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SOT having some fun with driveshaft balancing


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i am still playing a lot with my balancing jig

i upgraded the motor so now i can spin them up to 5000rpm (very scary), and am now using a laser to aling it all, withing 5 thou (pictures).

i learned a lot of things over the last year of various experimenting on that.

what i have found the most interesting is, among the 20+ DS i am owning: 2002, e21, e36, e46 and E60, not a single one of them is true and centered.

Mainly due to improper assembly, improperly stacked u joints (offset) and whats not...

Balancing requirement is 99% due to this, confirmed by the tedious placement of balancing weight on the "low" spots on all of the DS. All of them.

I fuc*ed up few of them trying to straighten them up, either by cut/weld, force, heat,...(hey i am experiencing so its normal to fuck things up)

i successfully trued one of them within 5 thou (0,005") and surprisingly, or not at all, it requried almost no counter balancing.

On the other hand, i can successfully balance within measurable limits, a DS that is very out and almost bend. BUT, i have found that altough a shaft so un-true can be dead stable and very well balanced, it produces a low humm noise induced in the air by the moving untrue tube (like a speaker cone that moves and produce noise), that can be induced to underbody of the car.

ALL DS have a strong harmonic near 2800-3000 rpm which is about 45-50hz. dead on the @!# noise we can hear and feel when a DS goes wrong.

 

Nothing is perfect someone would say, but i am wondering about BMW driveshaft assembly sources....if its a third party or if its done in factory, or even more, on newer cars, if its balanced on the car.

 

fwiw the front DS on ALL XI cars (BMW) are  not balanced....i am wondering why....and its no wonder that its the ones that fails the first !!! (i have horor stories about destroyed transfer cases,...)

 

This is just experiencing for me, but at then end i will buid a perfect DS for my E60.

 

 

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 not a single one of them is true and centered.

 

Yeah, I have found the same to be true. 

Back when Driveline Service of Portland was

making them for me, they came back VERY close to true,

and with very little weight on them.  Whoever was doing their

machining back in about 2005 was VERY attentive to the centers of everything.

 

It's awesome that you're playing with these- one of these years, I hope to do the same.

Because it's just a few yokes and some tubing, right???

;)

 

t

 

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9 minutes ago, TobyB said:

Back when Driveline Service of Portland was

making them for me, they came back VERY close to true,

and with very little weight on them.  Whoever was doing their

machining back in about 2005 was VERY attentive to the centers of everything.

 

That's good news, considering I found this sticker on my driveline.

 

022.JPG

 

Tom

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cool setup!  and interesting findings.  DLS Portland is the only place i have got DS's from.  E46, E30, and 2002.  zero issues.  of course the 02 one has been abused the most.  7500 rpm engine and  overdrive transmission makes for 8k DS rpm at end of straights in 5th gear.

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A friend used to put two hose clamps on the driveshaft while it was on the car and make tiny adjustments after driving it to remove vibration.  Seemed kinda crazy but it actually worked really well.  I think your way may be more accepted.  🙂

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26 minutes ago, TobyB said:

 

Yeah, I have found the same to be true. 

Back when Driveline Service of Portland was

making them for me, they came back VERY close to true,

and with very little weight on them.  Whoever was doing their

machining back in about 2005 was VERY attentive to the centers of everything.

 

It's awesome that you're playing with these- one of these years, I hope to do the same.

Because it's just a few yokes and some tubing, right???

;)

 

t

 

well to be honnest, my saga with the DS started it all because of Driveline "specialist" of portland....i owned back then a 1992 E36 with a bad DS. i bought them a rebuilded one and guess what, it was worse than the one with a dead u joint. so i bought the vibration analyser and a huge AC motor, driving the rear wheels. the motor had to be connected directly into the house fuse box. lights was diming in the house when i started it all. i balanced the DS from under the car at speed.

then sure enough i poked them and asked wtf ? i never ever had a chance of a solution from them.

then i told myself that i could do it....its been like 12 years since that.

i balanced several DS with very good results since then

My E60 is something else....this car is so sensitive to anything....the ds is giving me issues and since is a XI car its even worse.

 

 

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36 minutes ago, '76mintgrün'02 said:

 

That's good news, considering I found this sticker on my driveline.

 

022.JPG

 

Tom

i see but i am very concerned about the amount of balancing weights beign put on it....this is a lot believe me. its like when having #4 of balancing weights on a tire rim....yeah its fine but....

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44 minutes ago, Glen Karr said:

Pat,

Many years ago I used that same IRD analyzer to balance steam turbines for Duke Energy.  Nice to see you are still getting use out of it.

Best regards,

Glen

great so you know how to use them as well ? would you share a bit of info about it ?

its a very nice machine altough very antique by today standards. but rock solid and reliable. no software to fail.

i am also looking at a 2nd transducer...thoses are not easy to find for cheap, it gos from 500 to 2000$ easy alone.

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Hmmm- maybe I got the 'good' guy- I WAS a big pain in the ass with

all sorts of odd stuff, like, metric one end and SAE the other,

no slip joint, etc...

 

...but they were also the ones who encouraged me to 

'stick it in the lathe and try it- as long as you don't score up

the slugs, it's not going to make our job any harder!'

 

t

 

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6 hours ago, TobyB said:

Hmmm- maybe I got the 'good' guy- I WAS a big pain in the ass with

all sorts of odd stuff, like, metric one end and SAE the other,

no slip joint, etc...

 

...but they were also the ones who encouraged me to 

'stick it in the lathe and try it- as long as you don't score up

the slugs, it's not going to make our job any harder!'

 

t

 

i think i am very very not lucky with this kind of things. i got screwed many times with bad DS rebuilds/balancing hence the reason why i do all i can to learn how to do it myself.

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