The Stovebolt Site Forums The Shop Area Driveline Engine and rear axle angle

Hi guys i'm new here but i read a longer time in the Stovebold Forums.
Is there anybody who can remember the angle from the engine and the axle (shout be the same) when he swapt to V8. So i can weld the the rear axle an Mount it only once.
Thanks Ray2

There is no " right " angle, each car or truck can be different. The correct angle is what ever creates a 3 degree or less u-joint working angle at the transmission tail shaft and rear axle pinion yoke.

Measure crankshaft / transmission angle, then measure the driveshaft tube angle, the difference should be 3 degrees or less, but not straight. The angle can be sideways or up and down, or a combination of both. Next measure the driveshaft tube then the pinion angle, it should be the same as the front or very close to it, again, less then three, but not straight.

The u-joint need some angle for the rollers inside each cap to work. Three is a good easy number and not hard to get. You may or may not know this, but u-joints speed up and slow down the rotation of a shaft as they turn. As long as both angles are to same, the speed difference is canceled out and you get a smooth rotation. Get one off more then the other, and you can get harmonic vibration.

Before doing any welding, the total weight of the truck should be on the frame, or the frame should be at drive height. The pinion angle will change as you load the springs down. This also true for the front springs, the frame needs to be setting at finished level. You can do as I did and use straps to pull the frame down to the axle, I was just estimating, but got pretty close to final height.

Get yourself one of those cheap angle finders, I bought mine from Speedway Motors,

http://www.speedwaymotors.com/DECO-Angle-Finder-Tool-414-Inch-Diameter,2916.html?utm_source=bingcse&utm_medium=cpc&UTM_Campaign=CSEBing&CAWELAID=530009170000024473

They work really good for this job.

Joe

Thanks for the Perfect answer Joe

Just FYI. The stock 235 in my 54 was at a 5 degree angle in the chassis.

I know, most opt for a 3-4 degree angle.

I am trying to understand what you mean by "5 degree angle"?
What angle is your engine set at?
What angle is your pinion set at?
Carl

Joe X 2. Carb should be level, Measure angle of tranny tail shaft. Match pinion shaft to it as close as possible. Hopefully, as said, 3-4 deg. Weld perches to accommodate. Diff will rotate upwards upon acceleration. Rule 1. Tail shaft and pinion shaft must be parallel.

The pinion and tail shaft do not need to be parallel, they do need the same u-joint working angle. If the tail shaft is pointing down, and driveshaft is level, pinion can be up or down, as long as the working angle is the same. Next time you are around a long wheel base box truck, notice the driveline and how each driveshaft section is at a different angle.

Most race cars start with pinion angle lower and a steeper working angle, so under a hard launch ( load ) when the pinion tries to climb up the ring gear, the u-joint angle is still with in its range of operation.

Carburetors also do not need to be level as most engines are pointing nose down once all the weight is on the chassis. Get close and you will be fine, its not the end of the world if its angled.

Joe

We are not talking about race cars or two shaft. Geometry tells us that if two parallel lines are intersected by a transversal, it creates congruent angles. That means the Ujoints will be operating at the same angle. If the two are not parallel, they will not. The angles should be equal and opposite for a normal truck with leaf springs. There can be some tolerance here, as in: 1/2 deg. Ujoints are designed for 1-3 deg angle.
The differential windup will tend to straighten out the working angle, that's OK. Zero angle is not recommended because this does not "cycle" the ujoint enough to lube the needle bearings.

A motor should indeed be set up with the carb mounting at level. Not close, but level. You don't screw around and set the "float level" and "float drop" precisely and then set carb at an angle. It is known that most Chevy motors have a tilted intake/carb mounting surface relative to crank shaft centerline. Set carb mounting level and the tailshaft will be tilted down 3 or 4 deg(probably 4).
This subject always creates big disagreements because people start talking about drag racing, circle track, wind up, suspension type and the many website discussions. I am sticking with the basics.
It's not rocket science but it is important to avoid ujoint failure, vibration and fuel delivery problems. With several "angles" to set up, close is not good enough. Errors will compound. My first boss would always ask "If it's not right, what is it?" I would have to answer.... "wrong".

BTW: Motors do not sit nose down in my experience. Joe's first post has great info, his second post is what I'm discussing. Where is the first Joe?

http://www.roddingroundtable.com/tech/articles/driveline.html

This is where I got the information from. I also read a lot over on the H.A.M.B. site. Those that seemed to build a lot of cars and chassis agreed that as long as the angles equal each other and yokes were in phase, the shaft will rotate smoothly. Is it ideal to have one point up and the other down, not really, but in some cases, it's the only way.

I brought up race cars and accelerated launches, because not knowing how this truck will be operated, I thought it might be interesting to the owner. A heavy load can change the pinion angle just as much as drag racing does so if he was planning on really working the truck, an extra degree at the pinion might not hurt. Is it needed, probably not, but information is free and doesn't hurt to have.

I know the 250 in my truck is slightly nose down, it was level when I set up the chassis in 2000, but I have since lowered the front and added bigger rear tires and have found no problem with setting or tuning carburetors. I suspect 99% are set level, but there is always the 1% that are not and still work ok. Getting close is all you can do unless the whole weight of the finished truck is setting on the springs. You can't assume the frame will be level, so unless you are 100% sure about the frame angle, then the carb angle is just a guess. I doubt most gauges are true anyway, thats what I mean when I said to get it close.

It's like your quote says, "we all have our opinions", it's up to the end user to decide whats right for them.

Joe

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