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Can someone help me out with drivetrain alignment?


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Hi guys, i was wondering if someone with a JTR converted v8Z could throw a couple of measurements my way...

 

I would like to know how far it is from the driver side cylinder head base directly to the engine bay wall. same for the passenger side. I figure that these two measurements will help me make sure that i have stuff lined up...

 

or if you know of a better method... i would really appreciate any insight.

 

Pete? i know you put a whole lot of time into lining up you drivertrain...

 

I have read through alot of the posts regarding this, but havent found any real concrete numbers, aside from the distributor to firewall clearance...

 

I am getting pretty close to getting this thing going, just need to finish the fuel system, and general wiring, some tranny work, and about 35 other little things.

 

thanks for your help,

Joe

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the engine is sitting in the bay, with the transmission on a stack of 2X6 boards....

 

I have the driveshaft in place, and it certainly has too much angle.

 

I cant figure out how to move the tail end of the transmission any further towards the passenger side...

 

I may have to remove the engine/transmission again in order to modfiy the crossmember a little more.. I think that the JTR method of slotting the crossmember is very unscientific. I am surprised that i did it that way, instead of getting concrete measurements.

 

This would be much easier if i knew exactly where the M/M bolts were supposed to be on the crossmember towers.

 

I havent bolted up my tranny crossmember yet because i am waiting on a caprice tailhousing, and because i am not comfortable with the idea of just winging it on the drivetrain alignment. i plan on taking this vehicle on very long trips, and i am not about to leave something this important in the hands of fate.

 

Once i do get the alignment just right, i plan on filling in the slots on my crossmember with some small pieces of 1/4" steel.

 

I'm just getting tired of sitting underneath my car in my driveway in the 100 + degree heat with a tape measure and a pry bar...

 

yeah.. no ranting so i'll stop there...

 

Joe

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Joe,

I will check some measurements on my LT1/T56 this evening and post the measurements. My drivetrain alignment is close to perfect. I know this because I used a solid welded driveshaft to line everything up.

BTW, I slotted the mounting hole in my X-member, but only backwards to push the engine as far back as possible (possible with the LT1 because of no rear distributor).

Tim

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There isn't any concrete numbers. If you have an HEI dizzy, move the engine back enough that you can still move it, maybe 1/2 to 3/4" from firewall. If you have the small cap dizzy, you have more room to go back. If you have a stick tranny, make sure the shifter comes out of the stock hole with enough room to go through all the gears. If you have an auto tranny, it can go anywhere in the tunnel. As for the tail end of the tranny, just make sure it's centered in the tunnel.

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As for the tail end of the tranny, just make sure it's centered in the tunnel.

 

Mike,

My shaft is offset to the pass. side a bit. Maybe because of the R230, but I thought that the R200 was also slightly offset?

 

Tim

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the R200 is also offset to the passenger side.

 

You need to figure out what the diff's relation is to the unibody, then how to translate that to work with the engine/transmission.

 

the problem i have had is finding good measure line. spots that are constant like the frame rails... but they are not directly lined up with the diff. so i need to find the anglular relation between the frame rails and the differential so that i can set up the engine/transmission in direct relation to the fram rails/diff.

 

Also...space constraints due to the large automatic tranny makes life very difficult...

Joe

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mike.. you just posted information that directly disproves what you said.

 

 

you need to try to make the driveline angles small. therefore the engine/tranny should be offset in relation to the differential.

 

the diff is set, it has it's position that is required to keep the halfshafts from breaking(sorta). you may not want to point the tranny at the offset, but it should be offset to minimize driveshaft angles.

 

I'll go draw a picture...

 

Joe,

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where are our resident engineers?

 

somebody has to have real numbers for thier drivetrain alignment...

 

If i could set up a laser pointer 90* from the diff flange, i bet that the dot would appear at the driver's side of the tranny tunnel, near the engine bay. I wish i had sureveyor's tools :-)

 

 

thanks,

Joe

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mike.. you just posted information that directly disproves what you said.

