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Driveline angles 81' wagon


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I'm currently investigating weird driveline vibrations in my resto'd wagon, it has the L series 5 speed D/R with a custom single piece tailshaft to the L series rear diff. The main vibe I'm chasing is the one that appears in the rear at highway speeds, around 100 km/h (60mph) and above it gets worse and worse the faster I go. It goes away if I take a rear axle out and the tailshaft no longer spins. Super frustrating because I want to do some longer camping trips but feel like I can't because of this. I got myself a digital angle finder yesterday and tried measuring the driveline angles of the front and rear uni joints on the tailshaft. Has anyone else gone through this process? 

I get different results measuring off of the uni joints (tailshaft installed) compared to measuring directly off of the diff/gearbox with the tailshaft out. In any case there appears to be a difference of 6 degrees between the gearbox output and rear diff input, making the operating angle of the rear uni joint 3.6 degrees approx which is no good. Front is not as bad, around 2 degrees. The gearbox output is pointing down fairly steeply. The front of the rear diff is more flat, needs to come up to match the box. I think I'm only having this issue since I'm running the single piece shaft, most other people AFAIK are using the 2 piece shaft which I think would absorb more of this difference in angles and not vibrate at high speed. Having thought long and hard about going to the 2 piece, I decided to try and fix the issue with the single piece, don't want to pull up my carpet and sound insulation to weld or drill into the floor pan. This car is my daily driver. 

My plan for the fix so far is to slightly shorten the lift blocks that the torsion bar/tube is mounted to and extend/shim the blocks that the moustache bar is mounted to in order to angle the diff some more. Watch this space for results. Changing the gearbox angle is a no-go; shfiter mech binds up before I get even 1 degree of adjustment.

Interested to know if anyone else has run into this issue and if/how they rectified it. 

 

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Edited by Silverbull3t
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perfect opportunity to do a CIG diff Sam. One rear axle out to drive highway, slip it back in for off roading.

while you contemplate the regular two piecer, scour your scrappies and hoarders for the last rear wheel drive Mazda 626 of about 1978 to 1982.

their two piece tailshaft is no good, but the cross member, with some work, will take L Series center bearing and bolts so nice and neat to the flats of the floor of Brumby (so assume wagon the same) so all you see is a factory looking cross member and the bolts go through floor to brackets of choice on the top side. No welding to body to burn insulation and carpet.

Both of my single piece tailshafts made for Crossbred give woes. I never tried removing an axle to see what happened. - probably not good for my LSD . Oh, migh be an LSD for sale in Gippsland coming up if interested

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Should have mentioned, the vibe-free driving with missing rear axles was back when it was an open diff, I've got the Torq locker installed in my wagon now Jonno B) Not sure how it would go with 1 axle missing I imagine it would be ratcheting constantly. Might have to take both axle out and I never could get them in or out without unbolting the bottom of the shock absorber and the 3 bolts to the torsion spring, let the control arm sag as far down as it could possibly go to get enough room to swing the axle in. Not fun on the side of a dirt track. Not keen on grinding my stub axles down either :unsure: 
Rather fix the driveline angles so it's all working as it should be, thinking of a way I might be able to slot the diff hanger bracket for adjustable pinion angle...or an offset hanger bushing maybe? 

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What I did like to read above is that it is your daily driver :)  KNOCK, KNOCK - that must be your local milk authority at the door - wanting their crates back :)

I wonder if you got that natty little gadget onto an L Series two piece shaft to measure up all it's angles to see if something gels. I have done a few L shafts into EA81 and never had problems until I tried to improve on things and go single piece tail shafts.....

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I’m with a very experienced mate atm that knows loads about things like this. 

When did this issue show up and what was changed if anything?

He’s suggesting the following: 
- non-hub centric rims 
- issue with the diff 
- rear CV shaft issue
- locker ratcheting at high speed. Tyre pressures equal on the rear? 

It sounds to us like it’s the rear CV shaft that you’re removing that’s the issue. The torque locker will still rotate the prop shaft with one CV shaft removed, that’s how they operate. 

Don’t go messing with the K frame lift blocks! Just drop the moustache bar if you want to experiment. 

