Thanks for all the input about how I didn’t solve a problem with a solution that worked for me. I’ll continue to build in the future with the drive train aligned. Please feel free to design/build in your own way. My apologies to the O/P for his thread getting highjacked.
Pinion and trans angles need to cancel each other, so if your engine is located straight then offset at the rear axle doesn't change the driveline angle at pinion and trans. If it's 1" or 3" offset, the angles still cancel each other. It's not the same as having the pinion angle up or down and not matching the angle at the trans. Now if you thought maybe you'd angle the engine so the tailshaft of the trans pointed at the end of the pinion, then you'd induce vibration for sure!
This is why I no longer provide explanations when people are wrong. They never accept it, and correct their thinking. They simply double-down. Current events prove that this behavior pattern is common, widespread, and dangerously harmful.
I've brought this subject up in the past, but since no one else has so far on this post, thought it might be helpful..... Years ago I set up the 9" in my '40 with a centered carrier, offsetting the pinion 15/16". I was curious about how a "top view" drive shaft angle would affect the normal "side view" drive line angles, so I checked with a company that makes U-joints, and found the info I was looking for on a Dana ****er PDF I saved. file:///C:/Users/Owner/Do***ents/****er%20U%20joint%20info.pdf True U-joint angles have to be calculated when there are both top and side view, or compound, angles. In my case the "top" view angles were less than 1 degree, and was added to the "side" view 1 degree angles for a total of about 2 total or true degrees. I wanted to stay under 3 degrees for U-joint longevity. In your case, I would be concerned if your pinion offset is really 3", but don't think offsetting the engine would be necessary. Really depends on what U-joint angles you are comfortable with. Copy and paste the above link and it should open. Scroll down and you'll find the info.
Given the motor/trans in the short wheel base Dodge truck ch***is (with the very short front sheetmetal clip), I suspect the angles for the U joints were probably beyond their operating capacity. Probably because the trans center line and the pinion were not parallel in the up and down position. The 429 Ford oil pan does not fit in the Dodge truck ch***is with that short front sheetmetal. (the front crossmember and the oil pan want the same space, the short front sheet metal compounds the issue) without the front of the motor being raised up too high to get it parallel with the pinion center line, unless the rear axle is rotated beyond the U joint capacity. The double cardigan u joint probably solved the severe angle issue caused by the motor/trans to pinion not being parallel. I've built Mopar hot rods for 50 years (my current Mopar is a 49 Dodge pickup), offset side to side and up and down rear ends and motor/transmissions are standard procedures. Driveshaft U joint failure has been pretty rare.
Yuppers because the fool has never looked under a 57 ot later F 100 through a mid 80's F150 or he would see that almost every one of them had a 9 inch with the offset pinion and driveshaft doing both angles and no U joint issues and I have never seen one word on stock height pickups with nine inch rears having any more U joint issue than any other vehicles. Those clowns always get their pink ******* wadded up in a knot because it "doesn't look pretty" with the driveshaft at a slight angle but it is all about looks to them and not actual mechanical issues.
