I'm at my wits end.

I've been attempting to fix this problem for months now.

I got a 4.10 gear change from a 3.55 from Steeda and have developed this very violent undercarriage vibration at speeds over 85 mph.

my truck has 5000 miles on it with an aluminum drive shaft. at 85 mph my rpm's are at 2800, which is not that high.

I took my shaft to have it balanced. this did nothing. at 2800 rpms, i shouldn't of needed it anyway. I paid 160.00 for nothing.

I took it back to Steeda and they took it apart and rechecked everything and said everything was installed correctly.

The ujoints are brand new and are ok. Nobody can figure out what this is. They are beginning to use the excuse that the aluminum drive shaft is not capable of handling a 4.10 gear, which is not really that much different from the 3.55. Only 10 mph difference. Not a huge change.

I've known so many people that have had this gear change done with no problems.

If you've had this done with no problems, please repond and tell me so. That I can print this page off and bring it to Steeda.

If you know what could be wrong, please also let me know, so I can print this page off and bring it to Steeda.

Thanks

Tom Longo

 

are you tires balanced? is tranny full? have you checked out your front end. bad shocks could do this as well.

 

Driveshaft wrap is a possibility - if this is being experienced during hard accelleration (?drag racing?).

Clearly if this is not the case, something is grossly out of balance. Were this the ring gear - or the pinion - a dial indicator would be your tool of choice for determining that (I am thinking that possibly the ring gear was misdrilled at the factory for the mounting bolts or the pinion was not chucked up correctly in the mill/lathe).

. . is there ~any chance~ that "someone" snuck a can of liquid "fix-a-flat" in one (or more) of your rear tires and let it harden in one spot?

. . just thinking outloud.

 

Well, the ring and pinion is Ford Racing, so I expect the best quality. I think if it's anyones fault, it would be the Steeda mechanic not taking his time to get the alignment perfect.

It's definetely the drivetrain, not the tires.

I had one performance shop tell me that the aluminum shaft wasn't meant to spin that fast! That's bull.

The gear change only dropped my speedo 10mph, that's nothing. So if I'm getting violent vibration at 85 now, than I should have been getting the same vibration at 95 before. And before the gear change I used to go 110 with the speed limiter raised by the Diablo chip. So that's not true. Plus, if Ford is that chincy to put that week of a drive shaft on, whereas it can only spin you to 95mph, than Ford bails and Chevy and Dodge rule. Because my buddies Dodge Crew Cab Long Bed has seen 135 on the highway, and his shaft is longer than mine. So I think that's just a sorry excuse for doing a bad job.

Steeda better fix it. I'm taking it in on Wednesday and have them pull the whole thing apart.

What I would like to do is print this page off and bring them a copy.

So....

Anyone who has done a 4.10 change, please reply with your results so I can show them that all these other people had the same change and none of them are getting this vibration.

Thanks,

Tom

 

Well I stick to my original suggestion I gave you the first time around. They screwed something up. Good luck let us know how it goes and weather or not they fix it, as I still would like to see what you run in the quarter with that six and nitros. You said you know for sure it isn't the tires have you checked. Just this week I noticed a vibration at 65 put new tires on (needed it anyway) and the vibration is gone, I don't think that is your problem but it is possible none the less, maybe the tire went flat and as previously mentioned someone at steeda fixed it for you with a can of fix a flat. Time to talk to steeda, should they offer to take the rear apart you might return the ring and pinion for a new one just to rule that out completely. Later, again hope you get this thing taken care of

 

Well,

I'm sure it's not the tires. I was running almost new stock tires on the truck and had the vibration at 85. Then last week I put Kumho Ecsta's on and had them high speed balanced. It's definetely not the tires. Besides, I can possitively tell the difference between a tire vibration and a drivetrain vibration. A tire vibration is not violent, only annoying, because your suspension soaks up alot of the vibes, whereas a drivetrain vibration is very metalic feeling and sounding that you can hear throughout your truck.

We'll get it right eventually. I'm sure Steeda didn't align the pinion angle correctly or something.

I'm dropping it off tonight and I'm not going to pick it up until they fix the problem. I don't care if it sits there for 2 months.

Tom

 

Sounds like a plan.

 

It takes me alot to get frustrated about mods, but i'm really ticked about this. Especially some of the lame excuses I've been getting about how the drive shaft wasn't designed for those kinds of speeds......speeds?? 95 miles per hour with the stock gears?? that's not speed. By buddies Dodge super crew long bed will do 140 with no vibration. Excuses are like butt holes, everyone has one and they all stink.

Tom

 

There's a rubber lump at the top front of the 8.8 diff. It's some sort of vibration damper and is supposedly ratio specific. Possibly this needs replaced with a different one?

 

I've done so much research on this that it's coming out of my ears.

