pinion angle help after lowering (W/drawing)

[AustinScott]

hey guys, looking for some advice on correcting my current mismatch pinion angle

Below are the current angles at ride height



I'm thinking I should shim up the tranny at the mount, but not sure if this is the best idea.... looking for input on where I should start shimming, rear end or tranny... and by how much..

thanks for any and all help!

Scott

[kaycee]

Do a search here there is a coupla post on this,if I remember right your trans and rear should be within 3* of each.Why does your trans dip down so much seems like that would cause oiling issues with motor and trans

[fleetsidelarry]

Hey Scott, nice drawing, visuals are very helpful.

can you clarify what appears to be a discrepancy between the value of the angles and the drawing? you note the engine/tranny angle as "negative", the front driveshaft as "positive", the rear driveshaft as negative, and the pinion angle as positive BUT all seem, from the drawing, to slope down from front to rear. if you define the engine/tranny angle as "negative", then, according to the drawing, all the angles are negative. it matters when calculating u-joint angles. for instance, are you saying the front u-joint angle is -6° + 1° (5°), or -6° + -1° (7°)? sorry if that's confusing

other than that, my understanding is, for 2-piece driveshafts, the pinion angle should be the same as the front driveshaft. for 1-piece shafts the pinion angle should be the same as the engine/tranny. u-joints should have some angle. I don't think it would hurt to raise the rear of the tranny some, provided all the angles stay within tolerances.

I have a great link to a Spicer PDF file but can't seem to get it to post, sorry

according to the Spicer manual, u-joint angles should be 1-1.5°, not more than 3°

[brad_man_72]

Duuuuude your driveshaft is REALLY bent.
Shim the back of the trans up. Poly trans mount raised the rear of my trans quite a bit, so that may be a good starting point.
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[AustinScott]

Originally Posted by fleetsidelarry

Hey Scott, nice drawing, visuals are very helpful.

can you clarify what appears to be a discrepancy between the value of the angles and the drawing? you note the engine/tranny angle as "negative", the front driveshaft as "positive", the rear driveshaft as negative, and the pinion angle as positive BUT all seem, from the drawing, to slope down from front to rear. if you define the engine/tranny angle as "negative", then, according to the drawing, all the angles are negative. it matters when calculating u-joint angles. for instance, are you saying the front u-joint angle is -6° + 1° (5°), or -6° + -1° (7°)? sorry if that's confusing

other than that, my understanding is, for 2-piece driveshafts, the pinion angle should be the same as the front driveshaft. for 1-piece shafts the pinion angle should be the same as the engine/tranny. u-joints should have some angle. I don't think it would hurt to raise the rear of the tranny some, provided all the angles stay within tolerances.

I have a great link to a Spicer PDF file but can't seem to get it to post, sorry

according to the Spicer manual, u-joint angles should be 1-1.5°, not more than 3°

I had a feeling my brain was thinking about this in the wrong way, that is why I made the drawing.
I was trying to think about each angle in relation to the pivot point not to each other
Front U-joint example: My brain says at the u-joint the transmission is hitting it at a downward angle so it must be (negative) and the drive shaft is hitting it at an upward angle so it must be positive

But if I'm understanding you correctly I must define the angle of each involved as a whole & not just at each connecting point?

so, the the drawing is correct but the values are not.
This is what I measured

Trans output shaft 6° (higher towards the front of the truck)
drive shaft 1° (higher towards the front of the truck)
rear end yoke 3° (higher towards the front of the truck)

So if I I'm thinking about this correctly now is the below statement true?
Front u-joint 6° + 1° = (7°)
Rear u-joint 1° + 3° = (4°)

And the reason the thing vibrates at higher speeds is not because of the difference between the two, but for the fact that I have exceeded the max recommended angle in the front drive U-joint?

thanks for helping me and talking thru this with me....

Scott

[AustinScott]

Originally Posted by brad_man_72

Duuuuude your driveshaft is REALLY bent.
Shim the back of the trans up. Poly trans mount raised the rear of my trans quite a bit, so that may be a good starting point.
Posted via Mobile Device

I had a feeling that it was out of wack... Now that you mention it I do seem to have a bit of a weird issue with my trans. it seems to be sucking bubbles or just getting air some how... might be the angle... more on that to follow...

I have a poly mount already, but I didn't use the shim that came with it when I installed the mount.
The trans is a 2004R sitting on the stock th400 cross-member






sounds like I need to shim the trans up to fix that first, then re-measure everything.



When I measured the output shaft, I was measuring it on the lift in the air, so i had to do some math... can someone please check what I did and make sure I'm not totally off

I did a frame angle measurement offset between the frame rail in the air on the lift & the frame rail when the truck is sitting on the ground at ride height & I found only 1deg difference between the two.