 

 

you need to try to make the driveline angles small. therefore the engine/tranny should be offset in relation to the differential.

 

the diff is set' date=' it has it's position that is required to keep the halfshafts from breaking(sorta). you may not want to point the tranny at the offset, but it should be offset to minimize driveshaft angles.

 

I'll go draw a picture...

 

Joe,[/quote']

 

I'm talking about the bottom part of this picture. The engine/tranny is centured, but the top pic shows the tranny pointing down sligtly to reduce the angle.

 

ap2.jpeg

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I'll take some numbers down tonight.

 

But don't sweat the side to side crank/tranny-output shaft to diff-pionion centerline offset too much. The JTR mounts move the engine over about 3/4", if you use the stock holes in in the crossmember towers (slot them in the for-aft direction to be able to move teh engine for/aft).

 

Try to get the engine and trans positioned so they point forward, not at an angle left to right (no "yaw", so to speak). The R200 pinion should be pointing forward too. That way the shafts are parallel in the horizontal plane - important. Yes, they will be offset a bit, but in my car the u-joint angles in the horizontal plain were less than 1 degree - very acceptable.

 

The real problem is:

1 - getting the up/down attitude (pitch) of the engine/trans to be the same as the pinion (measure with an angle finder laying up against the pinion flange on the R200. Do this by:

(A) Playing with the tranny mount height,

(B) Not using the JTR-speced 1/2" thick spacers between the frame rails and the engine crossmember,

© raising the rear of the diff (remove or cut down the Mustache bar top isolators), and/or

(D) Lowering the front of the diff (the Ron Tyler designed front diff mount

is GREAT for doing this.

 

I did ALL of the above to get my vertical plane u-joint angles to be less than 1 degree.

 

In my car the total u-joint angles (due to vertical and horizontal plane angles being added by TOTAL-ANGLE = SQRT(HORIZ_ANGLE^2 + VERT_ANGLE^2) are about 1 degree, and the same. I have NO vibration under heavy acceleration, but MANY V8 Z's do, especially the JTR conversions.

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As I said, my driveline is almost perfectly in line in all planes. I am assuming that once the bushings/mounts settle (compress) a bit and the entire drive train settles after a few miles, it may end up being out by a degree or two, but I think that is the best I will ever be able to get things.

 

Tim

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well... to me my horizontal plane looks wrong. vertical shouldnt be too much of a problem though, because that is easier for me to modify... as it is now it seems like i may not be able to get the horizontal lined up easily.

 

then again, i've never done this type of stuff before... after i get this V8Z done, everything i do is going to be easy in comparison...

 

Pete: i guess i will have to make an angle finder... or buy one....I look forward to seeing the measurements you have though.

 

thanks again,

 

Joe

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That method I gave of finding the total angle is TOTALLY HOSED

 

What you need to do is measure both angles, take the Cosine of each, multiply the cosines together, and take the arc-Cosine of that result to find the total angle:

Cos(Total_angle) = Cos(horizontal_angle) * Cos(vertical_angle)

or

Total_angle = ArcCos[ Cos(horizontal_angle) * Cos(vertical_angle) ]

 

If it turns out you have 1 degree of u-joint angle in the horizontal plane, and 1 degree in the vertical plane, the total u-joint angle is 1.414 degrees.

 

My math and engineering teachers would kill me if they saw the previous method! Too much time in meetings and doing program management and not enough technical work - my mind is turning to mush!

 

Anyway,...

 

I'm wondering, did you put the taller JTR engine mount spacers on the driver's (left) side? That's the way it should be. If you had them switched, the engine would be shifted over to the left side of the car, and the horizontal u-joint angle would be large.

 

The best way to measure whether things are lining up with a good for/aft direction is to find the center point between the inner control arm pivots, at the front and rear of the car. Tie a stiff wire around the bolts or something that stretches from one pivot bolt to the one on the other side of the car, and mark the halfway point on the wire. Do the same at the other end of the car. Now you can tie a string between these midpoints and use that as your reference for/aft line for the chassis.

