Builds The Clustertruck Rides Again - Refurbishing a 1975 Chevota (1 Viewer)

[pb4ugo]

One way to look at drive shaft angles is that optimum driveline angles are to be parallel between t/case shaft output with the pinion input. So your t/case output is maybe offset an 1"+ or - from your pinion, but they should be parallel to each other.

 

[RWBeringer4x4]

The fact that your thinking about it all means you’re probably good to go. Having the engine centered in an FJ40 isn’t too practical as it turns out. My situation isn’t exactly apples to apples with yours. I had similar issues though. Major differences in my rig: More lift (SOA), CV driveshaft in back (different angle requirements), Scout power steering box (different clearance issues).


I had my whole setup centered in the frame, ready to weld and fortunately decided to mount the PS pump to check clearance on the steering box. Fail! The pulley and box had major encroachment. Moving things to the passenger side enough to clear had me really concerned about the compound angles on the rear driveshaft at full droop. That led me to the serpentine setup, modified with the smallest pulley I could find. I got the pulley as close as I could to the box, a little too close. Later under some hard bucking on some rocks the pulley touched and peeled off one rib of the belt. I plan to shim the steering box a little to hopefully avoid that again.

Definitely not apples to apples, but even so, a very similar situation. I'd argue mounting the V8 in the center is actually MORE practical than an offset in my case, but at the end of the day, I'm considering the same two issues you had to:

1. How close is "too close" between the steering shaft and the power steering pump? Perhaps I can learn from your situation - how much space did you have between the pump and the box when you shredded the belt? Clearly, I'll need a bit more than that.

2. Can I cheat toward mounting the V8 in the center and still have appropriate driveline angles for vibration-free operation on road, and no binding at droop?

One way to look at drive shaft angles is that optimum driveline angles are to be parallel between t/case shaft output with the pinion input. So your t/case output is maybe offset an 1"+ or - from your pinion, but they should be parallel to each other.

Yep - I'm definitely OK at the rear flanges. The transfercase and rear pinion are both within 2 degrees. The issue I'm encountering is how to measure both the downward angle of the driveshaft, and well as the "side-to-side" angle. Neither are extreme, but like Cdaniel was, I'm concerned with these angles compounding under droop/flex situations.

All said though - even the angle between pinion and transfercase is pretty darn flat:

 

[pb4ugo]

what I was saying is, side to side the t/case shaft and pinion shaft are parallel. They are both going with the vehicle, going frt to back

 

[RWBeringer4x4]

what I was saying is, side to side the t/case shaft and pinion shaft are parallel. They are both going with the vehicle, going frt to back

Ah, so this goes back to drawing chalk lines are on the floor -

Plumb lines at the front and rear transfer case flanges, then plumb lines at the dif - draw two lines and see if they're parallel?

 

[pb4ugo]

Chalk lines will tell you how much it's offset. If the the engine/driveline is centered in the frame and the rear end is mounted correctly then the crank/driveline and pinion shaft have to be parallel to each other side to side. This might be why my offset side to side doesn't create a vibration. You might want to get on Tom Woods site and look at driveline angles 101 or something like that. It's a very good tutorial.

Keep in mind, your flange mounting surfaces are 90* in relation to the output and pinion shafts.

 

[Cdaniel]

1. How close is "too close" between the steering shaft and the power steering pump? Perhaps I can learn from your situation - how much space did you have between the pump and the box when you shredded the belt? Clearly, I'll need a bit more than that.

I had roughly a 1/4 inch. And I'm using GM engine mounts.

 

[RWBeringer4x4]

I had roughly a 1/4 inch. And I'm using GM engine mounts.

Are those more flexy or less flexy than the stock Toyota engine cushions I'm using?

 

[Cdaniel]

Are those more flexy or less flexy than the stock Toyota engine cushions I'm using?

I really wouldn't know how they compare. I switched to these from the AA donut style because they always collapse and crush over time.

 

[RWBeringer4x4]

Chalk lines will tell you how much it's offset. If the the engine/driveline is centered in the frame and the rear end is mounted correctly then the crank/driveline and pinion shaft have to be parallel to each other side to side. This might be why my offset side to side doesn't create a vibration. You might want to get on Tom Woods site and look at driveline angles 101 or something like that. It's a very good tutorial.

Keep in mind, your flange mounting surfaces are 90* in relation to the output and pinion shafts.

Yeah, I have read the tom woods write up - makes sense to an extent but I must just be really awful at thinking in 3 dimensions at once...

I'm not sure what the crank position has to do with driveline angles in the case - I could see in a "straight back" vehicle (centered diffs, centered tcase, etc.). Unless you are using saying use it to determine if the engine is "square" in the frame. In this case, crank/engine centerline and the transfercase output flanges are all fixed in relation to one another, with the transfercase offset intentionally to align with the differential pinions.

That being said, I can see drawing a couple of lines under the truck:

1. Drop plumb lines form both transfercase flanges and mark the ground - connect the dots on the floor to form a line (blue)
2. Drop plumb lines from both front and rear pinion - connect these dots. (Red)

These lines should be parallel if the engine is in the truck straight. This should give me the offset between pinion and transfercase flange

3. From there - I should be able to draw a diagonal line between the two plum lines, which should represent the driveshaft angle. (yellow)
4. draw lines at 90 degrees at each pinion flange, and I've built some 90 degree triangles on the garage floor which should allow we my calculate
the angle of the driveshaft (Green)

Here is my MS paint attempt to explain what I'm talking about.

