Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt

[NickJ]

23 hours ago, mjrstar said:

Shaft is tricky to get good purchase on, but appears snug. It's a 32 spline nissan cd009 gearbox from a 370z.

It's pointing to an outer bush but the parts breakdown I found looks like that's not really a thing it has.

Some garbage google results suggest these gearboxes are OK with radial play up to 1mm.

Ah, so its more of a rocking play than true radial? Nose of the yoke is steady while the UJ end can move? Depending on the ratio of spline engaged and where you are measuring from, 1mm could be expected. How much axial spline engagement is there? Having axial float is needed, 15mm might be at the upper end, closing that up might help with the wobble as long as it doesn't bottom out under extreme travel.

One benefit of involute splines is they self centre under load, negative is it probably flops around off load, from the above is sounds like wear is in the yoke rather than gearbox? While there is a bush in the housing for the OD of the yoke (or it might just be the housing) replacing and machining this tighter is risky as it needs to either have clearance or be concentric to the pressure circle of the spline.

With the Nissan boxes, i've been told that they are fine if the oil seal is intact, not a very scientific assessment of spline wear though! For reference, lip seals usually have 0.5-1 mm radial runout allowance but there are a few other factors involved here too.

Man waffle with no answer, sounds like you've got wear in that area, but its possibly not much out of the normal for that arrangement

[mjrstar]

I have another driveshaft which is too long to fit, but it has no dust shield so I could potentially fit this and get a closer measurement for actual radial play, and see if it varies from the current one. And maybe i can get closer with veriners instead of the dti.

Right up at the output it will be less than 1mm.

I didn't measure engagement but I'd say it's probably something like 70mm maybe a bit more.

There shouldn't be much in the way of axial travel as the diff is solid mounted and the gearbox is very close to solid mounted.

 

I probably should shorten the spare driveshaft,  but it's a bit of a process being carbon fibre.

[smokin'joe]

2 hours ago, NickJ said:

Ah, so its more of a rocking play than true radial? Nose of the yoke is steady while the UJ end can move? Depending on the ratio of spline engaged and where you are measuring from, 1mm could be expected. How much axial spline engagement is there? Having axial float is needed, 15mm might be at the upper end, closing that up might help with the wobble as long as it doesn't bottom out under extreme travel.

One benefit of involute splines is they self centre under load, negative is it probably flops around off load, from the above is sounds like wear is in the yoke rather than gearbox? While there is a bush in the housing for the OD of the yoke (or it might just be the housing) replacing and machining this tighter is risky as it needs to either have clearance or be concentric to the pressure circle of the spline.

With the Nissan boxes, i've been told that they are fine if the oil seal is intact, not a very scientific assessment of spline wear though! For reference, lip seals usually have 0.5-1 mm radial runout allowance but there are a few other factors involved here too.

Man waffle with no answer, sounds like you've got wear in that area, but its possibly not much out of the normal for that arrangement

that coupled with diff backlash makes noise.
with my LC80, there 1M km difference between front and rear diffs, so plenty of catch-up before full drive 

[bigfoot]

Got some cams with an engine I bought in bits, one lobe is a bit ugly looking. Is it fucked or just send it?

[tortron]

Borked

[Sunbeam]

On 02/04/2026 at 16:46, ThePog said:

All this sexy spline talk has reminded me I need to get a custom rear driveshaft made for the truck. It currently has a SWB safari one that I had the joints replaced, balanced etc.

But the thing was secondhand and the splines are not all that, which was noted by the boy at the time.

It works ok with no vibrations even though it sits at a significant angle, but it often makes creaky clunky sounds at low speed, particularly if I have neglected greasing it.

So can anyone recommend an outfit to sort something? I want to go with CV joints rather than UJ or double cardan, and obviously would want a new spline setup and for it all to be chunky as all fuck so I never have to worry about it..

TIA

I hear good things about Circle track engineering in chch. I found them hard to communicate with so I had a driveshaft rebuilt (new slip join spline welded on) by MS Coombes. Did a good job but I thought at $1300 it was a lot of money for what it is. This is nearly 3 years of inflation ago.

