tgui

I'm stuck. I have a vibration at 60mph. It starts at 50 and ends at 65.

Before my 80e swap I had no problems.

What I've done.

- fancy new custom driveshaft $$ that I installed tonight
- wheel balance and rotation
- alignment
- removed front driveshaft

Any ideas? Here are some thoughts

- can something inside the 80e trans I built be off balance?

- I didn't align my flexplate with the removal bolt hole

- Circe D torque converter off balance?

- truck sat for almost 4 months with front tires on ground. Rear were always on stands. Flat spots on tires that a Sears balance missed??!!

- I had to open the xfer case and install a new input. I replaced some bearings as well. I hear no bad noises but could something be wrong inside it?

Fuuuudge!! What's going on??!?!

Here are some pics of the new driveshaft compared to the rusted stock, and modded eBay stock I tried first. It's steel fwiw.

tgui

I feel it in my feet and steering wheel and a little in the butt.

I replaced front hubs 2 years ago.

Jetn3

I'm not sure how the 4wd are, but on the 2wd I noticed that on the 80e the output shaft sits lower on the crossmember compared to the 60e. I had to shim my 80e up a bit, about 3.5" to get correct u joint angles.

tgui

Did that help with vibrations?

So you had to lift the trans 3.5''?!! Wow

Jetn3

Yes, it did help but I have a crew cab and 2wd. I also did a 2 piece driveshaft swap, originally had long 86" aluminum shaft. I also have 2" drop shackles to level the truck and all my u joint angles were way off. I had to shim my trans, carrier bearing and rear end to get good angles.

Can you check the angle of the 80e output shaft vs pinion yoke angle?

Hope you get it sorted out

1bad2k

iTrader: (11)

You lifted the tail of the trans 3.5"? Man, that seems crazy but if it works. How did this affect the motor mounts? ..... I have the same issue as well with my 4x4 rcsb 4l80e swap. I was planning to shim my transcript up, but I was expecting to be in the .25-.5" range.

tgui

What MPH does yours vibrate?

tgui

GMCTrk must be banging his head on the desk seeing this thread. He's all over the place in multiple threads with "check ujoint operating angles". lol

I've attached a Dana PDF on DS angles that I found elsewhere on this forum.

Like Jet said, the 80e does sit lower on modded cross member. I'll crawl under the truck Friday and get rough measurements and then cut some shims out of some aluminum bar I have lying around.

I should have measured angles when stock. ****.

1bad2k

iTrader: (11)

My transfer case is -5° and my diff is +5°. Truck vibes at around 30-40 a little then comes back in at about 65 to 75. Sometimes at 80+ is goes mostly away. I need to lower the truck finally, shim trans up, set the rear pinion angle, and order a custom driveshaft. I've just been too lazy lol.

Wolftrk99

iTrader: (5)

After you check your u joint angles check the front end and tire balance, should not feel a driveshaft shimmy/vibration in the wheel.....