On the ground the frame rail is -1 (higher towards the rear of the truck)


On the lift the frame rail is 0 (flat even)


SO what I did was subtract the difference from the over all output shaft measurement
Output shaft is +7 on the lift (higher towards the front of the truck)


This is how I came up with the 6 deg for the trans output shaft.


Thanks again for all the help with this, the truck runs fine, it just has some vibration at freeway speeds 70 and above

Scott

[derrickmanx1]

If you have room i'm thinking bring the rear of the trans up about an inch and re-measure. From what I understand it would be trans @-3 rear end @+3 for you. I could be screwed up but an old mech told me they should be basiclly the same angle "opposite" on a one-piece shaft. I had the same question a couple of weeks ago is why i'm answering and that was what I was told but mine is -3 trans and +5 rear end. He also told me that the trans should be negative and the rear end should be positive. There must be a difference in the shaft though, it can't be straight. I hope this makes sense.

[geezer#99]

Don't check tranny angle on the shaft. Check it on the seal.
It don't matter how level or un-level your frame is you want the centreline of the tranny equal to the centreline of the pinion.
Here's a link to a recent thread.
http://67-72chevytrucks.com/vboard/s...d.php?t=569350

[AustinScott]

Originally Posted by geezer#99

Don't check tranny angle on the shaft. Check it on the seal.
It don't matter how level or un-level your frame is you want the centreline of the tranny equal to the centreline of the pinion.
Here's a link to a recent thread.
http://67-72chevytrucks.com/vboard/s...d.php?t=569350

Great thread!, enjoyed the video it explained everything I needed to know.

Also, the reference to the frame rail was only due to the difference in measurement between the truck being on a lift held up by the frame and being on the ground held up by the suspension, this was because when I measured the trans it was on the lift, so I had to figure out how that information could be translated to the truck on the ground.

I did measure at the seal & it had the same reading as the output shaft, so I just stuck it to the shaft for the picture, this freed up my hand to take the pic

I will get the trans moved up and see what that does for me.....

thanks everyone for all the info & guidance.


Scott

[fleetsidelarry]

Originally Posted by AustinScott

Trans output shaft 6° (higher towards the front of the truck)
drive shaft 1° (higher towards the front of the truck)
rear end yoke 3° (higher towards the front of the truck)

So if I I'm thinking about this correctly now is the below statement true?
Front u-joint 6° + 1° = (7°)
Rear u-joint 1° + 3° = (4°)

Scott

Hey Scott, sounds like you've got it figured out already but because I did such a terrible job of explaining it, the above calculation is off. since everything is running at the same slope, you're looking for the difference in the two angles, so Front 6° - 1° = 5° and rear is 3° - 1° = 2°. I also thought from your drawing that you might have a 2-piece shaft but it sounds like not, so even easier.

I didn't watch the video yet so it may all be clear already, but just to elaborate on what geezer said, yes you want the centerlines (angles) equal but you don't want them to be the same line, rather you want them to be parallel.

also, I don't know if your oil leak is due to the tranny angle, it's my understanding that most engine/trans come from the factory at something like 5° (lower in the rear)

[geezer#99]

Be carefull moving the tranny up. You want to keep the carb level.

[fleetsidelarry]

Scott, just watched the video, he certainly did a better job of explaining than I did also, the post contained a link to the same spicer manual that I was trying to give you earlier but couldn't get to work

[cubber]

Good thread. I just put a 4 deg. shim on my rearend after bagging, and all was good.

[ItsRandy]

Originally Posted by AustinScott

Great thread!, enjoyed the video it explained everything I needed to know.

Also, the reference to the frame rail was only due to the difference in measurement between the truck being on a lift held up by the frame and being on the ground held up by the suspension, this was because when I measured the trans it was on the lift, so I had to figure out how that information could be translated to the truck on the ground.

I did measure at the seal & it had the same reading as the output shaft, so I just stuck it to the shaft for the picture, this freed up my hand to take the pic

I will get the trans moved up and see what that does for me.....

thanks everyone for all the info & guidance.


Scott

This may help. http://www.billavista.com/tech/PDF_I...Guidelines.pdf

With a two piece shaft you set the front shaft 2-3* down from the trans output shaft center line. Then set up the pinion angle 2-3* pointing up from the front shaft center line. As said earlier, the drive line angles don't care what the frame is doing...it's all about what the crank/trans/drive shaft(s), pinion center line are doing.

[AustinScott]

well yesterday I put the truck on the lift & started to test the idea of moving the transmission up.
It was a no go... cant move it up due to exhaust hitting the frame.... I moved it up a half an inch and it only change the angle by 1 deg. I will have to redo my exhaust if I need to move up the trans.... So I guess my next question is can I just shim my rear end +3 so it matches the trans angle & call it good?

