of working angle. This angle is necessary in order to keep the needle bearings contained in the caps rolling. At angles less than 1/2 degree, the needles stay locked in the same position and wear into the cap, causing vibration and eventually failure.

[2JZR31]

Nice find, belly up.

[ALLMTR]

So did the offset drivetrain cause any problems?

[Pete]

I have always thought the "working angle" comments make a lot of sense where the two components are fix mounted. Like an electric motor driving a pump.

Where they are in a car the angles are constantly changing as the car move on the suspension. Even on a smooth freeway this is the case so the angle change is already happening and aiming for a straight shaft is a viable option.

Cheers , Pete.

[out_in_front]

I watched a program on the development of a 15 degree operational uni-joint, most can only operate at about 5 degrees at most.