HELP!! Driveshaft Angle Problems

[RONAELEGT550R]

OK guys, I need your help on this one. Experience might be needed on this. I have built my 05 to run so I had to beef up the drivetrain so I changed out the driveshaft to a one piece. I changed out the 3650 cause they suck on durability and replaced it with a TKO 500 built to handle 9.50's in the 1/4. I had to change the shifter to that funky extention type TRI-AX shifter to get it to hit the factory shifter location in the 05'. I have dropped the engine as low as I can go on my BMR "K" member so I could get the tailshaft of the trans up high enough to get my angles I needed. The engine is sitting at about 3 deg down. I have lowered the suspension about an 1" all the way around. Here's my problem. With the car sitting on all 4 on a level surface the rear pinion angle is set at -3.5 deg. The trans angle is 0 deg and the drive shaft is -0.5 deg. This nets me a 3.0 deg angle which sucks. They dont cancel out each other. I cannot get anymore angle at the transmission. I have moved the rear pionion angle all over the place and it doesn't get any better than 3.0. The drivetrain geometry of these car is screwed up. I know now why ford put a 2 piece shaft in these cars. Anybody got a answer or fix for this problem besides going back to a 2 piece shaft or change out to another $3000 transmission? Need help on this one guys. I am at my wits end!

 

[Natural1]

The more you lower the front of your driveline, the more out of wack, it is going to get. Your pinion centerline and the transmission centerline need to be parallel and should be within 1/2 degree. If the centerlines are off too far, the u-joints travel at different speeds causing vibration, which is obviously bad. I also don't see how the engine can be nosed down 3 deg and the tailshaft be at 0 deg. The tailshaft is either at 0 or it isn't. Is your transmount height an issue? With an adjustable UCA, there should be no issues correcting this. I would measure, rinse and repeat... Are your measurements correct? It seems like you need to raise the engine back up and point that pinion at the tailshaft. I'm sure you know all of this, but there has to be a mistake somewhere.

 

[jroc07gt]

dont they have motormounts that let you lower the engine down?

 

[Natural1]

That's what he did with the k-member, but with the trans swap, I would assume, a transmount has possibly fubar-ed his driveline angles, something else is just not right or the measurements are incorrect.

(Hotrodders.com had some neat reference drawings)

 

[RONAELEGT550R]

The more you lower the front of your driveline, the more out of wack, it is going to get. Your pinion centerline and the transmission centerline need to be parallel and should be within 1/2 degree. If the centerlines are off too far, the u-joints travel at different speeds causing vibration, which is obviously bad. I also don't see how the engine can be nosed down 3 deg and the tailshaft be at 0 deg. The tailshaft is either at 0 or it isn't. Is your transmount too tall? With an adjustable UCA, there should be no issues correcting this. I would measure, rinse and repeat... Are your measurements correct? It seems like you need to raise the engine back up and point that pinion at the tailshaft.

I'm sure you know all of this, but there has to be a mistake somewhere.

I think the reason its 0 is because of the 315's I have on the back. With the frame level the trans angle is -3.0 and the driveshaft is -3.5. With the car sitting on its tires it's 0 and the driveshaft is -.5 and the pinion is -3.5.I cannot get the front angle any better than -.5. Physically it cannot be moved anymore. If I go up anymore with the tailshaft the shifter linkage hits the transmission tunnel of the car. Its like the centerline of the rear end is too high in the car. maybe from lowering it caused this, I don't know but I cannot get good angles. I would love to have a -3.0 angle at the trans but I can't get it. Where do I need to start to try and fix this. Right now I have a pretty good vibration at about 60 mph and up. If I set the pinion at 0, the same as the trans the driveshaft is running up at the pinion and that is telling me the centerline of the rear end is too high in the car. if I try and raise the engine then the trans hits and it tilts it down even more so I am stuck between a rock and a hard spot right now. Got any answers?

 

[RONAELEGT550R]

dont they have motormounts that let you lower the engine down?

Yeah, that's what I did. I actually have it lowered as far as I can go without the rack hitting the oil pan and I even have a 7qt street/strip pan on it as well. I think with the TKO being shorter and the shifter on it lacking 9" from hitting the stock opening and me having to use that extended shifter that moves it back 9" to hit the opening, is causing some problems as well. I can't raise it anymore cause it hits the tunnel. If i could use the standard shifter like what was on my 3650 I could raise it about another 1" to 1-1/2". That would probably get me enough to correct the angles. But that would mean having to change trany's and I ain't got another 3 grand to change it out. I thought I was doing the right thing putting this one in bu looks like I didn't.

 

[RONAELEGT550R]

That's what he did with the k-member, but with the trans swap, I would assume, a transmount has possibly fubar-ed his driveline angles, something else is just not right or the measurements are incorrect.

(Hotrodders.com had some neat reference drawings)

I got a custom crossmember from ProMotion Powertrain and it fit great. I even had to shim it up to get it as high as I did. I just can't go anymore cause it's hitting the tunnel. I've spent hours under that car just scratching my head trying to figure this shit out. Now I'm just stuck.

