I'm guessing I toasted something.

codemonkey · Apr 21, 2005

So last night I was on I-5 driving along and another mustang came up and wanted to play. I took the bait. I don't know how fast we were going (My speedo tops out at 85), about 4500-5k rpm in 5th. I'm guessing around 120-130. Way above topped out on the speedo.

Anyway, there were no cars out there, and we just kept going for a couple miles. I started to pull away from him, and slowed down, as I saw a pack of cars about a mile ahead, and decided not to screw around.

Sure it was good natured fun, but I think I screwed myself. Now I have a shimmy in the car that I can feel, especially at high RPM. Its in every gear, and its not really anything large, its barely noticable. Me thinks it may be my rear differential. I'm dont claim to be a master mechanic, but thats my best guess.

Kind of sucks, I think I'm going to the open house at BO on saturday, but I dont think I'll be racing that night. I dont feel like calling a tow truck when I grenade the rear diff on the topend. Kinda sucks.

What do you guys think? My imagination, or does this sound familiar to any of you? Might see a WTB post from me soon

stangman393 · Apr 21, 2005

Bring it over tomorrow and we can check it out. Good time to switch to 3.73's. Dont wiat til it blows up. You will end up needing more parts.

Jeff

gospeedgo · Apr 21, 2005

heres a way to narrow down the possibilities....I assume it isnt vibrating at idle when the car is still. Go fast enough to make the car shimmy, take it out of gear so the engine is just idling. Is the vibration still there?

89MustangGX · Apr 22, 2005

It's probably your imagination.

As for the speed -- your RPM/Gear calculations will tell you how fast you were going depending on the rear gears you have. Stock would be about 200MPH at that speed, so hopefully you have lower than stock gearing.

codemonkey · Apr 22, 2005

It does have lower than stock gearing. I was told 3.73 was what was put in it by the previous owner, but I can't say that for sure. I will have it checked out, before it breaks.

Let's hope its my imagination, but somehow I doubt it. Kind of on the same subject, how difficult is it to replace that 85mph speedo anyway? I dont really need it, only exceeded it 3 or 4 times since I've owned it, but it would be nice to know.

heres a way to narrow down the possibilities....I assume it isnt vibrating at idle when the car is still. Go fast enough to make the car shimmy, take it out of gear so the engine is just idling. Is the vibration still there?

Good idea, I'll try that tonight or tommorow.

ddonaca351 · Apr 22, 2005

Also try to pay attention to if the vibration goes away when you apply very, VERY light throtle.... but then returns when you let off at all (possible u-joint)

Or if you maintain speed, and push in the clutch does it go away? Then its could be on the motor (like a slipped dampner) because the rear end and driveshaft etc... will still be turning.

Or if the vibration seems to be the same at a given speed, no matter what the motor rpm is, then maybe you just lost a wheel weight, and you have a balance problem...

Dont panic, it could be very minor. But you do need to find out.

Oh, and on the gears...
-jack the rear up (chalk the front wheels, and use stands!) then mark one tire with a piece of tape or something, and mark a spot on the driveshaft, and turn the driveshaft while you count the number of times it goes around to one turn of the rear tire. If you get 3.7 turns, then wal-la you have 3.73s.

Dave-

f4fntm · Apr 22, 2005

Hmmm... could it be a driveshaft weight come off?

codemonkey · Apr 23, 2005

Yeah, its back to the drawing board. At least its not drivetrain, when I push in the clutch and coast, its gone.

Or if you maintain speed, and push in the clutch does it go away? Then its could be on the motor (like a slipped dampner) because the rear end and driveshaft etc... will still be turning.

This one is starting to make more sense actually.

redrumracing01 · Apr 26, 2005

check your driveline bolts every onec in a while mine come loose and the same thing happines and the i know its time to tighten them again

codemonkey · Apr 29, 2005

Well, I had AFP replace the harmonic dampener today, that wasn't the problem. It wasn't a total waste, Its better than stock, and I had them throw on some underdrives while it was apart.

It may need a full dianostic from AFP. I'm going to pull the motor and tranny mou nts out of it and try that, and kind of go from there

codemonkey · May 9, 2005

Well, I pulled out the drivers side motor mount and it was split in half. I replaced that one, and I have to pick up the passenger side tommorow. It is split as well, not sure if its all the way broke, but probably.

The shake is still there, exactly the same, with the new one on the drivers side, lets see if it does it with the passenger side. If so, I'm going to have someone smarter than me look at it.

I'm thinking maybe I busted a valve spring or have a clutch prob at this point. But, I do have broken mounts so at least I got them replaced.

gospeedgo · May 9, 2005

You did get the better convertible mounts right? Pretty close to the same pricing but much stronger.

I didnt even realize that was you that had the balancer and pulleys done...should have asked, we could have looked it over for you when you were in.

TheRedBlur · May 9, 2005

that sucks man, have you checked your U-joints yet? or does it stop vibrating when you hit the clutch?

codemonkey · May 10, 2005

You did get the better convertible mounts right? Pretty close to the same pricing but much stronger.

Nope, but the next time I'm at your shop, I'll pick up a pair.

I didnt even realize that was you that had the balancer and pulleys done...should have asked, we could have looked it over for you when you were in.

Well, I had Chung drive it while I was there, and he suggested looking at the motor mounts (he was right!), but he recommended having a full diagnostic done. I didnt want to be rude, since I was only scheduled for the balancer and pulleys, and you guys had others in the shop. If the new mounts don't solve the problem, I'll give you calls a call and setup an appt.

codemonkey · May 10, 2005

that sucks man, have you checked your U-joints yet? or does it stop vibrating when you hit the clutch?

It stops when I hit the clutch. It gets worse with increased load on the motor.

TheRedBlur · May 11, 2005

oh that sucks man

codemonkey · May 16, 2005

Well I replaced the other (broken) motor mount. I cant reach enough RPM to tell if it still has the shimmy.

Why? because I put a new intake and throttle body on it at the same time, and forgot to put the adjustable fuel pressure regulator in it (that I did buy, that both mischa and chung told me to put in.. DOH). Literally at the last point when I was filling my radiator back up, I realized this.

Anyways, now it really runs like *****, and I wont have the opportunity for 3-4 weeks to put that regulator in, so it looks like its a trip up to AFP again!

Getting really close to getting back up to speed tho. I can feel it!

stangman393 · May 17, 2005

Might have been cheaper for you to pay someone to diagnose it.

1993c0bra · May 17, 2005

I would Buy an aluminum driveshaft

codemonkey · May 17, 2005

Might have been cheaper for you to pay someone to diagnose it.

Well, I didnt get the intake and tb to solve this particular problem, I got those for the power . And with my current schedule, its really, really hard to get any kind of time to do this stuff. Usually, every 3rd or 4th weekend I get time off.

So far, if the motor mounts weren't the problem, I'm only out 36 bucks. They are both busted anyway, so it wasnt a waste. I am dropping it off at AFP today to have them put in the regulator and dyno tune it, so it should be back in action soon.

I'm guessing I toasted something.

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