If the two plumb lines end up NOT parallel, this would have to be because the engine is not mounted square in the frame - I should be able to draw a parallel line that intersects with the one that isn't, and figure out how far off it is by the same method.

Am I think about this right?

 

[Cdaniel]

You have a fundamental error in your diagram. Transfer case rear output is in line with the engine centerline, not the front output.

But your measuring plan sounds good.

 

[RWBeringer4x4]

You have a fundamental error in your diagram. Transfer case rear output is in line with the engine centerline, not the front output.

But your measuring plan sounds good.

Really??

I would have thought the engine centerline would line up with the idler shaft on the transfercase.

The front and rear flanges always seemed pretty well aligned (and offset) to me...

This begs another question - the engine centerline is essentially the crank, right?

 

[Cdaniel]

Its been too long since I was under my Cruiser apparently.

I must have Chevy on the brain

Please ignore me from now on......

 

[RWBeringer4x4]

Its been too long since I was under my Cruiser apparently.

I must have Chevy on the brain

Please ignore me from now on......

Go out into the garage, lay under your truck and think about what you've done!

Scared the hell out of me for a second - I'm already second guessing myself on this stuff, don't go telling me my transfercase should be centered on the crank!

 

[reddingcruiser]

Just to be clear, it is a straight line from from the crank shaft through the transmission output shaft, and the transfer case outputs are parallel to it. The only problem with using the differential pinions as reference is it assumes they are centered correctly. IMHO, the best way to check and compare everything is with a line from two fixed points off the centerline of the frame.

 

[Cdaniel]

Go out into the garage, lay under your truck and think about what you've done!

Scared the hell out of me for a second - I'm already second guessing myself on this stuff, don't go telling me my transfercase should be centered on the crank!

All apologies. I can't do my penance at the moment. My Cruiser is parked over a scrap pile of tubing. In my defense I haven't given it much though in a couple of years while I was busy creating another money pit from scratch

 

[pb4ugo]

You're on the right track. The driveline center line is the crank, the trans input and output shaft and then thru the t/case, to the big nut under the cone. The idler shaft is not the center line. Yes, I use the centerline of the driveline to determine if it is "square" in the frame/vehicle. Where the driveline centerline goes, the t/case outputs will follow. They will be "square" also. Your diff pinion shafts should be "square" to the vehicle if they are installed correctly. So, To avoid vibration of drive shaft U joints you want the the pinion and t/case output shafts to be parallel to each other, in your drawing and setup they are. So, by having your driveline offset to 1 side by about an inch or so, in comparison to your diffs should not be a problem.

 

[RWBeringer4x4]

You're on the right track. The driveline center line is the crank, the trans input and output shaft and then thru the t/case, to the big nut under the cone. The idler shaft is not the center line. Yes, I use the centerline of the driveline to determine if it is "square" in the frame/vehicle. Where the driveline centerline goes, the t/case outputs will follow. They will be "square" also. Your diff pinion shafts should be "square" to the vehicle if they are installed correctly. So, To avoid vibration of drive shaft U joints you want the the pinion and t/case output shafts to be parallel to each other, in your drawing and setup they are. So, by having your driveline offset to 1 side by about an inch or so, in comparison to your diffs should not be a problem.

Awesome - I'm a little slow on the uptake but I think it's starting to come together.

I'm going to go chalk up my garage (hopefully this weekend) and make some measurements. Honestly just looking at the (now way too short) driveshaft I've got stretched out across the rear driveline, I'm pretty confident I'll be able to center this and not have too much deflection. it's really a pretty straight run - not a lot of downward angle, and not a lot of deflection to the side.

The front driveshaft may be more challenging - It used to bind at full droop - I'm hoping that the longer run out front now will alleviate this, but the flanges aren't super close to parallel and the angle will definitely be steeper, so I want to avoid any compounding issues as much as possible.

 

[RWBeringer4x4]

All apologies. I can't do my penance at the moment. My Cruiser is parked over a scrap pile of tubing. In my defense I haven't given it much though in a couple of years while I was busy creating another money pit from scratch

View attachment 1444450

Very cool! That is some serious suspension...What engine did you put in it?

 

[RWBeringer4x4]

Just to be clear, it is a straight line from from the crank shaft through the transmission output shaft, and the transfer case outputs are parallel to it. The only problem with using the differential pinions as reference is it assumes they are centered correctly. IMHO, the best way to check and compare everything is with a line from two fixed points off the centerline of the frame.

I guess my thinking was - if the differentials AREN'T centered correctly, then I still need to install the engine/trans/t-case parallel to them...but adding a frame centerline chalk line isn't going to be too difficult.

 

[Cdaniel]

Very cool! That is some serious suspension...What engine did you put in it?

It’s a 2275 VW that was in my old rail I disassembled to cannibalize parts for a new chassis.

And it sucked an intake valve on the 2nd trial run for the new rail. Rebuilt and running, but I’m done with VW firecrakers.

Ecotec is in the works now.