Is my engine/tranny straight?

[69GMC910]

How can I be certain that my engine/transmission is straight? Should the tailshaft of the transmission be dead center between the frame? I am using a POL crossmember and my tailshaft is about half an inch off center. This could be what is preventing my headers from fitting. Recommendations please!
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[donut]

Can you move the tailshaft over?

[69GMC910]

I can but it isn't easy!
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[eray92]

is it lined up with your rear end yoke?

[Truck Guy99]

If it lines up with your rear axle yoke, you got it straight. I wouldn't worry about damage if it is only a n inch. If you have aftermarket headers, compare them to your old ones. Are they thicker? Wider? Shorter? Need more info here.
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[69GMC910]

Did a small to big block swap. Changed complete drivetrain, including crossmember. I don't have a driveshaft yes as I have not completed lowering the truck. Eyeballing it from the dif though it doesn't look too bad.
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[geezer#99]

A lot of vehicles have the motor/tranny offset an inch to the pass side. Due to steering clearance and rearend pinion offset. If your rear has equal length axles the pinion will be offset. Measure them all. Centre of crank at front, tailshaft and pinion.
When you set up a drivetrain you don't need everything to be in a straight line. Your u-joints won't work like that.

[wraprail]

Originally Posted by geezer#99

A lot of vehicles have the motor/tranny offset an inch to the pass side. Due to steering clearance and rearend pinion offset. If your rear has equal length axles the pinion will be offset. Measure them all. Centre of crank at front, tailshaft and pinion.
When you set up a drivetrain you don't need everything to be in a straight line. Your u-joints won't work like that.

Um... U-joints won't work like what?

Not sure what that means but it is very important that your drivetrain is in a straight line unless you don't care it it vibrates and makes noise.
You can't just throw it together.
Use a tape measure.
If the OP is just replacing a small with a big block ( or other way around) then the motor/trans mounts and crossmember should be same. (Unless switching to a turbo 400/4L80
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[69GMC910]

I did switch to a turbo 400 from a 350. I went with an aftermarket tranny crossmember.
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[Tx Firefighter]

No, Geezer is dead right. There has to be some angle to the u joint for them to last. The rollers inside of them have to roll a bit during use. If you had a dead straight line from trans output shaft to pinion shaft, you'd be changing u joints regularly due to this.

Many cars over the years have had significantly offset engines and trans for clearance. The driveshaft going a bit sideways when viewed from above is perfectly fine.

The angles of the transmission and pinion in relation to each other should be the main consideration. That's the pinion angle that is so important to reduce vibrations.
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[Rubble]

X2 on the u joints needing some angle.I dealt with this when I worked at an IH farm equipment dealership in mid 80s.The large PTO combines always had a bit of angle on them.Also look at any highway tractor,most of their u joints have some angle too.I have ran lifted 4x4s for years and always had some angle on the u joints too,very little trouble with them too.
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[wraprail]

I agree with both posts above.
The pinion/transmission angle which combined = driveshaft angle are the most important and must be correct.
The sideways angle ( horizontal) is a concern for me.
On my own truck I have a ford 9inch which has an offset pinion. I set my driveline angles correctly but there is that sideways angle of the driveshaft. In 6th gear about 80mph and on up to 95 i have a vibration.
So my question ( and this goes to the OP origonal post) is how do you set driveline angle in the horizontal?
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Also, my linclon 9inch came factory with a cv joint at the pinion. Now has a standard single ujoint

[geezer#99]

Thanx Tx. I couldn't remember how to explain it or what the damage is called. Maybe galling or brinelling. Just knew you needed some working angle to make the u-joints work right.
Wraprail, I followed a discussion once on pinion angles and pinion offsets and how best to make it all vibration free and found this link. Lots of excellent info in here.
http://www2.dana.com/pdf/J3311-1-DSSP.pdf