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Icarus
10-09-2009, 02:10 AM
How can I tell if a vibration is coming from the driveshaft or the diff on a car?

New 4" driveshaft installed. All parts in gear swap to 4.30s are brand new.
I've tried indexing the shaft and it made a little difference. Field balanced the shaft with washers on the rear bolts and it helped the most. Still not totally smooth though. It's at higher speeds that I don't drive at most of the time so hard to tell... I'm stumped as the washers on the rear flange made the biggest difference. I think the diff makes noise on decel, but the installers don't.

I've had the guys that did the gear install take it for a drive and they think it's the driveshaft, and the guys that did the driveshaft think it's the flange on the diff when they built it, so I really don't know!?!

specops_SC
10-09-2009, 04:57 AM
If you have access to another driveshaft, swap it out and see if the vibe is still there. If it is, try another pumpkin. Swap them both if you need to. I'm sure someone around you has spares. That will be the best way of eliminating what is causing the vibration. I havent had a problem like this before so I cant say for sure. Maybe someone else has a better idea. For now, you're going to have to troubleshoot.

Moses

Icarus
10-09-2009, 05:05 AM
It was there with the stock driveshaft and new gears, but not with the stock gears and shaft. Thats why I went with the 4" shaft. It is a lot better now with the bigger shaft, but still there, even after doing all the stuff I mentioned in the first post...
I don't have another pumpkin to try unfortunatley, and finding one up here with the same or similar gears would be even harder. I really don't know anybody around here, another part of the reason I want to try to figure out if it's the driveshaft or diff so I can get it resolved with the ones that I got the ds from, or the ones that did the gear install... :(

specops_SC
10-09-2009, 05:29 AM
The gear ratio in the pumpkin wont matter if all you're doing is hunting the source of the vibe. But from what you just said, it seems pretty likely its something in the diff. If you can isolate the vib to the diff, I dont see why the builders would refuse to inspect it for you. If you want to find someone that can help you out, posting on here is your best bet. Good luck and if you do find out what was vibing, let us know.

Moses

Icarus
10-09-2009, 05:48 AM
Neither place seems to want to help other than to say that it's the other ones parts/install. The place the did the gears took it for a drive and even though it made noise said the diff was fine. I'd have to take a couple hour drive each way to have the driveshaft place look at it. Thats why I was hoping to figure it out myself and then take my findings to either. It's to the point I don't like driving the car any more as I don't like chasing down problems and then be put off to another saying its not us. I went through all this with my alternator and even paid the dealer for a couple hours to tell me what I already knew, the alt was junk. At least it is easy to change unlike anything underneath the car :(
It's not bad now, I should sell the car and buy some new cheap crap one that I least can pawn off on the dealer for a while till it's out of warranty, lol...
Thanks for the suggestions, I'll see what I can figure out and let you know :)

coolhand
10-09-2009, 09:58 AM
Not sure where you are in ONTARIO, but post your problem on the Ont forum, and I am sure you will get some help. Lot of folks up here have a lot of spare parts laying around.

CoolHand

decipha
10-09-2009, 12:01 PM
jack the back of the car off the ground and spin her on up

This will tell you if its a reciprocating imbalance from suspension deflection caused by a worn bushing or such. Which will do the exact same type of vibe as if your driveshaft wasnt bolted to the diff tight.

anyway, if the car vibes you need to crawl under there and check things out, if it doesn't vibe then you know you have something going on with the suspension or tires.

decipha
10-09-2009, 12:02 PM
oh yeah forgot to mention

check your trans mount, if the rubber looks suspect get a new one and never put a solid mount there.

slowpoke
10-09-2009, 12:21 PM
How can I tell if a vibration is coming from the driveshaft or the diff on a car?

New 4" driveshaft installed. All parts in gear swap to 4.30s are brand new.
I've tried indexing the shaft and it made a little difference. Field balanced the shaft with washers on the rear bolts and it helped the most. Still not totally smooth though. It's at higher speeds that I don't drive at most of the time so hard to tell... I'm stumped as the washers on the rear flange made the biggest difference. I think the diff makes noise on decel, but the installers don't.

I've had the guys that did the gear install take it for a drive and they think it's the driveshaft, and the guys that did the driveshaft think it's the flange on the diff when they built it, so I really don't know!?!

did you get the drive shaft balanced? if not get that done. its cheap and fast to do at most machine shops.

Hock
10-09-2009, 04:27 PM
did you get the drive shaft balanced? if not get that done. its cheap and fast to do at most machine shops.

What he said.

Also, searching to find my own high speed vibration (at 65+ mph) the conclusion the I came up with is that it might be the axle bearings that are bad. I have excessive movement in the axle at the center section and its not the inner CV's. SO, my next step is to take the cover off and see if the diff. moves, which mean the diff. bearings are bad or if its the axle bearings.

David Neibert
10-09-2009, 05:01 PM
Wouldn't be suprised to find that the 4" drive shaft is rubbing against something. It's an extremly tight fit and if your diff or trans mount bushings are worn, the shaft is probably hitting something. BTW, a 3.5" shaft is plenty strong for the rpms these motors are capable of turning.

David

Icarus
10-10-2009, 03:43 AM
The 4" shaft isn't rubbing anywhere. I've checked that a couple times now. It was supposed to be high speed balanced at the place I got it from.
Last time I checked it, the pumpkin was in there solid, no play in any mounts. I do have an Atomic Performance girdle/cover on the diff.
I didn't think I could spin the car up on stands... Well I guess I could if I put 'em under the rear arms.

This sucks right now as I just had some surgury last week and won't be able to get under the car for a while (hopefully before the snow comes and it goes to storage!) This is what happens when your stuck inside all day with nothing to do, lol... ;)

Flex
10-20-2009, 12:34 AM
What did you have done?

Icarus
10-20-2009, 12:41 AM
Gears and driveshaft. See my first post ;)

Flex
10-20-2009, 12:23 PM
No, I meant surgery wise.

MartianBob
10-20-2009, 12:44 PM
If it's purely speed dependent then it could be:
bad wheel bearing/hub,
hub nut has come backed off a bit.

I have a tough time getting the rear hub nuts tight enough on my 5 speed. Even with the car in gear and standing on the brakes.

Don't see how it could be the shaft if it's not rpm related.

hope you figure it out.
Bob

Flex
10-20-2009, 12:52 PM
I have the same thought. I have a vibration in mine but only at about 70 mph when you let off and coast. I have not had time to look at it as I just got the car back on the road. I will check the bearings.

KMT
10-20-2009, 03:47 PM
Icarus>How can I tell if a vibration is coming from the driveshaft or the diff on a car?

If it is the driveline, you should perhaps feel vibration in the seat of your pants. Make sure you're not sitting on a cell phone...

From what I recall here, the usual culprits are loose bolts on the driveline flanges and/or simply worn out u-joints. Easy to check once you can get under the car - I would start there.

Icarus
10-20-2009, 04:53 PM
No, I meant surgery wise.
Open hernia surgery. Its been brutal sitting around doing so little, and it's not healing fast enough for me either which means I'll probably be like this for a few more weeks :(

As for the car, I don't think it's rpm dependant as it will do it in 3rd or OD. I'll have to go for a spin soon and see exactly when it's doing it as I can't recall off the top of my head. It was at about 120-125kph though it started, mainly when coasting or decel somewhat too... I'm pretty sure it's not the driveshaft or pumpkin, as it's done this throughout three pumpkins and two driveshafts.