Custom Driveshafts - A fix to driveline vibrations or a cause for their increase?

[noGreta!]

I had the exact same problem with my 21 when it was brand new. I ended up replacing the driveshaft and that totally cured the problem. The dealer wanted to perform a series of trials with hose clamps on the driveshaft and multiple road tests. I just ordered a new driveshaft and replaced it myself. I have very little trust in dealerships as I have worked in one for 15 years. What I found was that the factory driveshaft was not indexed correctly and simply repositioning on the rear flange probably would have fixed it. I have 6,000 miles since replaced and all is well. If you lay underneath and look at the rear differential flange it will have a yellow mark, make sure the weights do not align with that mark, you want the closest weight on the driveshaft to the rear diff flange to be 180 degrees off. I would start by checking that first.

So far everything points to the DS. Did you replace with another stock one, aftermarket or custom-made?

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[91gt331sc]

I bought a stock one from the dealership and installed it myself so I could make sure everything was re-assembled correctly and torqued properly. I would honestly check the mark on the flange to the rear most weight on the driveshaft. Mine came from the factory with the weight aligned to the mark, which is the "high side" of the rear. Typically you would not want those two together. I would be willing to bet I could have rotated the flange, bolted back together and it would have been good to go.

 

[jmagnus87]

I bought a stock one from the dealership and installed it myself so I could make sure everything was re-assembled correctly and torqued properly. I would honestly check the mark on the flange to the rear most weight on the driveshaft. Mine came from the factory with the weight aligned to the mark, which is the "high side" of the rear. Typically you would not want those two together. I would be willing to bet I could have rotated the flange, bolted back together and it would have been good to go.

This guy seems to know what he is talking about and what he is saying makes perfect sense to me. Once i had it out i would triple check im following his directions as to which direction the flange needs to be mounted. Real easy to mess up at the factory of the tech doesn't know about it

 

[noGreta!]

Super solid replies guys, I will look into that and check for the mark.

Thanks for all the info! I don't want to give up on this one.

 

[91gt331sc]

Good luck! Hope it helps you out. If you get there and have any questions shoot a couple of pictures and I'll try to help you out.

 

[SHOdaddy68]

In both cars I had multiple attempts at balancing and also completely new and different wheels and tires fitted. There was no chage at all...

OK but a driveline issue will not manifest itself in the steering wheel. It has to have something to do with the front suspension, brakes, wheel bearing(s), steering rack/tie rods or wheel/tire.

I know you said the tires have been checked and balanced, but, a tire can be perfectly balanced and still create a vibration that will be felt in the steering if the tire is not perfectly round.

There are also multiple ways to balance a tire. The best method is a dynamic balance with weights on both inside and outside edges of the wheel. Many modern alloy wheels can't take a wheel weight on the outside edge or owners choose not to put weights on the outside for cosmetic reasons. The only alternative is a "static" balance with weights only on the inside or middle of the wheel. A wheel that balances at zero on a static measurement will many times not measure out at zero for a dynamic reading. Most good tire shops can explain this too you and do what's called a "road force balance" which takes it all into account and will get you the best possible outcome.

I really hope you can get this figured out. Good luck!

 

[noGreta!]

OK but a driveline issue will not manifest itself in the steering wheel. It has to have something to do with the front suspension, brakes, wheel bearing(s), steering rack/tie rods or wheel/tire.

I know you said the tires have been checked and balanced, but, a tire can be perfectly balanced and still create a vibration that will be felt in the steering if the tire is not perfectly round.

There are also multiple ways to balance a tire. The best method is a dynamic balance with weights on both inside and outside edges of the wheel. Many modern alloy wheels can't take a wheel weight on the outside edge or owners choose not to put weights on the outside for cosmetic reasons. The only alternative is a "static" balance with weights only on the inside or middle of the wheel. A wheel that balances at zero on a static measurement will many times not measure out at zero for a dynamic reading. Most good tire shops can explain this too you and do what's called a "road force balance" which takes it all into account and will get you the best possible outcome.

