Rocky70304

iTrader: (4)

Alright, interesting problem, car runs and performs perfect. except when you get into 5th and 6th gear at low rpms there is horrible vibration will shake the entire car badly. the catch is when you are in 5th and 6th it doesn't do it at steady speeds you have to be givving it gas, and it goes away at higher rpm's.. I really can't come up with a good explanation to explain it , any help, or if anyone has ran accross this problem before please let me know. thanks

CRAZZ28

iTrader: (13)

Is the car stock? What gears do you have? It could be as simple as shifting into 5th or 6th at too low of a speed. It sounds like you are simply lugging the motor down.

Biggin'89

iTrader: (2)

x2 just downshift and don't worry about it. now if your rpms go up fast but speed doesn't change then your clutch is slipping and you do have a problem.

RickyMartinZ28

iTrader: (5)

Mine is a 4L60E and does the exact same thing in high gear... I'm thinking mine could be convertor shudder though...

transamws6_97

iTrader: (5)

same thing would happen to my sunfire when in to low of a gear. basically your just misfiring so its most likely either your wires, plugs, or opti

Rocky70304

iTrader: (4)

well, the misfire scenerio is what I thought at first, but new opti, new plugs, new wires, it doesn't stop shaking the entire car until you are at around 3500 rpm in both gears, rear end gears are factory, clutch has been changed and only has probably 10,000 miles on it, engine is pretty much stock, just some bolt ons, cai, exhaust, etc... It felt like a mount issue at first, so I checked all the mounts along with every bushing on the vehicle and everything feels tight. It used to not do this when I first got the car, but it has gradually starting doing it more and more...?

Paul Bell

iTrader: (9)

I have the same problem with my A4 car, top gear only at highway speeds under moderate throttle. It goes away as soon as I get into it more and it downshifts into third. No problems with motor or trans mounts. I have so many things added, sub frame, rod ended arms & PH bar, rod ended TA, I don't know where to start. Everything looks tight and good.

PLUS, It's so damm cold out, I can only do so much on the car and I'm without a lift.

phirepower

iTrader: (2)

i attribute that problem more to speed, at what speed does the vibrartion occur. I had a similar problem, bought an ls1 driveshaft ... solved

Paul Bell

iTrader: (9)

I don't see how it's the driveshaft as it happens only in certain gears and power levels. As always, I can't rule it out, it can be anything.

I'm still running the stock driveshaft (it's been balanced with new joints), I won't invest in a new one until I go to a new rear. All I need is lots of money.....

Rocky70304

iTrader: (4)

Is it possible or the driveshaft to cause it, only in certain gears and speeds? I am still using the stock driveshaft, i pulled it to check u-joints and they look good at this time.

Ralls

iTrader: (32)

DOWNSHIFT. Your bogging down the car.

Paul Bell

iTrader: (9)

"DOWNSHIFT. Your bogging down the car."

To whom are you speaking? The vibration I'M experiencing is definitely NOT the engine bogging down or lugging.

phirepower

iTrader: (2)

Dude its the driveshaft, unless you are indeed bogging the car. what speed does the vibration occur at, lt1 drive shafts are notorious for being unbalanced, or weighted wrong. At 80mph plus mine would shake and shimmy like you wouldn't believe. u-joint might have worn out, but i'm convinced you have a warped or damaged driveshaft. i don't understand why you are waiting for a new rear to buy a new drive shaft, off ebay or here you can get them for under $120, and it's a good upgrade even if it doesn't totally solve the problem, it will improve the drive quality and acceleration regardless. If you are local you can have my stock drive shaft it was rebalanced and was good till about 115 before it started shaking again.

phirepower

iTrader: (2)

I just reread your first post in this thread, you are indeed lugging the motor

Paul Bell

iTrader: (9)

Hey phirepower, I do appreciate the help and advise. I assure you my friend that my vibration issues are not caused by the engine lugging.

It’s my understanding that when changing from the stock rear end to a 12 bolt, the drive shaft length is different. Also, the U-joints are larger. I know there’s change-over U joints that have the larger size one way and the stock size the other. As the next logical upgrade on my car is the new rear end, I’d hate to buy a drive shaft only to soon have to replace it.


I’d like to cure my vibration issues now as the car is pretty much a daily driver. When I’ll be able to afford the rear end is another story, I’d like to think by summertime but I have to stay optimistic as my business causes me to live job to job, feast or famine, I never know what the weeks ahead hold. Ultimately, my goal is for 475+ RWHP with a block that’s sitting in a machine shop waiting for me to find the money to build it.


I do know one thing. I’ve seen a few posts here and there saying that the aluminum drive shafts are prone to twist and break with good power and good tire hook. I’m gonna make mine a 3 inch steel shaft.


So, I ask you guys who’ve been through this: What is the drive shaft length differences between stock and the Strange 12 bolt rear? Is there a shaft I can get that has the large U-joint in front and the large/small in the rear that'll also fit when I go to the 12 bolt?


Can anybody recommend a maker?


I’m still not totally convinced that my vibration problems are in fact the drive shaft but if I can do the upgrade without tossing money out the window I’ll do it. Hopefully, it fixes the vibration.

moserman

iTrader: (7)

i agree with the driveshaft issue. change over to an LS1 driveshaft and i guarantee your vibration issues will leave. take my advice going through 3 stock lt1 driveshafts. i had the same lugging issue. if you do not think it is a driveshaft issue, then check all O2 sensor wires and plug wires, for you may have melted the wire jacket and caused a short. just throwin my experience with the same problems in there for consideration.

Paul Bell

iTrader: (9)

This thread seems to have died. I'm still hoping for some kind of an intelligent, informed answer from somebody with actual experience. Is there a difference in drive shaft length between using the stock rear end and the GM 12 bolt? I’m sure somebody’s using the 12 bolt and either re-used their shaft or swapped it to a different one.

letsrun97z

iTrader: (7)

i had the same problem when i first bought the car couldnt go really fast mine was about 70mph where it started to do it bad and would ge worse with speed. i took the stock one in to get balanced and put two new u-joints on it and the guy said it balanced out fine with a lil weight and still did it after wards needless to say i bout a DS for an 02 ss on ebay bam problem solved so dont go wasting 100 to balance the old on when you can get one for 150

Paul Bell

iTrader: (9)

Yep. It's established that a later drive shaft will fit. Not the answer I'm looking for. The LT cars and LS cars both have the 10 bolt rear.

Will a F body with a 12 Bolt rear use the same length drive shaft as with the stock rear?