Driveline angle

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mjtjnj

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Hi all,
I bought a 2000 Sport 2
years ago, had a lot of work done badly to it, but the price was right, and the frame is clean. Very slowly (3 small kids) and with the help of a very kind local forum member, I took off the 4” coils, the MM lift and transfer case drop, the snorkel and the 33s, replacing all with stock and 31s, along with new control arms, ball joints, shocks, and complete steering replacement, from the box out. The only thing I left on was a 3” body lift. I didn’t want to do the work, and it doesn’t look bad, to me. I also found a disc brake Dana 44 and driveshaft and installed them.
Once it was finally road ready, I did a lot of around town driving and it did well. Once I hit the highway , there were vibes at 55ish. With all the time I’d spent under this Jeep, I missed the rear driveshaft angle (see pics), and always had been told that a body lift would not affect drivetrain angles, only a suspension lift would. Of course, I never heard it from anyone credible!
I really don’t want to do a SYE. Can anyone explain this phenomenon? Could it be fixed with a tummy tuck skid plate?
any ideas would be welcome!

thanks
Tom

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Has the motor mounts been lifted 3 inches also? How does the fan and fan shroud look?

The drive shaft angle, or lack of angle is certainly an issue.

Could be fixed by lowering or removing the body lift IF the motor mounts are also lifted 3 inches, which would appear to lower the transfer case output shaft angle downward towards the rear axle, like in your photo.

You could also get a belly-up skid, which would raise the transfer case and give better angles, or SYE, or both.
 
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Would be my guess also, there is a motor mount lift in place. The angle of the tail shaft on the transfer case should not be angled down.
 
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xXDavidCXx said:
Has the motor mounts been lifted 3 inches also? How does the fan and fan shroud look?

The drive shaft angle, or lack of angle is certainly an issue.

Could be fixed by lowering or removing the body lift IF the motor mounts are also lifted 3 inches, which would appear to lower the transfer case output shaft angle downward towards the rear axle, like in your photo.

You could also get a belly-up skid, which would raise the transfer case and give better angles, or SYE, or both.
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Superjay5 said:
Would be my guess also, there is a motor mount lift in place. The angle of the tail shaft on the transfer case should not be angled down.
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Thanks guys for the replies. That’s what I thought, too, so i removed the raised motor mounts and put on stock ones. Hasn’t changed things much.
 
mjtjnj said:
Thanks guys for the replies. That’s what I thought, too, so i removed the raised motor mounts and put on stock ones. Hasn’t changed things much.
Click to expand...

I would take a hard look at your transmission mount then….
 
It’s like you have lowered the Jeep below stock. What do your spring lengths measure? Front should be 12” stock. Rear should be 8” stock.
 
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JMT said:
It’s like you have lowered the Jeep below stock. What do your spring lengths measure? Front should be 12” stock. Rear should be 8” stock.
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I haven't measured them, but I bought them from someone I knew who had bought a new Rubicon in 04 and immediately lifted it, and had a stockpile of all his original parts, so I don't think they are an issue there. Chrysler parts.
 
The phenomenon is the angles have to oppose each other to cancel out or you get vibes.
 
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