Propshaft with CV instead of regular UJ. Who to talk to ?

[carl0s]

I'm about to order my third propshaft, but this time I want the most NVH-free prop possible.

Does anybody know who I could talk to regarding feasibility and price of a single-piece prop with some kind of CV joint at the gearbox end instead of a UJ?

I think I want a GKN PX joint / yoke. I suppose I need to find out if GKN make a PX yoke for the Tremec T56 (28 spline, 1.5" O.D.)

http://www.gkndriveline.com/drivelinecms/opencms/e...


Any ideas?

[Mr2Mike]

carl0s said:

I'm about to order my third propshaft, but this time I want the most NVH-free prop possible.

Does anybody know who I could talk to regarding feasibility and price of a single-piece prop with some kind of CV joint at the gearbox end instead of a UJ?

You either need a CV at both ends, or a UJ at both ends. Mixing a CV and a UJ on the same shaft will lead to more vibration rather than less.

[carl0s]

Are you sure? This guy did OK:

[carl0s]

Here is his post from the v8rx7 forum. The car he got this prop for is a 1970 Pontiac GTO.
http://www.norotors.com/index.php?topic=6399.0

andrewb70 from norotors.com said:

I thought I would post an update for everyone. I measured for the length of the driveshaft and Frank worked with me to get the shaft out to me in the time frame that I needed. I was trying to make an event in Michigan for Father's Day with my son, and Frank delivered.

Here is a picture of the back of the shaft installed on the new Mark Williams billet yoke on my 12 bolt rear end.



This is what the front looks like with the modified slip yoke and CV.



Just another shot.



In short, the driveshaft cured my vibration problem. I road raced the car at Gingerman raceway and also took it on a 4300 mile road trip. It's smooth as glass.

Thanks Frank!

Andrew

[carl0s]

This is a factory 2007 Jeep propshaft:

[anonymous-user]

We use this lot for all our dyno / rig shafting requirements:

http://www.baileymorris.co.uk/

[Mr2Mike]

The output of a universal joint does not turn at a constant velocity when run at an angle. You need a second UJ running at an equal (or equal and opposite) angle to the first in order to cancel the cyclic speed variation that the first one introduces. With a CV at one end, there is nothing to cancel out this speed variation so it's passed straight into the driveline.

The fact that someone found fitting a CV at one end improved the level of vibration tends to suggests there was a problem with their original 2 UJ configuration; it's certainly far from an optimal solution unless the UJ is never operated at an angle (and why would you need one it if wasn't?).

I have seen driveshafts assembled where the phasing of the UJ's is 90 degrees out, which instead of cancelling the speed variation makes it much worse giving horrific vibration. Even if the phasing is correct, having the rear axle nose tilted up or down also means the angles at each end may not cancel, again increasing vibration. Fitting a CV at one end might improve things in these situations, but it's not fixing the underlying problem.

[carl0s]

Hmmm. What you're saying makes sense, but I just want the quietest smoothest prop possible. The gearbox and diff flange are only 0.3 degrees apart in my case. Very nearly parallel. I haven't measured the driveshaft angle itself (height of gearbox output above diff) but it's not large. I have an IRS so the diff never moves.

What are your thoughts on the Jeep propshaft then?

[carl0s]

I suppose having a CV at both ends would suit me, but I think that's asking a lot.

I suppose I just need a propshaft place who will use high quality parts, and balance at high speed.

Bailey Morris have a form on their page for kit car propshafts, and the options on that form sound a bit basic to me. It looks like they will only balance it at 3,000rpm for example. I think I would like a prop balanced at about double that.
Here's the form: http://www.baileymorris.co.uk/pdf/kit_car_single_p...

I really want somewhere where I get a choice of a couple of premium brand flanges & UJs, such as GNK.
I have already emailed D & F, to ask about the CV propshaft, but I guess I may just go for a normal propshaft now, with what you have said Mike, plus the angles involved on my car are miniscule. Alignment doesn't seem to be an issue, the problem is more that I have been supplied a badly balanced, under-sized (2.5") prop with cheap UJs.

[carl0s]

Max_Torque said:

We use this lot for all our dyno / rig shafting requirements:

http://www.baileymorris.co.uk/

Thanks Max. I have commented on BM above. I may ring them. I did have a good search through their very thorough catalogue yesterday.

[anonymous-user]

3000rpm is PLENTY enough to "balance" a prop. The important bit is how accurate you can resolve the out of balance forces at that speed. (i.e a perfectly balanced shaft will have no radial out of balances at any speed, an imperfectly balanced shaft will have forces that increase with rotational velocity. Hence, depending on how sensitive your accelerometer, you need to spin the part fast enough to be able to measure the forces produced. (You need to ask for their spec for balance, not just the speed it is tested at)

[carl0s]

Max_Torque said:

3000rpm is PLENTY enough to "balance" a prop. The important bit is how accurate you can resolve the out of balance forces at that speed. (i.e a perfectly balanced shaft will have no radial out of balances at any speed, an imperfectly balanced shaft will have forces that increase with rotational velocity. Hence, depending on how sensitive your accelerometer, you need to spin the part fast enough to be able to measure the forces produced. (You need to ask for their spec for balance, not just the speed it is tested at)

I'm sure it is if they do a fine job of balancing it, but I'm basically feeling like there's a lot of variance in the quality of work and parts with these shop-made propshafts.

At 3,000rpm prop speed, my car is going about 55mph with the 3.91 diff and 255/40/17 tyres.

My current prop feels fine at 55mph. At 65mph the doors are vibrating themselves to bits.

This prop is one-week old, and the UJ caps weren't pressed in all the way either, or they worked loose through the vibration or something.

