Decel vibration, thoughts?

[lee4him]

I'm experiencing a real bad vibration throughout the steering wheel and even my seat as I decelerate at lower speeds like 25 mph. If I'm rolling up to a stop light and am allowing the drivetrain to slow me down (not going fast just normal driving) it vibrates badly but as soon as I accelerate or step on the clutch, it goes away. I have Bruce's bushing kit installed with his recommended pinion angle set (I have tried changing the angle and that didn't help, so I don't believe it's the pinion). Any ideas?

 

[mu22stang]

Has the car been properly aligned post IRS installation?

Are you saying that this ONLY happens with engine braking, or it's worse with engine braking?

What gear(s) does this occur?

Have you recently done any brake work?

 

[lee4him]

Yes I've had a 4 wheel alignment done (2 weeks ago).
Yes, it only occurs when decelerating from say 3rd gear around 2k rpm and again in 2nd around 2k rpm (will do it in 1st gear too). There is absolutely no vibration on acceleration or at cruising speed. As for brake work, I have not touched the brakes. Even if I'm applying brake when The engine gets around the 2k rpm decel it will vibrate. Like I said though if I feather the throttle even slightly or engage the clutch, the vibration goes away.

 

[brian97cobra]

mine does it from about 100 down to 85 mph on deceleration. but i do not notice any vibrations upon accelerations up to 130 mph


try putting it into neutral and see if anything changes. mine didnt but perhaps yours will

 

[lee4him]

No I haven't noticed anything at higher speeds. I'm sure it's something simple...just want to figure it out sooner than later

 

[mu22stang]

Torque the lugs (95 ft lbs), the hub nuts (258 ft lb/240 ft lbs; F/R), and get under the car to recheck your work. Sometimes a clear head and 20-30 mins under the car can reveal something that was overlooked on a big suspension install.

Also, check in with Bruce. You really won't find more personal customer service in the market today.

 

[wilderyzed]

I hate to say it but it sounds clutch related like you may have broke a clutch finger or somethin may even be tranny wouldnt make logical sense for it to be suspension or pinion related to me, any clutch work been done? What clutch do u have how many miles?

 

[lee4him]

Thanks for all the great inputs! Last night I noticed my motor only sitting about a 1/16" from the steering rack and the oil filter had been making contact with the power steering lines. I raised the motor a 1/4" and I believe the vibration will now be fixed. I'll take it out for a test drive here in a few and let you all know the results. BTW, I bought the car as a project and it didn't have a motor only the AJE k-member. So when I installed the motor I never thought to check the clearance between the oil pan and the rack. If this doesn't solve the problem then the clutch is my next look.

 

[lee4him]

Well, it was a good thing to raise the motor but that wasnt the problem. So, I dropped the tranny and discovered a twisted input shaft! This answers another issue I had on the dyno the other day. We started to smell a burning clutch at about 5k rpm. Well it's a 26 spline so now I've got to source one, anyone know where to get the best deal on one?

 

[lee4him]

Just in case anyone else runs into a similar issue as me...the problem was a bent input shaft. Replaced it and all is good! My T. Is fun to drive again! (BTW, bought my replacement kit from AMP Performance. Highly recommend them. I dealt with Tom and other than him being a Michigan fan, he was a stand up guy).

 

[UFGatorGuy20]

Just in case anyone else runs into a similar issue as me...the problem was a bent input shaft. Replaced it and all is good! My T. Is fun to drive again! (BTW, bought my replacement kit from AMP Performance. Highly recommend them. I dealt with Tom and other than him being a Michigan fan, he was a stand up guy).

Yikes. Glad you found the problem!

 

[bigdog93lx]

I was going to say pilot bearing but it seems you found the problem. I was getting pretty harsh vibration when decelerating last summer, found out my pilot bearing spilled its guts and was causing my input shaft to vibrate like hell and pop-out of 4th gear.

 

[lee4him]

Only reason I found it was the grace of God! I had a noisy throwout bearing and dropped the tranny to replace it and the pilot bearing. Just so happened I spun the input shaft as it was siting there on the floor and i noticed it didn't spin true. So I removed it and sure enough it was bent. $475 later, no more vibrations!

Keep in mind I only felt the vibration at 1500 Rpm till about 1250 Rpm (off throttle, decelerating). I believe this is not a common problem but in the event you've checked everything else, this might help.