ideal axle pinion angle

[Johnny Dart]

Hi, has anyone got any idea of what pinion angle I should be aiming for, when I put my built axle in, as the spring plates are yet to be welded on.

Present pinion angle is 13 degrees unloaded, hanging on springs,
and 10 degrees part loaded, i.e. on the lift with a gearbox jack taking the weight of the rear axle leaving the rear arms of the lift clear of the chassis . Although this condition is not full weight on the axle
The Dart runs on Hotchkiss rear springs , and sits very low.
I guess it could be 7 or 8 degrees with full body weight , but its a bit tricky to measure on the ground.

[Bryan]

This might help. Miles put it up in Sinny's vibration thread.

http://www.iedls.com/asp/admin/getFile. ... =28&FN=PDF

[Matt]

Are you measuring the pinion angle relative to horizontal, or relative to the engine/trans?

Everybody always overcomplicates this.
The angle of the pinion (or the trans) on its own is irrelevant.

On a street car, you need the axle pinion shaft to be parallel to the transmission when travelling on the motorway at a constant speed. As in drawing below.

procedure:
1) put car with its weight on all four wheels. Set it onto four stacks of wood (safely) if you need to crawl under it.
2) Measure angle of engine /trans. Starter motor is handy for this.
3) Set pinion angle about 2 or 3 degrees down from this to allow for axle windup at speed. Either use tapered shims under axle, or cut and reweld perches if absolutely necessary.

Done. You can shim the axle angle (or the engine/trans) up/down after this, if vibration still present.

drag racers normally set pinion angle further down as there is more axle windup to allow for.

[RobTwin]

Nicely explained Matt

Something we still need to do on ours...