I really hope you can get this figured out. Good luck!

Thanks bud. I have ruled out the wheels/tires because I have played with three different sets of wheels and tires and there was no difference at all.

However, the suspension, brakes, wheel bearings and rack/tie rods are still in the suspect line-up so you might be on to something there.

I will be giving the car another close examination over the weekend with everybody's suggestions in mind and report back.

Thank you all.

 

[SHOdaddy68]

Thanks bud. I have ruled out the wheels/tires because I have played with three different sets of wheels and tires and there was no difference at all.

However, the suspension, brakes, wheel bearings and rack/tie rods are still in the suspect line-up so you might be on to something there.

I will be giving the car another close examination over the weekend with everybody's suggestions in mind and report back.

Thank you all.

Are all of the wheels you tried out OEM Ford? Factory wheels are "hub-centric" while most aftermarket wheels are "Stud-centric" even with a spacer ring. More chance of vibrations with an aftermarket wheel.

 

[91gt331sc]

So in my case I did feel it in the steering wheel, dash, center console. I did not have steering wheel osculation, just felt a kinda rumble. I also have 2 other gen 3 mustangs in the household that experienced no vibrations at all, so I was able to swap wheels with them. They are both automatic cars and one has a carbon fiber driveshaft installed. I wanted to try the removed factory driveshaft from that car but mine is a manual transmission so they are different. Like I said earlier, before I spent any money I would check the basics ( motor mount nuts/bolts, crossmember bolts, even rear axle nuts) and the driveshaft clocking. I have seen a lot of weird things over the years but have had 2 manual trans s550's now that had driveshaft vibration issues. Both of the 10r80 cars we have are fine with no vibrations.

 

[jmagnus87]

So in my case I did feel it in the steering wheel, dash, center console. I did not have steering wheel osculation, just felt a kinda rumble. I also have 2 other gen 3 mustangs in the household that experienced no vibrations at all, so I was able to swap wheels with them. They are both automatic cars and one has a carbon fiber driveshaft installed. I wanted to try the removed factory driveshaft from that car but mine is a manual transmission so they are different. Like I said earlier, before I spent any money I would check the basics ( motor mount nuts/bolts, crossmember bolts, even rear axle nuts) and the driveshaft clocking. I have seen a lot of weird things over the years but have had 2 manual trans s550's now that had driveshaft vibration issues. Both of the 10r80 cars we have are fine with no vibrations.

Fun question, did you try by any chance shifting into 5th from 6th and hit the same speed on the highway? Because that would either make it violently worse or smooth out like the OP said over certain mph as the driveshaft would be spinning at higher rates...

 

[91gt331sc]

On my car it didn't seem to matter what gear it was in it was always at same mph range. It would do it in 3rd through 6th if you brought the car to the right speed

 

[jmagnus87]

Good to know, thanks

 

[rojizostang]

Fun question, did you try by any chance shifting into 5th from 6th and hit the same speed on the highway? Because that would either make it violently worse or smooth out like the OP said over certain mph as the driveshaft would be spinning at higher rates...

actually, no, the driveshaft doesn't change speeds. The motor does because of the different gear ratios in the tranny. driveshaft speed is constant as it relates to wheels speed and mph. you would need the transmission between the rear of the driveshaft and the pumpkin to accomplish what you're saying, like a corvette.

I test drove a used 2020 mustang gt pp1 with the 10a. It had enough of a driveline vibe that i didn't buy it. i don't think the vibes are limited to only 6m cars.

i just bought a '23 gt 10a, and it has no driveline vibes at all, even with aftermarket wheels, fyi.

 

[noGreta!]

In my case no difference at all in regards to the gear it's in as long as it hits that speed it shimmies.

 

[noGreta!]

... here's the vid I tried to take of the shimmy. My camera work sucks but you can tell a little ... It's not an F350 death wobble but it's there...

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