Neal,

I recently changed from 3:55 to 4:10 gears. Now, I am experiencing a strong vibration and rumble sound from the driveshaft at speeds above 80 MPH. I am running a 31.6" tires on an extended F150 2WD. I have an aluminum drive shaft if that matters. Did you experience this problem with your gear change and if so, how did you eliminate it? I read an old post on this issue which suggest changing out the drive shaft with one that came stock with lower gears, such as a Lighting.

Any advise is would be appreciated. With a 4.6, I don't regret changing out the gears, but would like the option to go faster than 80 MPH if needed.

Thanks.

 

Crain do you have an aluminum driveshaft?

Check this search out. A lot of us got this when we got gears done.

Good luck.

 

If you want, Neal to specifically address a question, I'm not going to answer. I will point out however, that this is what will happen to your transmission tailshaft housing if you go too fast

 

That's one hell of a paper weight you have on your desk!

 

Guys...thanks for the replies. AjRagno...Neal is not the only one that can answer my question. I appreciate your reply under the suspension forum and sent a note to the guys at the shop where I had the gears changed regarding your note. Unfortunately, I have not been able to talk to them this weekend. I turn my truck into them in two days and wanted to have a proven solution for our trucks that I could share with the shop manger. I have read the old posts that offer some suggestions to fix the problem. The only one that sounds as if it would correct the problem was to change out the drive shaft but unless I missed it, no one has actually corrected the problem in this manner either. There are several suggestions but no reply by anyone that had the problem and fixed the problem. Since Neal races his truck, I assumed he had found a way to fix the problem.

 

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crain,

Is the vibration when acclerating, ocasting or when driving steady? Did your shop index the drive shaft to the output shaft in the tranny? Check the bushing too. Check the U joints and the driveline angles.

Regards

Jean Marc Chartier

 

The vibration is in direct response to accelerating over 80MPH. If you back off the gas, the vibration and rumbling from the drive shaft decreases and stops below 80MPH. As you accelerate faster and faster, the vibration and rumbling gets worst. I got up to 87MPH and decided not to go any faster because the vibration and noise was so bad.

The shop I went to rotated the drive shaft 180 degrees and checked the other components of the tranny. They were going to check the angle tomorrow, but from the other post, I don't think it's the angle as much as it is the type of drive shaft that comes with the truck. If I never hit 80 MPH, you would never know I have a problem. Acceleration off the blocks is steady and strong with the 4:10s and responsive with my 4.6L at speeds below 72 MPH.

 

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I have a vibration in my truck too after I got gears changed.

I can start to feel it a little at 80mph but it's extremely strong at above 90mph.

I'm thinking it's a bad install on the gears though as the gears whine badly. They're really loud! And I had someone next to me and I got it up fast and he said he could hear what sounded like metal hitting stuff... And that's not a good sound...

I'm gonna take it back to the guy that installed my gears to see what he has to say.

He thinks it's the driveshaft but the truck didn't do this with my old gears, why would it do it now?

 

Because your driveshaft has a higher rotational speed with your new gears, resulting in the virbation showing up at a lower vehicle speed than it did before.

 

Neal...are you out there?