Drive line angle

[Bolted to Floor]

I need to check the drive line angle and don't want to spend the time to learn how to interpret the angles. Can someone tell me how good or bad am I looking??
The tail shaft is 5 degrees down
The pinion is 1 degree down.

Any help is greatly appreciated. This thing is going back together tonight.

[jayb]

Usually you'd like the pinion to be 2-3 degrees down from the transmission output shaft.  If I understand you correctly, a line coming directly out of the back of the transmission towards the rear of the car  is 5 degrees from level and would eventually hit the ground, and a line coming directly out of the pinion towards the front of the car is 1 degree from level and would also eventually hit the ground.  So, right now based on that you're angle between the two is six degrees.  So, if you were to rotate the pinion so that it was pointing up at 2-3 degrees, you would have the idea angle.  However, as it is you're not too bad, and what you could do at some point is buy some of those pie shaped wedges that go between the leaf springs and the axle housing, to raise that pinion angle so that it was pointing 2-3 degrees up.

In any case though, the way it is now won't cause any short term problems. 

[Bolted to Floor]

You accurately comprehended my jibberish!!

Thanks Jay

Edit for spelling

[Stangman]

Ya know on a stock vehicle meaning not a tube chassis car why would the angles be off. The tranny
sits on the tranny crossmember and mount of course and the rear gets lined up by the holes in the perches. How could it be off enough for there to be a problem. I’m curious

[cammerfe]

A problem with any of the mount points can cause difficulties. Did you ever see a leaf-spring car 'dog-track'?

KS

[Bolted to Floor]

Ya know on a stock vehicle meaning not a tube chassis car why would the angles be off. The tranny
sits on the tranny crossmember and mount of course and the rear gets lined up by the holes in the perches. How could it be off enough for there to be a problem. I’m curious

Hi Curious, I'm Exhausted... ...couldn't help it, just my poor since of humor. But I am really tired after today.

For my car, my TKO kit came either a cross member that lets the rear of the transmission point down more than it should. For the rear end, I added the extra leaf that was in the pack when I bought the car years ago to get a little more lift at the tires. I guess it could have caused a slight role of the pinion.

[Heo]

My opinion on this! in a perfeckt world, when the carb is horisontal
the trans is 4 deg down and the pinion....well on rigid chassie with
say a fourlink the pinion should be 4 deg up teoretical. But under
load the pinion tend to climb, more so on leafsprings or a coil suspesion
with soft rubber rubberbushings. What you get if the angles is to much
off is vibrations in the driveshaft. If you have vibrations do like Jay says
and try to wedge up the pinion.

[My427stang]

I like to see three numbers.

1 - Output shaft angle
2 - Driveshaft angle (installed, weight on wheels)
3 - Pinion angle

Under hard acceleration output and pinion angle should be within 1 degree, but it's often difficult to determine that, so some fudge is added based on what you think you have for pinion movement. The trade off for u-joint plane misalignment is vibration


Additionally, the driveshaft angle, when compared to the other angles, determines u-joint operating angle, and Spicer recommends max 3 degrees as a conservative number for any speed a car may likely go, there but never under .5 to ensure the u-joint rollers keep moving.  Sometimes that is not achievable, so you need to look at expected driveshaft speed.  The trade off for more operating angle is shorter u-joint life and vibration

With 5th gear and a decent gear ratio, your engine speed may be well under control, but the driveshaft speed will be higher, so the more care you put into this, the better.  An example of a 3.70 geared car with 26 inch tire, is a driveshaft speed of 4783 at 100 mph. (shorter tires and more rear gears will be worse)

Just because I have some Spicer tables that address this, I'll use Spicer again, they recommend a max u-joint operating angle of 3.7 degrees for a 4500 rpm driveshaft speed and 3.2 degrees for 5000 rpm..  So there is some fudge factor from the original 3 degree recommendation, but remember, that RPM ignores the 5 speed, and those of us with overdrive can easily hit that driveshaft speed. (4780 * .82) = 3919 engine RPM with a .82 OD, and 3059 engine RPM with a TKO-600 with a .64.  Even if you aren't driving around your local area at 100 mph, keep in mind, engine RPM in 4th as you enter the traps = driveshaft speed, so 4700 is realistic

So without knowing your driveshaft angle, we don't have all the pieces.  However, I can say, compared to the body, the stock output shaft angle on a Mustang is 3 degrees, and if you have a TKO crossmember that didn't require trimming of the floor, your numbers make sense.  I chose not to run it that way and added .750 (I think, it's been 12 years) under the transmission mount to get there.

