Sweetstang84

So I am experiencing a problem: it seems I have found quite a few posts on it, in many different forums, but no real answers. I have a 2014 mustang v6 Automatic, with every power bolt on save for exhaust. I had a one piece DSS DS previous to the 3.73 install and everything was fine. My car had stock gears and I had a good ford dealership and mechanic I trust install the 3.73s. Now the car vibrates when you let go the gas at speeds over 60ish mph. The vibration increases if you go faster. It doesn't vibrate much when you accelerate or are holding the gas cruising at high speeds, it only does it primarily when letting off the gas. This only started after the gears were changed. This only happened 2x, but the vibration got so bad at one point, the car threw a check engine light. I and the dealership checked, but no code was stored in the ecu. Since then, riding with the mechanic, the car did not throw a check engine light up to 100mph, but the vibration is very noticeable in the same fashion described previously.

We (The ford shop, american muscle and I) have already done quite a bit of trouble shooting. They are Indexing the DS 180 degree to see if that helps or makes it worse, but I don't have the results back on that yet.

As I mentioned, this seems like it is a more common problem that no one is addressing and has more questions than answers on the cyclone V6 after a gear install. I am having AM and many other shop experts saying it could be everything from the Diff, the balancing of the driveshaft, to the imbalance of the engine/engine movement/motor mounts. It seems like a systemic elimination of each possible problem is needed, but someone must have had a solution/explanation for this. Seems simply like a combination of the higher speed of the one piece driveshaft related to the higher gear ratio leading to a vibration/harmonics issue. It also seems like a ton of people have done the 3.73 install on the v6 and have had no problem. But what is the solution/is there any, do all V6 owners who do this experience this? Will it cause damage or do we just live with it. Thank you for any help.

David Young

Well, if it never vibrated until the gears were changed, the gear change is causing it . Indexing the driveshaft can fix the vibration on some Mustangs .


I must add: My local Ford dealer changed my gears from the factory option 3.31's to the 3.73 gears that I bought from American Muscle. I do not have a 'vibration' I have an Axle Exchange aluminum driveshaft I have read about a few problems with the balancing of the DSS driveshaft

Bert

My SWAG is, you're probably right about this: The driveshaft is turning faster now with the 3.73 rear gears so that probably accentuated a vibration problem that was always there but was less noticeable at lower driveshaft speeds.

I believe the DSS shaft has a CV joint so pinion angle is supposed to be not critical. But it might be worth checking the pinion angle anyway. I have heard that the downside to the CV joints is that they do have some slop and they can induce vibration in some cases, maybe this is one of those.

Sweetstang84

Thank you both for the feedback, I tend to agree with both accounts. I really tend to believe though it may be something with the DS and not the gears. If something was really up with the gears, i think I'd be having a lot more problems at 100. I will mention the pinion angle, however my car is also not lowered, I'm at stock ride height. In addition I have also gotten the car up to 135-140 mph b4 the 3.73. and never had chirp. I will look into the CV.

David, so is the DSS DS crap you think? I've heard mostly good things and that they are a reliable shop. It was a **** expensive mistake then, 700$...

Glenn

I would try the easy thing first which is unbolting the ds from the rear end and turning it to the next set of mounting holes.

Sweetstang84

Ok so partly good and interesting updates. First kudos for all the advice! So, they indexed the DS 180.. and guess what? The vibration pretty much went away. Gotten the car up to 100ish, feels pretty good. The car especially at 60-70 when I heard a minor vib. before, I feel nothing but road now. I don't push it must past 100 now bc of temp and I'm running the all season stocks in winter. There might be a little vibration but that could be anything traveling at that speed, I would consider the issue resolved.... except... during one pull, I was at about 80-90 and let my foot off the gas. Car slows down and no vibration this time, however, the check engine light still went off! Flashed for a few seconds after I settled at 60 and went away. WTH is still going on?? Vibration is pretty much settled now and the car runs great, but check engine still happens... I'm at a loss. I'm going to try and work with BAMA and datalog the car to see if they can find something. The guy at bama said he thinks I have a ghost car... lol. BTW the car did not throw a code that was saved with the check engine light this time again. So still no engine code stored. PS here is a snippit.

Bert

great idea, and easy too . . . if it is a balance issue, this might cure it

David Young

I wouldn't say DSS driveshaft's are crap but, most of the people with vibrations from bad balancing seem to have a DSS driveshaft. Just from what I have read on Mustang Forums