[Steve_D]

carl0s said:

.......the UJ caps weren't pressed in all the way either, or they worked loose through the vibration or something.

Where were they in relation to the circlips?
They should be out and sitting against the circlip. Further in would potentially damage the needle rollers.

Steve

[carl0s]

Steve_D said:

Where were they in relation to the circlips?
They should be out and sitting against the circlip. Further in would potentially damage the needle rollers.

Steve

Here's a video. There don't seem to be any circlips on it..
http://www.youtube.com/watch?v=9F1_5xwKuek

I have ordered a new shaft from D & F.

[carl0s]

Hypothetically speaking, let's say you ordered a propshaft from a company on 1st August, spoke on the phone and emailed, and gave card details after confirming price and spec. Say the supplier said "How soon do you need it", and you said "ASAP really because I can't drive above 55mph, but obviously I understand that doing stuff right sometimes takes time, so .."

Let's say, for arguments sake, that the supplier said "We need to machine a blank flange to suit which will take a few days.", on the 1st August, and that it'd be out by the middle of the next week (Wednesday 10th August).

But you heard nothing, you emailed on the Wednesday to say that you'd just hit your credit card limit and although you'd paid the bill in full the day before, it hadn't cleared yet, so if there were any problems taking the money, to please ring for another card number.

but you heard nothing, and then two days later you emailed to say "Card is cleared again now. Any idea of an ETA?", and still heard nothing,

so then a few days later, Monday 15th August, you phoned and spoke to the other chap there who said "Oh no there won't be a problem, let me have a look.. and then came back to say they were waiting on the flange to be machined and would come back to you to let you know what's going on",

but you heard nothing, and another week had gone by,

Would you then think it's time just to go elsewhere, or would you ring up and chase it some more, or just shut up and wait ?

The local propshaft place seemed to get the flange from one of their suppliers within a day or two on the last couple of props ordered.

[stevieturbo]

2 weeks for a custom part, and you're crying already ?

I take it you've never ordered very many custom parts before ? lol

Although I'm curious about one thing. What exactly do you have currently, and why do you think the shaft is causing these vibrations ?
What is the makeup of the shaft, length etc ? Drivetrain, diff ?

Whether CV's or UJ's I see no reason why a properly constructed shaft should suffer any vibration.
Ive a simple steel 2 piece shaft with hardy spicer UJ's and it runs up around 9000rpm and it is vibration free.

[carl0s]

stevieturbo said:

2 weeks for a custom part, and you're crying already ?

I take it you've never ordered very many custom parts before ? lol

Actually I've ordered two of these propshafts before, a year apart, from a local place, and they took how long the supplier said they would take, and the supplier communicated when they said they would, et cetera, et cetera. Took a few days to a week.

It's not two weeks. It's two weeks after when they said it would be, and they don't answer emails, or communicate at all.

stevieturbo said:

Although I'm curious about one thing. What exactly do you have currently, and why do you think the shaft is causing these vibrations ?
What is the makeup of the shaft, length etc ? Drivetrain, diff ?

Whether CV's or UJ's I see no reason why a properly constructed shaft should suffer any vibration.

Well duh. I thought it was obvious that I felt my existing shaft was not properly constructed. Of course a properly constructed shaft will not suffer any vibration, which is why I am trying to get a properly constructed shaft made.

stevieturbo said:

Ive a simple steel 2 piece shaft with hardy spicer UJ's and it runs up around 9000rpm and it is vibration free.

Firstly, it's my understanding that a two piece shaft will always be smoother and have a higher critical speed than a single piece shaft.
I have a single 955mm shaft. You can see it in the video above. I am not an expert in these things but I suspect the hardware on the above shaft is not of comparable quality to GKN/Hardy Spicer.

I'm not about to go through explaining everything again and I'm not looking for help diagnosing the source of my vibration problem. I'm already at the point of (trying to) order a replacement shaft so there's no point me backtracking with another person about the whys and wherefores. Briefly, the current shaft is only 2.5" in diameter, so is somewhat undersized for the existing 450hp and 450ft/lb, which will potentially rise to 550 of each, and it has grease nipples where I would probably prefer OEM-like sealed for life, and came with wobbly u joints as per the above video. The vibration only started after I fitted this shaft. I damaged the previous shaft by repeated removal/reinstallation by punch/hammer (bedded against diff flange).

[stevieturbo]

That sort of power wont trouble a 2.5" steel shaft at all.

Although I'd sooner run conventional UJ's for strength than CV's Unless the CV's are very good quality ones.

[carl0s]

stevieturbo said:

That sort of power wont trouble a 2.5" steel shaft at all.

Although I'd sooner run conventional UJ's for strength than CV's Unless the CV's are very good quality ones.

I'm sure not, but it does seem to be normal to specify 3" tubing with these setups.

[stevieturbo]

Normal LS1 in the US has a 3.5" alloy shaft. Cant say I'd ever trust an alloy shaft though.

Some funny cars with well into 4 figure power levels run a 3" steel shaft.

So yes the norm in the US is 3", probably because it is no more expensive than 2.5" and likely easier to get yokes for the commonly used 1350 joints.

I'm not saying to stick with 2.5", but Ive little doubt it is more than strong enough for even the most abusive setup like drag racing with slicks or something.

And of course larger diameter does offer a higher critical speed, which is good.

Another issue with a CV based shaft, and I'm amazed more shafts with them dont break, ie Skylines use them and have a very weedy looking shaft diameter going into the CV. Is where the shaft itself enters the C, it obviously massively reduces in diameter so it will fit into the splined section of the CV joint. This has to be a weak point.
With conventional UJ's, there is no such weakness other than the UJ itself. But 1350's again are well proven at the highest level. Even ones with grease nipples.