Driveshaft balancing

[freedom_in_4low]

If you had a local shop lengthen a driveshaft and made it clear that it needed to be well balanced due to the speed it ran, and after installing it you had vibrations starting at 65 that intensify at least through 75, would you even mess around with the shop or would you just send it to Tom wood's (the original builder) and have them do their magic?

Background is I had 10" added to my TW shaft to use it on my LJ. Got the LJ above 50 for the first time yesterday and have a pulsing vibration from the rear end. It's definitely not at tire balance speed, and it feels different (more audible but less felt) than when I've had operating angle issues. It doesn't change based on accel/decel/neutral or disengaged clutch, and there is no front driveshaft installed. 6 speed with 4.88 gears, and for the time being 32" tires which means at 75mph the engine is around 3400rpm and the driveshaft should be around 4k. When I get to 35s it should help some but if it's going on at 65 now it'll still start before 75 with the bigger tires.

 

[Hopper]

I would take it to the shop and see if they are willing to work with you. If not I would go to Tom Woods and explain your situation.

 

[freedom_in_4low]

I would take it to the shop and see if they are willing to work with you. If not I would go to Tom Woods and explain your situation.

Fair enough.

When I dropped it off I asked how fast they balanced up to, he said usually 2300 rpm, but their equipment could do 3300. I explained that I was gonna be running 3500 or better and needed it balanced to as high rpm as possible.

Now that I've done a little reading, I realize I should have been talking in Oz-in instead of rpm, because an Oz-in at 2000rpm is an Oz-in at 4000, but it exerts 4x the force with doubling the speed. So hopefully their equipment has the precision to cut their usual Oz-in tolerance in half and that will take care of it. My reservation is simply that I assume of anyone that they do the best job they're capable of, and being a bit of a hole in the wall looking place in a rough area I don't know what kind of budget they have available for state if the art equipment. I've worked for mom and pop shops before, so I get it. Hell, I've dealt with keeping aging machinery going for a $13B company.

If it works out, it'll at least save me some shipping time and money even if it means a 40 mile round trip to the shop vs 6 miles to the ups store.

 

[Hopper]

I would take it to the shop and see if they are willing to work with you. If not I would go to Tom Woods and explain your situation.

 

[Hopper]

Well you didnt mention all those reservations before maybee a quick phone call to feel em out and ask if their equipment can handle the job. If you dont feel like they can handle it, I would be all about sending it to Woods at least it would be done properly.
Good Luck

 

[Claytone]

If you’re willing to drive a ways, call Bills in Englewood and see what they say. When I worked for Benz, we sent all the DS work to them.
I had my front balanced by them last week. It ended up out of balance after I rebuilt it with greasable joints.

 

[Goatman]

Pull the shaft and put the front in. Drive it to confirm it's the back shaft. Then you can have a more convincing argument if they try to avoid rebalancing their own work.

 

[tworley]

Another vote for Bills in Englewood. They built my previous dc shaft. They also use spicer parts. I had them extend it several years later. My only complaint was cost, they area a bit higher than TW. A year ago I asked to have the centering stud replaced due to damage and the cost to have it done was just shy of a new TW shaft, plus the turn around was a week at the time. So I went with TW and his 2 or 3 day delivery, otherwise I would have used them again just because it is local.

 

[Blackjack]

Fair enough.

When I dropped it off I asked how fast they balanced up to, he said usually 2300 rpm, but their equipment could do 3300. I explained that I was gonna be running 3500 or better and needed it balanced to as high rpm as possible.

Now that I've done a little reading, I realize I should have been talking in Oz-in instead of rpm, because an Oz-in at 2000rpm is an Oz-in at 4000, but it exerts 4x the force with doubling the speed. So hopefully their equipment has the precision to cut their usual Oz-in tolerance in half and that will take care of it. My reservation is simply that I assume of anyone that they do the best job they're capable of, and being a bit of a hole in the wall looking place in a rough area I don't know what kind of budget they have available for state if the art equipment. I've worked for mom and pop shops before, so I get it. Hell, I've dealt with keeping aging machinery going for a $13B company.

If it works out, it'll at least save me some shipping time and money even if it means a 40 mile round trip to the shop vs 6 miles to the ups store.

Most driveshaft balancers measure balance runout at RPM not weight. So you will want to ask what the indicator deflection is they are shooting for and at what RPM.

 

[Rubicon John]

I had an 83 Cutlass with a 383 in it that I swapped a Grand National axle into. It had a different housing and the driveshaft had to be shortened or lengthened an inch. I can’t remember, it’s been awhile. Anyway the shop I took it to claimed “driveshafts don’t have to be balanced” so I think it’s a thought process among certain shops.

I didn’t have any issues with it but it was just a weekend cruiser. As we all know, Jeep shafts need to be balanced. If you run into a guy like mine, he probably won’t be the best Jeep driveline guy.

 

[Blackjack]

I had an 83 Cutlass with a 383 in it that I swapped a Grand National axle into. It had a different housing and the driveshaft had to be shortened or lengthened an inch. I can’t remember, it’s been awhile. Anyway the shop I took it to claimed “driveshafts don’t have to be balanced” so I think it’s a thought process among certain shops.

I didn’t have any issues with it but it was just a weekend cruiser. As we all know, Jeep shafts need to be balanced. If you run into a guy like mine, he probably won’t be the best Jeep driveline guy.

A lot of old time driveline guys were of the mindset that if the shaft is straight enough they did not need to balance it. There was some merit in it as the quality of the parts used used to be of a higher qc standard and the typical RPMs most vehicles operated in were lower. That is certainly not the case now as RPMs are higher, operating angles are more severe, and even the best brands components are not of the same standard they used to be.

 

[Rubicon John]

A lot of old time driveline guys were of the mindset that if the shaft is straight enough they did not need to balance it. There was some merit in it as the quality of the parts used used to be of a higher qc standard and the typical RPMs most vehicles operated in were lower. That is certainly not the case now as RPMs are higher, operating angles are more severe, and even the best brands components are not of the same standard they used to be.

Thanks for the info!

 

[freedom_in_4low]

Pull the shaft and put the front in. Drive it to confirm it's the back shaft. Then you can have a more convincing argument if they try to avoid rebalancing their own work.

I still haven't gotten around to this but now I'm questioning if it's really even the driveshaft. All my bearings are fairly new but it sounds a feels more like tire or wheel bearing noise and it's so mild I'm not even sure I'd pick it up over a louder set of mud terrains or cupped tires nearing the end of use. I jumped at the driveshaft initially because it's the only thing that changed, but I can't rule out that the LJ tub might just transmit more tire noise or maybe the two JJs I swapped in to replace worn out RC flex joints conducts it differently.

 

[Head Lice]

At speed on a long highway curve, does the vibration start, get worse, finally fade away . . . only to repeat on the next long curve?
This will happen if two or more wheels aren't trued. They come in and out of phase. A backyard driveshaft balance can be done with large hose clamps. Time consuming, but cheap.