Don’t put in a two piece tailshaft!! LAST RESORT at best…

I’m looking forward to an update. Sorry I didn’t read this earlier, was out on a 4wd trip :banana: 

Cheers 

Bennie

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Copy/pasting across two forums for anyone else reading...

That's a good idea to narrow it down, remove both rear axles and drive it in 4WD. To achieve a similar result I had thought of removing the tailshaft (easier than removing axles) and going for a drive but I don't have anything to plug up the back of the gearbox at present. We're going back 12 months now in the memory bank; when I drove it without the rear axles in (2WD mode) there was no vibration, it only appeared after I put them in, I don't suspect the front axles. 

It happens all the time regardless of on power or coasting, in gear or neutral. Gets worse with more speed, if anything I might say it's slightly worse when coasting. The rear axles are genuine AFAIK I got from a U-pull it wreck then had rebuilt at a good CV shop, they look like new now. Had to beat the ever living hell out of the inner cups to get them off the donor diff, is it possible to deform those? Then again the frequency of the vibration is much higher than wheel RPM so maybe not the CVs. 

-The rims are a nice snug fit on the hubs, I got adapter rings to ensure that. 
-The diff is a possiblity, although the vibe was there with the stock spider gears and no different after the locker went in. Didn't notice anything bad when I had the diff apart. 
-Rear CV shafts, also possible but I had them rebuilt professionally. 
-The locker isn't ratcheting during the vibe, unless I go around a bend then I can here a slow click, click, click which is normal. Tyre pressures are equal. 

I hope we're getting a trip report with piccys of this 4wd trip :)

Edited by Silverbull3t
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On 9/26/2022 at 10:41 PM, el_freddo said:

 

It sounds to us like it’s the rear CV shaft that you’re removing that’s the issue. The torque locker will still rotate the prop shaft with one CV shaft removed, that’s how they operate. 

Don’t go messing with the K frame lift blocks! Just drop the moustache bar if you want to experiment. 

 

i agree it sounds like a cv axle try swaping axles

 

personally i would figure out a way to get the rear cvs in and out easily and weld up a stock diff i ran like that for years

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  • 5 weeks later...

It's been a while since my original post, been busy with life and other things. I have done a couple of things in that time however. 
Swapped the rear axles left to right - made no difference at all to the vibration


Today I removed them completely - the main vibration issue is gone, it's a much smoother ride now the tailshaft isn't spinning. Engaging 4WD with no axles as Bennie suggested, the vibration returned albeit less severe I guess since there's less spinning mass with the axles missing. Disengaging 4WD while on the move and the vibration magically goes away. Side note: don't try and engage 4WD while moving with no rear axles installed; the tailshaft is not spinning but the gearbox is so there is an almightly crashing grinding sound  :unsure:

It was an interesting drive for other reasons too, now I am aware there are many other vibrations and shudders from different places at different times  :banghead:  Most of which I previously attributed to the tailshaft.
For example; 

Low frequency shudder when off the throttle/coasting in 4th or 5th gear at say 80 km/h or above. Shudder goes away when back on the throttle OR pushing the clutch pedal in. 
When the engine is loaded up in 4th or 5th gear e.g WOT but not gaining speed there is another low frequency vibration from the engine. 
Rear wheel bearings are making noise and a slight vibration during sweeping turns at speed. 
Car seems to have a bit more pep now the rear drive parts aren't being spun up. 

I'm really kicking myself I didn't specify to get the engine rotating assembly balanced properly when the engine was rebuilt. This engine makes so much vibration and shakiness, it is not smooth by any stretch of the imagination. Even the idle is incurably lumpy and shaky <_<

In any case, I can work to address the worst vibe which by far was the tailshaft and go from there...

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Sam, I have done a litttle further than yourself at this stage, not chasing anything - from memory :) 

I went as far as removing the tailshaft, so it and the rear diff, mo bar , axles, removed 36 kg and 4WD function too I should add.