The problem is that a driveshaft as long as mine would usually come in a 2 piece. Two shorter shafts connected in the middle by a bearing housing welded to a support beam under your vehicle. Ford chose the easy way out and simply installed on long shaft. Until just recently, you couldn't even get an aluminum shaft this long. This is only a problem in the super cab V6 models. The regular cabs shafts are 3 feet shorter and the V8's shafts are shorter as well. I guess that Ford didn't think you would be driving at high speeds in a V6 F150, or be changing the gears for racing. Our shafts are 4 1/2 inches in diameter measured at the center. The only bigger shaft available is a 5 inch.

Now, only in theory, would a larger diameter shaft give me more RPM's. The problem here is the word "Theory". I've spoken to at least 20 different high performance shaft manufacturers and have received 20 different theory's on how this critical mass vibration works, and how to fix it.

Installing the 5" shaft, in theory, would allow me to obtain higher rpms...in theory. Nobody I talked to knows anything for sure. It is not an exact science. It is simply trial and error.

I'll install the 5" on Monday. If it works, it works. If not, then I'm stuck driving around at 80 mph.

 

paint a 6" wide white stripe across your rear wheels and look in the mirror whilst the vibration is happening . You should be able to see if the vibes are happening in sync with the wheel ( and diff ) or much faster ( 4.10 times )

 

Ok, I'll have one of those window/mirror trucks drive along side of me on the highway at 85mph.

I picked up my truck from Steeda and talked with him a bit. He said that every 4.10 gear change and Auburn lsd he performed, there has always been a vibration afterward. He called it "harmonic vibration" that is caused by altering the mathematical equations with the 4.10 gears as well as the locking diff. He said that with the locking diff, there is nothing to soak up the vibration any more and that everyting is spinning so fast now that your going to get some vibration and some speed. How much vibration and at what speed depends on the vehicle. All you can do is lessen the vibration, but you can't fix it all together. Because what you gain on the bottome end, you lose on the top end...logical. He said the larger diameter shaft will smooth things out but will never get rid of the vibration all together.

so we'll just wait til' monday and see what happens.

Tom

 

BTW, I asked the Steeda mechanic why everyone has different theory's about this and he said that they DONT teach this stuff in school, that it's NOT an exact science, and that each mechanic learns different things based on their experiences.

Tom

 

Interesting problem.... have a few comments that may be relevant....
From what I have observed, harmonic vibrations occur only in A) unbalanced rotating assemblies and B) inherent in reciprocating assemblies. Our piston engines (and some A/C's) use harmonic dampners. My rotary engine (I just went to look) does not have one! Therefore, I conclude, if there is a harmonic vibration in your drive assembly, it is because it is out of balance, not due to some inherent physics. (Otherwise, we would all have little harmonic dampeners in all our differentials, right?)
Secondly, a drive shaft is a drive shaft.... be it steel or aluminum. The aluminum will be lighter for an equivilent strength of steel. IF it is properly engineered, and we see no reason for it not to be, it will perform identically to the original.
Third, I have helped assemble one diff in my life with a bona-fide road race mechanic. The margin for error is unbelievably small. It was about 4 to 6 hours as best I recall some 10+ years later.
OK, with all that said, there is, in my mind, no excuse for your truck to vibrate besides poor parts/workmanship. I would try this:
(And this is assuming we can trust the driveshaft people balancing job, which is an everyday thing and pretty damn fool-proof.) Get the rear up on jack-stands, slip the axles out where they are no longer engaging, and spin that diff up to 85 and prove it is in that part of the assembly. Good Luck.

 

I don't agree with any of that statement. Although you get an A for effort.

This is exactly why I've spent so much time researching this subject.

Let's just say I discussed this issue in detail with 65 different mechanics who specialize in this area.

Let's also say that aproximately 50 of them answered my questions with my above statement, and the other 15 agree'd with yours.

In this business, especially when all is theory and comes only from experience on the job, one has to go for the Majority Vote.

The Majority of mechanics disagree fully with what you were saying, while a small group of mechanices will say that you are completely correct and that the others are stupid.

So, who do you believe? The 15? or the 45?

You gotta go with the 45.

Why do you think you see tandems utilizing a double shaft system? If what you say were true, then they could put a 22 foot long steel shaft on their tandem and, as long as it were balanced, could drive vibration free.

picture, if you will, a 22 foo long 3" diameter piece of steel.

if you held one end and I held another, would it not sag in the middle?

Of course it would.

If I placed a balancing weight in the middle of the shaft, would that keep it from sagging? NO.

That is what is happening to my drive shaft, in essence.

In it's high rotation, it is whipping like a cake batter beater.

balancing will not prevent that.

You need to research more and stop theorizing. It's too simple minded to say that if it were balanced properly than it should spin smoothly. Unfortunately, there are alot more factors involved.

I'm going with the 45.

Thanks.

Tom