[geezer#99]

Of course you can. That's the normal way.
Summit has some.
http://www.summitracing.com/search?k...%20shims&dds=1

[brad_man_72]

You have a high speed vibration. That's a ballance issue most of the time.
Shudder on takeoff is the big symptom of an angle problem.
Try to get the angle to be less than 3* difference between one side of the joint to the other.
When is the last time the shaft has been ballanced? Does the shaft have new ujoints? Decent quality joints like spicer or neapco or junk like precision or house brand? Something as simple as changing the joints can effect the ballance, especially if you flip the trans yoke or even flippig the driveshaft. Is your pinion yoke worn? Is your driveshaft long enough, how much of the trans yoke hangs out of the trans at ride height?
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[AustinScott]

Originally Posted by brad_man_72

You have a high speed vibration. That's a ballance issue most of the time.
Shudder on takeoff is the big symptom of an angle problem.
Try to get the angle to be less than 3* difference between one side of the joint to the other.
When is the last time the shaft has been ballanced? Does the shaft have new ujoints? Decent quality joints like spicer or neapco or junk like precision or house brand? Something as simple as changing the joints can effect the ballance, especially if you flip the trans yoke or even flippig the driveshaft. Is your pinion yoke worn? Is your driveshaft long enough, how much of the trans yoke hangs out of the trans at ride height?
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Hey man, thanks for the help..
I have new everything. New trans, new 3.5" one piece shaft(made by inland) new yoke & spicer joints. yoke is out 1.5 inches due to bowtie overdrive's warranty specs.
The entire drive-train under my truck had been replaced with all new items. In whole I maybe have 1000' total miles on some of the parts and even less on most of them.

Engine > 5000 miles
New Trans (BowtieOD 2004r) > 500 miles
New drive shaft,u-joints,yoke >500 miles
Rebuilt 12bolt (all new bearings, eaton posi, gears, axels, ) > 500 miles
New shocks > 200 miles
New springs >1000 miles

ever since I dropped the rear of the truck (5" drop springs) I have a bit of a vibration at higher speeds.
I have even blocked the rear end up and ran it up to 80 mph to see if the rear-end was the problem, and the gears don't howl...

I guess I just have to try the rear-end shim and see what happens.

Again, thanks for all the input... please keep the ideas coming, I have to be over looking something if these shims don't work....

Scott

[brad_man_72]

Inland does good work
Did you just buy a shaft (no joints or trans yoke) from them or did you buy the shaft assembled? If it wasn't ballanced all together its like ballancing a wheel before you mount a tire.
You said keep the ideas coming.... sounds like you're on the right track with the angle problem.
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[AustinScott]

Originally Posted by brad_man_72

Inland does good work
Did you just buy a shaft (no joints or trans yoke) from them or did you buy the shaft assembled? If it wasn't ballanced all together its like ballancing a wheel before you mount a tire.
You said keep the ideas coming.... sounds like you're on the right track with the angle problem.
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Shaft was built by inland from yoke to rear u- joint. I gave them the new yoke and told them the length and joint type I needed. They did the rest and supplied me with the complete ready to install unit.

Great company, great product. They only use top notch parts..
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[fleetsidelarry]

Scott, please let us know how the shims work out.

right now there's a difference between the front and rear u-joint angles, equalizing the tranny and pinion angles will equalize the u-joint angles and hopefully take care of the vibration.

the u-joint angles will be outside of "recommended" tolerances BUT whether that is a problem or not remains to be seen. another option is to raise the tranny CL the 1° you can get, and the pinion 2°. that would help reduce the u-joint angle, but not much.

finally, you could get rid of the 5" drop and go to a more moderate 3", that would help the joint angles also (but you'd need to do that before doing the shims)

[Super73]

Is your lift keeping the rear suspension compressed as if it was on the ground? Pinion and needs to be adjusted with the suspension loaded, like it would be on the road. Pinion angle will change loaded vs unloaded.
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[AustinScott]

Originally Posted by Super73

Is your lift keeping the rear suspension compressed as if it was on the ground? Pinion and needs to be adjusted with the suspension loaded, like it would be on the road. Pinion angle will change loaded vs unloaded.
Posted via Mobile Device

Hey man, thanks for info, I did take than in consideration when I did my measurements.
I measured the rear-end & shaft angles with the truck sitting on the suspension. The only thing I measured on the lift was the trans angle, & I had to measure the difference between the truck on the ground (frame reference pic above) & the truck on the lift (Frame reference pic above). I then had to subtract the difference between the two from the over all total of the trans angle. In my case this was only one degree.


Just to keep everyone updated:
I have been looking all over the place locally for these shims... no one has them, I guess my effort to keep my money in Texas is not looking so good. If I cant find them this week I will order them online.

Scott

[Super73]

When I had factory truck arms, I bought leaf style shim and drilled a section of the center out to accomodate the single u-bolt of the truck arm. It then locked in place between the rearend pad and LCA. You had to take the u-bolt out completely to get them in/out.

[AustinScott]

ok, well I couldn't wait any longer, I called carl's and ordered the two shims.

Should be here soon.

Sorry Texas, I tried !

Scott