I used the front cut of a tail shaft, just rear of the welch plug bung at rear of splined tube. As I am not even a machinist's bum * I set to work to remove unnecessary bulk by bench grinder, so I had a tailshaft end of box plug. I made a crude bracket to bolt across the spare holes in floor either side with a bracket going up, bolt through bracket in same plane as tailshaft normally is and a rubber blank off plug on the end of the bolt. If the box plug, former front yoke started to drift out of the box, the rubber buffer stopped it going any further. I now had a 10 speed FWD. It was fun to drive, nose would pick up on acceleration. Your EA81 twin (exhaust) port would be more lethal than my EA82 twin (intake) port, so watch the power if you try it. 

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Sam, what gearbox mounts are you using in the 5 speed conversion? 

The tailshaft vibration could be a dying uni joint. I assume these are new from the modification of the shaft length and were possibly not greased properly. 

Blue-printing the engine (I’m sure that’s the same term used for balancing an engine) would’ve been quite expensive, and in the end it’s still an EA81 that would have noises and vibrations they probably can’t ever get rid of. Don’t hang on to this, just drive it for what it is and enjoy ;) 

Hopefully you sort this vibration soon! 

Cheers 

Bennie

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I just looked at your pics and you've got an angle problem. Your output/tailshaft shaft angle and pinion angle have to be equal (within 0.5 degree) and offset. Meaning, if your tailshaft is pointed down 6.5 degrees, your pinion has to be pointed up 6.5 degrees in order to cancel out the elliptical rotation of the u-joints. Optimum operational angle is1-3 degrees at the joints. The higher the angle, the more chance for vibration though I've had lifted rigs with angles as high as 10-12 degrees with no issues. There are two exceptions to this rule: A driveline with a double cardan joint on one end or a two piece driveline. So, you have three options: 1) Find a way to shim your pinion nose up (don't forget to add more fluid if you do this) , 2) Get a double cardan installed on the pinion side of your one piece, 3) Put in the factory two piece. A couple other things, is the driveline properly balanced and are the ujoint yokes offset 90 degrees from each other on the driveline ends?

It sounds like you have a secondary vibration somewhere, but your test of pulling both rear axles and running 2WD almost eliminating the vibration points right to the driveline since it would no longer be turning at speed. Since you have a locker, even in 2WD, it's turning at speed.

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gosh, you'd hope that a tailshaft shop did the 90 degree offset between each end !

and skishop, that sounds like a plausible theory, explained well !

and disconnecting rear drive from the tailshaft also takes that torque tightening out. I used to find tailshaft issues always went quieter when the rear drive engaged, adding some torque from the back end. FWD sort of left things a little looser to rattle and vibrate. 

 

off to google a cardan joint .....

Edited by Steptoe's photos
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11 hours ago, el_freddo said:

Sam, what gearbox mounts are you using in the 5 speed conversion? 

The tailshaft vibration could be a dying uni joint. I assume these are new from the modification of the shaft length and were possibly not greased properly. 

Blue-printing the engine (I’m sure that’s the same term used for balancing an engine) would’ve been quite expensive, and in the end it’s still an EA81 that would have noises and vibrations they probably can’t ever get rid of. Don’t hang on to this, just drive it for what it is and enjoy ;) 

Hopefully you sort this vibration soon! 

Cheers 

Bennie

My understanding of "blueprinting" is ensuring everything is to factory specs. Engines used to also be described as balanced and blue printed. My first job got me a little too close to a mechanic who grew up with a very gifted engineer father - late 70s, early 80s , built his own fuel injection system management for under bonnet supercharger. I used to get hotting up technical stuff flying about the shop daily. It was better for me than the mechanic before - I had a calculator fly past the back of my head as I was at the balancer - batteries and bits everywhere as it hit the wall !  He didn't see me there, and apologised :)

Edited by Steptoe's photos
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Jonno, I'm definitely not removing all the 4WD gear and only having 2WD, this whole build was meant to be a 4WD from the start :P 
Bennie, they are stock MY gearbox mounts on the stock MY crossmember. The small metal brackets between the mount and the box had their holes elongated so it would bolt up. Dying uni joint is a possiblility, but unlikely since I had this vibe from the moment I put the rear axles in a year ago. Maybe driving it like this for so long has killed the unis too, joy :wacko: They're not the greasable or rebuildable type. Balancing is a step beyond a normal build I know with added cost, the build wasn't very expensive anyway. This twin port is the most lumpy/bumpy EA81 I've driven, it is an old engine after all that's been rebuilt more than once in its life. Doesn't stop me from enjoying it, it still makes me smile sometimes :D 