What I have been doing since the Mustang install is start with a measurement from the center of the output shaft to the floor before I pull the old factory tranny.  Then I match it, and even with some slight differences in length depending on spacers, bellhousings etc, I am usually very close and usually exact where I want to be.

[wowens]

1 agree with Jay, you should be good to go. However, if you shim make sure you don't go up too far with pinion, it should not be angled above drive shaft. If you change, I would rather see trans go down a little.

[Phil Brown]

https://youtu.be/gmV4qwLfOMY
Interesting video about drive shafts and what happens with angles

[66FAIRLANE]

I did a lot of research on this when I fitted my GV unit. Heres what I determined, lifted from my old post.

"After much research on driveline angles (and there is plenty of misinformation and lack of understanding out there) these are the rules I am playing by, There are only 2:

1) The output shaft of trans and input shaft of diff (yoke) should be parallel to within 1 to 1/2 a degree with the diff pinion being down that 1/2 to 1. Diff pinion angle is all a compromise. With a leaf sprung car the more hp and the more strip time it sees the more angle down on the diff pinion. As this is a street car I will shoot for the 1/2 to 1 degree down. This keeps the operating angles of front and rear unis very close to equal.

2) These shafts should be brought to within that tolerance in such a way as to try and ensure that the operating angle of the unis does not exceed 3 degrees. This is for a hottie. Standard passanger cars & 4wd's etc can tolerate angles up to 7, but angles within 1/2 to 3 degress are more desirable. Operating angles of 0 degrees are a no no.

End of story and no debate will be entered into. There is enough debate out there on other forums and beleive me I think I have read it all!"

[My427stang]

I did a lot of research on this when I fitted my GV unit. Heres what I determined, lifted from my old post.

"After much research on driveline angles (and there is plenty of misinformation and lack of understanding out there) these are the rules I am playing by, There are only 2:

1) The output shaft of trans and input shaft of diff (yoke) should be parallel to within 1 to 1/2 a degree with the diff pinion being down that 1/2 to 1. Diff pinion angle is all a compromise. With a leaf sprung car the more hp and the more strip time it sees the more angle down on the diff pinion. As this is a street car I will shoot for the 1/2 to 1 degree down. This keeps the operating angles of front and rear unis very close to equal.

2) These shafts should be brought to within that tolerance in such a way as to try and ensure that the operating angle of the unis does not exceed 3 degrees. This is for a hottie. Standard passanger cars & 4wd's etc can tolerate angles up to 7, but angles within 1/2 to 3 degress are more desirable. Operating angles of 0 degrees are a no no.

End of story and no debate will be entered into. There is enough debate out there on other forums and beleive me I think I have read it all!"

No debate here, well said!

[Bolted to Floor]

Thanks for all the responses.

Too be fair to you guys, I had one of those moments where I can't comprehend the numbers I'm looking at on the protractor. I didn't realize it till I took the reading off the drive shaft and saw which side of the 0 the needle was on, then went back to the pinion out of curiosity. And it was on the same side as the driveshaft, so, I screwed that up!! 

The car is back down off of jack stands and I drove it to work this morning. I will be taking another look at the drive line angle this afternoon when I get home and report back with findings and pictures.

[BattlestarGalactic]

I know my wagon is all kinds of odd when it comes to angles.  The motor/trans points down in the back horrible.  I've never been able to raise it up to make the numbers more "correct".  In 23 yrs of racing, I can't even recall what the numbers are.   As long as it doesn't vibrate OR throw the driveshaft out of the car....it must be good enough.

When I put the third transmission in the Mack, I did work to make sure the angles cancelled themselves out.  Same kinda deal.  Motor/trans points down, so I had to tip the third transmission up in nose/down in back to even out the angles on the front u joints, then the rear was whatever it was.  I think it worked out okay.  Again, it doesn't vibrate and hasn't thrown the shaft out.

[Chrisss31]

"After much research on driveline angles (and there is plenty of misinformation and lack of understanding out there) these are the rules I am playing by, There are only 2:

I couldn't agree more, there is a lot of really bad info to sort through on this topic.  If you have a smart phone.....Tremec makes a pretty good app that takes the trans, driveshaft and pinio angles into account and gives a go/no go evaluation.

[Falcon67]

I make sure they are not parallel.  If they are each about 2 degrees out from each other, it's good.  I've done a lot of reading and run a lot of drivelines - drive line / pinion angle never did anything for traction or 60', unless your pinion angle approaches 90 degrees in either direction.  180 is worse, seen that also.