 

Here are a few cheap angle finders (for the vertical angles anyway):

http://roofgenius.com/roofangle.htm

http://www.toolking.com/shop/view.asp?ID=2225 $5!!!

 

This one is pricey, but can measure the horizontal angles as well:

http://tools.cheap-internet-store.com/PID0000000a00004c64786a647062397351/Bosch_DWM40L_Miter_Finder_Digital_Protractor_Angle_Finder/

 

Or just measure the rise and run of the triangle you're measuring the angle of, and use trig (Angle = arctan(rise/run)) :)

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where are our resident engineers?

 

I sometimes play one at meetings here at work :)

 

somebody has to have real numbers for thier drivetrain alignment...

 

If i could set up a laser pointer 90* from the diff flange, i bet that the dot would appear at the driver's side of the tranny tunnel, near the engine bay. I wish i had sureveyor's tools :-)

 

Oh, I see. It sounds like the mounting of your Diff is really messed up.

 

Another trick is to use a carpenter's square and lay it on the diff pinion flange. The long part of the square will help visualize the angle the pinion CL makes with the car. You can use this to help measure the rise/run as well.

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Pete, i misspoke,

 

when i was under the car a few minutes ago i realized that the diff is offset to the passenger side, with very little horizontal angle, the vertical angle on the diff is not aligned with the crossmember, it seems to be in a slightly "nose up " position, so i guess i will have to go and remove the top washers for my mustache bar.

 

my motor mounts are correct.... and i dont think that you can mess up very badly with the diff install... at least not with that big old bar stuck to the back of it!

 

Thanks,

Joe

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Note that my Z has had it's frame rails replaced. They might not be exactly in the same place as stock - but I bet they're within 1/8" left/right at the firewall - where I made these measurements:

 

Right side of engine block, back outer corner of block deck: 3-3/8" from vertical line running up from the inside vertical side of the frame rail.

 

Left side of engine block, back outer corner of block deck: 4-1/2" from vertical line running up from the inside vertical side of the frame rail.

 

O.k. So your diff is pointed forward, parallel to the for/aft direction of the car (by eyeball).

 

And the diff is nose-up - pinion flange is tilted so that the top of it is further rearward than the lower edge. That sounds correct.

 

With the low height that the JTR mounts locate the engine on the crossmember, adding the 1/2" spacers between the crossmember and the frame rails just lowers the engine even more - to gain more clearance above the distributor, under the JTR hood latch/bracket. I don't think this is needed - I've never heard anyone that has tried NOT using those spacers having too little vertical room for the distributor or the top of the transmission. I say, leave them out and try it that way first. Lowering the front of the engine/trans with those spacers installed only makes the crank/transmission tailshaft centerline even closer to level, and farther away from the more severe nose-up attitude of the pinion centerline - making the u-joint angles less similar (BAD THING).

 

With the R200 mounted as stock it's nose-up by several degrees.

With the engine trans installed with the 1/2" spacers between the frame rails and crossmember, and the JTR tranny mount, the engine crank/tranny tailshaft angle is around 1 degree nose-up from level.

 

Since you need to get them close (within a degree is good) to the same nose-up angle to make the (vertical) u-joint angles nearly the same.

 

The problem with raising the rear of the diff to adjust the nose-up angle of the diff/pinion CL to be more level is that the front of the pinion (the flange) is a good bit higher than the back of the tailshaft of the trans. This leads to large u-joint angles. Raising the rear of the diff helps keep the halfshaft u-joint or CV joint angles small under squat, and does help the rear u-joint angle approach the value of the front u-joint angle.

 

That's why I like the Ron Tyler front diff mount. It lowers the front of the diff so that the diff is almost touching the top of the front tranny crossmember, instead of being an inch or more above it, when you have the stock diff mount in place. Lowering the front of the diff helps get the CL of the diff closer to the CL of the tranny (if you extend them and measure between them perpendicularly). That helps lower the u-joint angles. And low value, equal u-joint angles is what provides for less stress on them and less vibration under heavy acceleration.

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