skishop, everything you said is everything I suspected about the operating angles etc. Adding a double-cardan to the rear never occurred to me, that could be an easy (if not expensive) way out of the issue. Would also have the car off the road for a week or two which is not ideal as it's my daily driver ;) The shaft was built by the only place in town here that makes tail shafts so I would hope it was done right, it has balancing weights on it and the yokes are 90 degrees apart. 
For experiments sake, I'm back to the idea of reducing the lift block height at the torsion bar mounts to bring the nose of the diff up. Need to get a free minute at work to part off some 40mm long chunks of 50mm dia. aluminium on the lathe. 

All this talk when I could just bash two holes through the floor pan and use the 2 piece shaft :huh:

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some older and wiser dudes say not necessary to pay for tailshaft balancing. They suggest hose clamp pair fitted next to each other and shift the difference between the worm drive body of the clamp closer and further apart each time to see if a difference happens. Not sure if my leg being pulled ... never tried it

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I rang the tailshaft shop during the week, a double-cardan joint is a no-go apparently, too much work to adapt things they don't want to do it <_<
So after I clocked off on Friday at work I jumped on the lathe and knocked out 4 spacer blocks for the torsion tube/rear subframe, 10mm shorter than the ones that were in there. They are a bit small (largest scrap round bar I could find) but I figure they were a quick temporary thing to test my hypothesis, if it works out then I will go to some more effort and make something a bit bigger. It was an easy job to get them in, just did one side at a time. I measured the angle of the pinion drive flange before and after, the difference is about 1 to 1.2 degrees. Lets say the operating angle of the rear uni is now 2.4 to 2.6 degrees. This is with a 5mm shim underneath the moustache bar lift blocks as well, so 15mm difference front to back, 0.6 inches roughly. 

The ride height in the rear is now 10mm lower as well, rear tyres are 10mm closer to the body, which is annoying but I don't think I can put 15mm shim under the moustache bar only or the diff would hang lower than stock! 

Went for a quick drive, no rear axles in place so I drove it in high range. The vibration seems to be gone or at least not noticable with no axles in. What is noticeable however is the howling and whirring noises coming from the rear diff when I'm on the throttle...I think this diff is junk :wacko: Or at least the bearings in it are toast. Couldn't pick it out amongst all the other noises and vibrations before I started this journey. I'll have to get it or another one rebuilt to swap in. There is also the low frequency wobble that happens in 2WD that I wrongly attributed to the tailshaft before, only now it occurs to me I never got a wheel alignment done on this car :excl: It doesn't crab sideways or scrub the tyres so I never put it on the priority list, perhaps that was a mistake :unsure:

So one step forward two steps back...

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Tidy work on the lift blocks Sam! 

If the diff is toast it’s most likely in the pinion shaft bearings. See if you can wiggle the pinion flange up and down at all. 

If you’ve had the pinion flange off it could be an issue of not being torqued properly, from what I understand of r160’s this could effect the bearing much like not properly torquing the rear axle nuts on the MY/L series does. 

What ratio are you running, 3.7 I’d imagine but it could also be a 3.9. I’m hoping a 3.7 for your sake as these are much easier to find than a 3.9!! The Gen1 Liberty is 3.7 and the diff will slot straight into the MY ;);) 

I’m hoping a dying rear diff bearing is the issue, easier to fix and will hopefully allow you to return everything back to the way you had it. 

Get an alignment! Driving a vibration free old school vehicle is awesome!! 

Cheers 

Bennie

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alignment never really causes wobble in (what, you forgot to say)

wheel balance with weights takes out wobble, shudder, vibration at steering wheel

I heard a car media guy on the radio talking about our wonderful pot holes, saying that to hit a pot hole, some wheel weights can fly off, so you need to get a wheel alignment.

I would suggest he was caught short for his advice, and think if you hit a pot hole and lost wheel weights, you need both wheel balance and wheel alignment.

If an auto media adviser got it wrong, not hard for an accomplished machinist to do same :)

You are getting somewhere Sam  

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  • 2 weeks later...

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