After more consideration, I thought some other source might know about the geometry of all this. The term for it is “compound angles” and AI seems like it has a good answer. For the people who said “no problem”, it is no problem as long as total amount of the two angles doesn’t exceed the design limit. Makes sense to me. The situation I described was probably the worst of possible situations with a lot of shaft angle in two directions and low gearing at highway speed. The AI version: 5. Practical limits (rule-of-thumb) For single Cardan joints: Ideal continuous operating angle: ≤ 3° Acceptable with care: up to ~5° Compound angles should be treated as one larger angle, not two small ones Example: 3° vertical + 3° horizontal = 4.2° resultant → already near the upper comfort limit for continuous duty 6. When damage will occur Undue damage becomes likely when: Resultant angles exceed limits Front and rear joints have different resultant angles Axes are not parallel in 3-D Shaft speed is high Suspension travel causes angle mismatch under load In those cases, symptoms include: Cyclic vibration (2× shaft speed) Heat in the joint caps Rapid brinelling of bearings Seal failure and grease loss 7. When to use a different solution If you must run compound angles: Use a double-Cardan (CV) joint at one end Or introduce a center bearing Or realign drivetrain to reduce resultant angle Bottom line ✔ Two working angles in different planes do not automatically cause damage ❌ But they increase sensitivity, load, and wear ✔ Equal and opposite resultant angles in 3-D still cancel velocity error
Hello, If you want a simple solution, find a complete rear end that fits your driveline and motor in a straight line.. No motor should be offset as you will also have to move the trans mount or at least modify it. Just to get a correct angle. The majority of folks have not moved the motor and trans to accommodate an offset rear end. When we built our 40 Willys Coupe, we had an SBC motor and LaSalle transmission all put together with the appropriate mounts. So, the next step was to find a complete rear end. We were used to working with Chevy rear ends, so we got a 56 Chevy complete rear end with springs and positraction gears. With all of the measuring, the Chevy rear end fit right in line with the motor and transmission. Now, all we had to do was to get our driveshaft made and we were ready. The motor was installed using mounts for the SBC to the new equal mounts on the frame. Everything was centered and moved back the allowed 10 percent for our Gas Coupe/Sedan rule allowance. simplicity in motion, it fit perfectly and all in a straight line. When the new driveshaft arrived, it hooked up easily… not offset and no problems with the rear axle we welded and attached in place. Jnaki Everyone has their own way to install whatever in hot rods, but a simple thing is straight line install and less pressure on the off angles in the driveline. But, as usual, you may do what ever you want, since it is your build. And your friend’s idea that creates more work for you. Sell the old off set rear end and get one that fits straight without any weird angles or pressure points for the future. YRMV
That is excellent info all on the one page, although all of it has been covered at some point earlier in this thread. Truth is that when compound angles are introduced it can get hard to visualize and understand.
Last year I put a car back on the road after a 30+ year snooze. Learned a mess of lessons even at an advanced age. It's a boatload more work than you think - and if you mod 1 thing, it affects a ****load of other things. KISS. Don't make unnecessary mods. Don't overthink things. These simple lessons will save you a quadrillion headaches and a ****load of work. From a practical approach, keep the motor trans close to centered. Don't sweat the offset pinion.
Keep your friend away from any fabrication, and don't take his advice. I'm curious why you think a u-joint can only operate effectively on a single plane. The statement above is very much incorrect. The u-joint will combine the vertical and horizontal angle into one angle and work with that on both ends. It's not rocket surgery.
So from the comments and information at this time I plan on leveling the rear end and leveling the trans (not on the same plane)…..and not offsetting the motor ,so I will have an angle (offset) of 3” from the trans over to the rear end of 3” and the angle down from the level trans to the level rear end. Thanks!
The trans output shaft and pinion shaft are not normally run "level". They are usually both installed sloping downwards towards the rear at around 3 degrees. Best to keep them both at the same angle off horizontal to eliminate vibration.
One note is if you have leaf springs... you need to compensate for spring wrap on hard acceleration. My engine is at 3.2 degrees down and the pinion is at 2.7 degrees. That gives me a half degree for spring wrap, which works well for me. I like Good Vibrations but not in my drive line!
Nothing wrong with a level engine. The manufacturers started dropping em down at the trans for clearance. Lots of older cars had em level. Only affects the carb angle/fuel bowl. Plenty of simple cures for that. Front wheel drive cars could care less about that and the roads are full of em. Ive had drive shafts dang near zero. No issues. Building stupid low stuff you sometimes raise things up Pinions above the trans output. No issues.
Rules have exceptions. In this case the output and input are still offset. Just from above vs from the side. U joint’s will still be doing the flexibility thing.
Most cars I’ve owned (Fords) have the engine sloped down a bit. The factory intake manifolds carb pad is purposely machined at an angle to compensate for this, so the floats stay level.
Yep Many were built level. Lots of boat intakes are level at the carb I’ve got straight 6 intakes with no angle on the.carb mounting. Intakes can be milled to correct the angle if not needed or a wedge spacer.
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