So I'm mounting a rx8 rotary and 6 spd transmission in my 1976 fiat 124 and after getting them both to where I think I want them to be it looks like this:
Is this correct or optimal or what have you? First engine swap so I dont know what is right or wrong so it might not be bad. Thanks in adavance.
As long as the driveshaft angles are good, send it!
The most important part (if it's just U-joints and not a CV joint) is that the angles are equal to each other. Measure the angle of the pinion flange/yoke/shaft. If it points up 2 degrees, make sure the output shaft of the transmisssion points down 2 degrees. You also need to pay attention to the angle of the driveshaft itself. If both the angles are 2 degrees, but the trans is 10" higher than the pinion causing a large angle from the flange to the driveshaft, it's no bueno.
Disregard the numbers here because I'm rusty, but you want same angles on the trans and pinion, and no less than 1 degree and no more than 4-5 degrees deflection on the u-joint. If you don't include SOME angle, then the u-joints don't ever spin and share the load and spread around the lube.
See if this link works for some resources (some of them wrong)
You really don't want the driveshaft to angle UP to the axle, resulting in a "^" arrangement, which makes the operating angle at the axle worse under acceleration. You really want the driveshaft coming down to the axle in a V arrangement.
Try to keep both u-joints somewhere 1-3° operating angle.
In reply to NOHOME :
Tis my new favorite movie. It taught me why phase is important
Stock Fiat drivetrain used a rubber donut similar to the infamous BMW Guibo at the end of the transmission. The shaft then went back to a pinion bearing. Beyond the bearing the first U-joint angled the shaft down to the axle and it's U-joint. Maybe you could mimic something similar?
NOHOME said:
Thanks. That's a great demo video!
In reply to mad_machine :
nah i dont like guibos
manladypig said:In reply to mad_machine :
nah i dont like guibos
Nothing makes one appreciate guibos more than having to fight harmonics. Guibos nuke them. They're only useful if the differential is in a fixed location and you can get a direct line from the transmission to the differential, though.
Ford used to have two piece driveshafts with a rubber section joining the two halves for the same effect.
Knurled. said:manladypig said:In reply to mad_machine :
nah i dont like guibos
Nothing makes one appreciate guibos more than having to fight harmonics. Guibos nuke them. They're only useful if the differential is in a fixed location and you can get a direct line from the transmission to the differential, though.
That is why Fiat but the guibo between the trans and the fixed pinion bearing. The first part of the shaft was basically fixed in position and only allowed to spin. I know from experience that when the pinion bearing's rubber mount fails, that shaft makes a lot of noise and vibration as the tail section starts to move it around on acceleration.
As to Manladypig, I do not know why you do not like Guibos. The ones of my spiders all had 100K on them. The only on my BMW had 130K on it with no issues. Just have to check them for cracks every 30 to 50k
In reply to mad_machine :
i dont actually not like guibos but im just gonna be running a solid driveshaft
Does the RX7 you used a donor use a solid shaft and the Power plant frame like the Miata or did it use a guibo? I am just asking in case the trans can't take the stress of an undamped shaft
That's an RX8 drivetrain which is a solid shaft with a PPF.
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