 

[Natural1]

I don't know what the section width of the tires have to do with the pinion angle. Is the car level on jackstands or on a 4 post, when you are checking all of this?

 

[jroc07gt]

I don't know what the section width of the tires have to do with the pinion angle. Is the car level on jackstands or on a 4 post, when you are checking all of this?

he means the height of the tires

 

[jroc07gt]

Yeah, that's what I did. I actually have it lowered as far as I can go without the rack hitting the oil pan and I even have a 7qt street/strip pan on it as well. I think with the TKO being shorter and the shifter on it lacking 9" from hitting the stock opening and me having to use that extended shifter that moves it back 9" to hit the opening, is causing some problems as well. I can't raise it anymore cause it hits the tunnel. If i could use the standard shifter like what was on my 3650 I could raise it about another 1" to 1-1/2". That would probably get me enough to correct the angles. But that would mean having to change trany's and I ain't got another 3 grand to change it out. I thought I was doing the right thing putting this one in bu looks like I didn't.

you could try cobra jet springs in the rear since they dont lower very much.

 

[RONAELEGT550R]

I don't know what the section width of the tires have to do with the pinion angle. Is the car level on jackstands or on a 4 post, when you are checking all of this?

I have it sitting on ramps while I am checking it. jroc07gt was right. the height of the rear tires is quite a bit more than the front and that is where I am getting the rake in the car from rear to front. You have to check your drivshaft angles with the car loading all for corners to get it right. If I put it up on jack stands and level the frame then the trany angle is -3.0 where alot of people recommend it be set. My problem is that the driveshaft doesn't run down from front to back it runs upward. I'm thinking it's the Roush springs and struts that have created this problem. They lowered the car but raised the rearend too much. I'm just wondering if I change them if it's going to have a funky look with the rear end being even higher. Right now the center line of the rearend is higher than the centerline of the trany. That's the problem I don't know how to fix? How do all these guys that lower or slam their street cars not have drivetrain problems? They should be tearing crap up with them siting as low as some I have seen? Blows my mind!

 

[Natural1]

You have to check your drivshaft angles with the car loading all for corners to get it right. If I put it up on jack stands and level the frame then the trany angle is -3.0 where alot of people recommend it be set. My problem is that the driveshaft doesn't run down from front to back it runs upward.

I don't see that being a problem, with any forward driveline angle (engine/trans) you experience, the angle of the pinion needs to be parallel (or somewhat) to the trans output. This may change based on your type of driving (racing), as you may run a degree or so negative to compensate for driveline slack or axle movement on launch or run it straight up (@0) on a road course. As long as the angles are parallel, the driveshaft won't care what it's relative location to the ground is. I would try to get the trans angle back as close to 0 as you can and then change the pinion angle to line up parallel. With your driveshaft running backwards (uphill the wrong direction) you can't have a positive pinion angle. [scratches head] If it is above the transmission centerline, you need to point the pinion at the talishaft. The attachment will be invalid based on your current situation.

 

[RONAELEGT550R]

I don't see that being a problem, with any forward driveline angle (engine/trans) you experience, the angle of the pinion needs to be parallel (or somewhat) to the trans output. This may change based on your type of driving (racing), as you may run a degree or so negative to compensate for driveline slack or axle movement on launch or run it straight up (@0) on a road course. As long as the angles are parallel, the driveshaft won't care what it's relative location to the ground is. I would try to get the trans angle back as close to 0 as you can and then change the pinion angle to line up parallel. With your driveshaft running backwards (uphill the wrong direction) you can't have a positive pinion angle. [scratches head] If it is above the transmission centerline, you need to point the pinion at the talishaft. The attachment will be invalid based on your current situation.

Got any suggestions on how I can get the tailshaft to 0? It physically cant be raised any higher because of the shifter linkage hitting the tunnel. I can't be the only one that has had this problem. Thanks for all the info on the angles!

 

[jroc07gt]

the only thing that can raise or lower the rearend is tires

 

[rojizostang]

Got any suggestions on how I can get the tailshaft to 0? It physically cant be raised any higher because of the shifter linkage hitting the tunnel. I can't be the only one that has had this problem. Thanks for all the info on the angles!

i haven't read this whole thread...but have you tried driving the car, or are you just assuming you're going to have a vibration?

 

[RONAELEGT550R]

the only thing that can raise or lower the rearend is tires

tires actually raise the whole car. Changing springs lowers or raises the rear end in the car. That's why when you buy a lowering kit you get shorter springs. you install them and the car sits an 1" lower or more depending on the kit you buy, but you didn't change the size of your tires. You are actually raising or lowering the complete rear end assymbly relative to the horizontal center line of the car. That is what throws your driveline out of whack.

i haven't read this whole thread...but have you tried driving the car, or are you just assuming you're going to have a vibration?

Yes, I have driven it. It vibrates pretty badly. I am adjusting it everyday trying to find that happy medium. I just afraid that when its ready for the strip I may tear something up with it being out.

 

[rojizostang]

i bet it's the drive shaft.