Odd Shudder

The Goat · #1 08-07-2006, 02:57 PM

See, I *never* should have discussed selling the SVX. It's all-out mutiny now.

About a month ago, I started noticing a "shudder" when I pulled away from a stop. It happens at about the 10-15 mph mark. It doesn't happen at any other point, it's not a grinding of any sort, and if I accelerate *very* slowly, it's almost nonexistent. If I accelerate at a moderate or hard clip, it's very noticable. It's more than a vibration - "shudder" is the only way I can describe it.

Now - the tranny shifts *fine,* as it's done since I got the car a year ago. I've had the fuids checked, they're all clean. However...today the shudder coincided with a double "thunking" noise which, while it didn't sound remarkably alarming or ready to break apart, has me seriously worried. The seast of my pants tells me it's coming from the rear, and my brain says "differential"...what say the rest of you

(97 LSI AWD, btw.)

Earthworm · #2 08-07-2006, 03:49 PM

transmission mount?

The Goat · #3 08-07-2006, 06:21 PM

Interesting and cheerfully inexpensive theory - wouldn't it make that same shudder in every gear, though? (It doesn't...only in 1st)

Earthworm · #4 08-07-2006, 06:26 PM

Most people only notice the mount noise either during the 1-2 shift or when going into gear (D or R).

This would be my first suggestion in diagnosing the issue. Hopefully more people can chime in here with their experiences.

$ gest24 $ · #5 08-07-2006, 06:32 PM

I had a vibration under cornering and acceleration at 55mph and it turned out to be a split motor mount we found when pulling the engine this weekend.

nysvx10 · #6 08-07-2006, 07:44 PM

I have exactly the same problem. It is a tricky problem because there are so many possible causes. What would you look for when trying to decide if the tranny mount it bad? Will it be pretty obvious? I think that is probably a good place to start looking. I'm going to take my car into the shop that did my rebuild and have tranny/diff fluid changed, and see what he thinks might be causing the shudder.

The Goat · #7 08-11-2006, 05:22 PM

Not the tranny mounts; had them checked out.

It's Just Eric · #8 08-11-2006, 11:18 PM

Mabey have a look see at the rear diff. Also check up on play between the driveshaft and rear diff when you rotate the driveshaft by hand. It should engage almost immidiatly.
Could also be a neandertol in your trunk shaking the car whenever you accelerate. My money is on the later theroy

ShowNoMercy · #9 08-12-2006, 07:27 AM

My old 93 impreza ls used to do exactly what you said. I work as a mechanic and i drove my boss to pick up a car once and he told me it was the driveshaft bearing on the back of the tranny. My car shuttered real bad. My passenger seatbelt would rattle against the car.

The Goat · #10 08-14-2006, 09:11 PM

Quote:

Originally Posted by ShowNoMercy

My old 93 impreza ls used to do exactly what you said. I work as a mechanic and i drove my boss to pick up a car once and he told me it was the driveshaft bearing on the back of the tranny. My car shuttered real bad. My passenger seatbelt would rattle against the car.

Interestingly enough, I've kinda started thinking driveshaft as the source of the problem as well - it's started "humming" under deceleration at around 50 mph as well.

I have checked my trunk for Neanderthals; no dice.

SVX JAZZ · #11 08-25-2006, 11:18 AM

Mine had done something like this for a long time on thw 1-2 shift - always after the car is warmed up. It sounds and feels like riding over the rumble strip on the highway but not as bad. If I let off the gas during the 1-2 shift it isn't bad. I am interested in what you find out.

crotchrocketony · #12 08-26-2006, 11:52 PM

hey guys, I have seen this problem in dodge vans and alot of GMs and it was cured by a trans flush and the fluid replace with the BG syn fluid. most dealerships use BG products and some trans shops. the BG syn. trans fluid is the ****! I have cured alot of trans problems (everything but slipping) by doing a flush with the BG machine and useing the Syn fluid. It is a bit costly around 200-350 depending on how bad the shop you go to bends you over but is well worth it...you wont have to change the fluid for along time after that....it doesnt break down like normal ATF I think BG has a web site...check it out

tony

The Goat · #13 08-27-2006, 06:39 PM

Update:

The shuddering has, over the last couple weeks, subsided to the point where it's barely noticable. I have no idea why. The humming noise is still there, though.

This car freaks me out.

The Goat · #14 01-17-2007, 12:50 PM

UPDATE:

Broken rear driveshaft.

Anyone have an inkling where a brotha can get one cheap?

(or cheaper than the $900 the dealership quoted me before I burst into hysterics?)

ETA it's the U-Joint on the driveshaft itself - which obviously caused an issue with the driveshaft, because I'm an idiot and drove it for so long without getting it diagnosed.

nysvx10 · #15 01-17-2007, 12:57 PM

Ebay had some, keep checking there