Setting pinion and engine angles

[The Flea]

This might be a long-shot, but is anyone familiar with setting the engine tilt back angle in relation to the pinion angle. I've set the pinion before, but only after the engine was fixed into place.
C'mon, some of you 4WD and rockcrawler guys should know this.

 

[madmont]

your flanges should be parallel front and back otherwise the rotation will be uneven

 

[Toranamat69]

I am surprised no-one has answered this yet.

Anyway, the rule of thumb I have always heard - and used is the engine/gearbox should be about 3 degrees below horizontal and the diff flange should be about 3 degrees above horizontal when the car is at ride height.

You do not want the unijoints running straight - 0 degrees as they will be more prone to vibrate. You do not want excessive angle at the uni's or the unis will not last very long - especially with lots of power.

 

[gianttomato]

Whilst many people reference pinion angle to the horizontal, it is actually the difference between the crank plane and the pinion shaft plane angles.

The pinion angle you want is dependent upon the type of rear end you are running. With a leaf spring rear end you want a pinion angle of around 6-8 degrees. With a multilink rear end, a pinion angle of 1-3 degrees is desirable.

I used a magnetic roofing protractor to determine the crank plane and pinion shaft plane angles. I subtracted one from the other.

 

[Toranamat69]

Yeah my explanation was bit a bit breif & sketchy above - A diagram would be the best to describe this. Hint Hint.

I feel it is sacrilige to speak of leaf spring rear ends in a forum like this

 

[Dreamkiller]

I have a leaf sprung rear end and i think theyre highly underrated.
Especially in a drag strip point of view.

 

[thefastj]

so do i.

 

[madmont]

here are pics for you
note the alignment of the yokes end to end, very important

 

[gianttomato]

The reason why there is a slight angle introduced is that with rotation of the tailshaft and pinion, there is a natural tendency for the diff (pinion shaft) to rotate upwards under load. Leaf rear ends are looser, so they will rotate upwards more than a multilink rear end. The idea is to get the planes of the pinion shaft and crankshaft parallel under load, so a small angle is introduced to take care of that slight upwards rotation of the diff. It is important as having them out of alignment will cause vibrations and will chew out your UJs quite rapidly - resulting in the pole vaulting car if the front one lets go inadvertently.