[The Real McCoy]

Tremec has a drive line angle finder for your smart phone.  It also has some calculators for MPH, RPM, and Tire Sizes.  They all seem to work pretty slick.

http://www.tremec.com/menu/tremec-toolbox-app/

[Bolted to Floor]

Tremec has a drive line angle finder for your smart phone.  It also has some calculators for MPH, RPM, and Tire Sizes.  They all seem to work pretty slick.

http://www.tremec.com/menu/tremec-toolbox-app/

I will take a look at that. Thanks

[My427stang]

You can also just use the compass on your IPhone, swipe left to the angle feature

[Pentroof]

And for easiest measurement of the tranny output, I put the edge of the phone across the tops of the oil pan bolts.
For the diff measurement, I put the phone vertically against the pinion yoke bolts and calculate a 90 degree offset.
This is just for simplicity and they are always spot on. Trying to measure from the face of the joint caps or something just gets squirrelly.
And make sure the weight is on the wheels when you measure! A 4 post lift is handy for this.

[Bolted to Floor]

Thanks for the tips guys. I didn't realize it was that easy to measure angles with an IPhone. I used the TREMEC app for the calculator and got a passing score 3 out of 4 tries. I will get the car up in the air again next week and take the readings were Pentroof suggested cause it did seem “iffy” at times if I was actually flat across the joint caps.

[My427stang]

What did you get for all three angles with weight on the wheels?

[Bolted to Floor]

Ross, the transmission was 6 degree down, driveshaft 5 degrees down and pinion is 7 degrees down.

[My427stang]

Ross, the transmission was 6 degree down, driveshaft 5 degrees down and pinion is 7 degrees down.

So given these numbers, I don't think you are bad at all with static numbers, but under any acceleration, as I said in the other post, without some sort of traction bar, you are likely over-centering a little as the pinion comes up.  My guess is with even the slightest acceleration you are likely tranny 6, driveshaft under 5, and 5 or even less on the pinion.  Numbers don't look bad but that pinion will always be trying to unload as load changes and on hard acceleration could be rising a lot more

This isn't the greatest video, but take a look at how much pinion angle can move, just on the street

https://www.youtube.com/watch?v=54_6GaYJvWI

If you are confident in your numbers, my choice would likely be to leave it as is and add an cheap under-rider bar.  However, if I was tweaking it, I'd likely add a little shim under the rear tranny mount, to the point where I didn't have to cut, just to correct back a little more.  Not sure if you could get to tranny 5, driveshaft 6, and leave the pinion alone but control it with the bars, that likely would work out pretty nice there without cutting the floor  (assuming you have good fan clearance).

[Bolted to Floor]

Thanks Ross. I will see what I can fit in for a shim at the transmission. I did measure from the fan to the radiator today, there was 1-1/2” at the top and about 1” at the bottom.

[My427stang]

That fan spacing makes perfect sense.  I used just under 3/4 of an inch of spacer in my own, but it really depends on cross member design.  Needless you say you can't tuck it all the way up without cutting the brace, also watch for the vent in the front of the tranny, right under the radio, but if you can get closer it'll only help.  Good setup work.

FYI - If you decide not to go with underrider bars, you'll likely have to drive the pinion a little lower.  I recommend against it though, it's a catch 22 if you don't stop wrap up.  No bars you need more angle, more angle means more vibration at cruise.  The ones below I have on mine are cheapies, I think I paid 69.99, but they sure do the trick, and have done so since 2005.  Same as the link below

https://www.summitracing.com/parts/sdk-tm-1069-p?seid=srese2&cm_mmc=pla-msn-_-shopping-_-srese2-_-scott-drake&utm_source=bing&utm_medium=cpc&utm_campaign=Bing+Shopping+Ads&utm_term=1100100889323&utm_content=All+Products

Of course there are fancier methods if you plan to race.  Caltrac springs have a strong front single "leaf" that doesn't bend much and the rear of the spring does the work, combined with Caltrac bars, it'll hook like nobody's business, but 100 bucks versus 800 or so, depends on your intended use.

[Bolted to Floor]

Well....I noticed after the trip the tire was rubbing more when the car was empty. When I got to looking, I found a new twist, I guess bend is a better word.





The new Grab a trak 4 1/2 leaf standard eye springs are on order along with 1/2" lowering blocks and a 2 degree shim. How the car sits, the pinion angle, and if I can get a shim under the transmission mount will dictate what I use. I will also try to use one or the other to center the rear end in the car.

Some sort of traction device is on hold till I can get the new stuff installed.