[RUNAMUCK]

It's an expensive business. 

I paid something like $360 to have my driveshaft welded and balanced at circle track. (We shortened it in dad's big lathe.

[smokin'joe]

54 minutes ago, RUNAMUCK said:

It's an expensive business. 

I paid something like $360 to have my driveshaft welded and balanced at circle track. (We shortened it in dad's big lathe.

hearing good things bout Justin Neal? Engineering. runs a fast class Mini on the track. seems like a good rooster to talk to as well

 

[RUNAMUCK]

I have met him, (Circa 2004) I don't know if he has the gear to balance them though. 

That said I've run Numerous home.shortened (unbalanced) drive shafts. (At least one to over 200kph)  (with no drive shaft hoops) and I never died.  But LVVT want proof of balancing for cert. (Fair enough, because there's engineers, and there's drunk hillbillies with cheap nasty stick welders (with damp electrodes)  and if you've seen the mess a failure in this area you'd get why....

[smokin'joe]

15 minutes ago, RUNAMUCK said:

I have met him, (Circa 2004) I don't know if he has the gear to balance them though. 

That said I've run Numerous home.shortened (unbalanced) drive shafts. (At least one to over 200kph)  (with no drive shaft hoops) and I never died.  But LVVT want proof of balancing for cert. (Fair enough, because there's engineers, and there's drunk hillbillies with cheap nasty stick welders (with damp electrodes)  and if you've seen the mess a failure in this area you'd get why....

old mate down here. Alan Humphris (bless his soul) never had anything balanced, even under LVVTA/LT400 rules. just prepared the job, set in lathe, and welded to speed. he done hundreds of race car d/shafts with no complaints regarding vibrations........... and yes to the naysayers, real fucken racers who knew balancing(if needed) was 0.1-1 second a lap, proper oldschool clever and fast racers

[gibbon]

I could probably put my prop balancing gear on a driveshaft in situ and run the car up on the hoist if anyone cared that much. not sure if my paperwork is accredited enough though 

[Nominal]

1 hour ago, gibbon said:

I could probably put my prop balancing gear on a driveshaft in situ and run the car up on the hoist if anyone cared that much. not sure if my paperwork is accredited enough though 

Only good enough for planes?

[gibbon]

tbh I wasn't being facetious, there's a lot of very clever guys who aren't certified for aircraft. Likewise I could probably balance a driveshaft pretty well, but no idea if I carry appropriate qualifications for that to transfer to getting signed off in the automotive world. but the offer's there if anyone wants peace of mind!

[RUNAMUCK]

Given I've done 200+ on 100% unbalanced home shortened drive shafts, (granted done by a competent engineer) I'd 100% give you a box to make a home jobbie shaft less unsafe.

 

 

[ThePog]

I have had a fb barry tell me that a cv setup wouldnt work, and I can kindof see it seeing as the cv's would probably move easier than the spline and bind up. Fuck knows really. 

So I probably just want to find a totally primo shaft or weld in the spline section from something new/big/strong into what I have.

[Sunbeam]

 Motorbike electricity question: I have a WR250 that was failing to charge the battery. I followed the instructions in the workshop manual and the stator primary coil failed the resistance test, it was out of spec high. So I bought a new stator from Moto1 (RM branded), fitted it and now I have no spark. So I got the multimeter out again and both the primary coil and  the pickup coil are open circuit. WTF? Do these things have a habit of being DOA?

[h4nd]

Not sure, try the bike spam thread for experts / barries?

 

Oh and this animated page is gloriously nerdy:

https://ciechanow.ski/mechanical-watch/

(ahem @tortron)

[Rookie]

On 15/04/2026 at 06:35, Sunbeam said:

 Motorbike electricity question: I have a WR250 that was failing to charge the battery. I followed the instructions in the workshop manual and the stator primary coil failed the resistance test, it was out of spec high. So I bought a new stator from Moto1 (RM branded), fitted it and now I have no spark. So I got the multimeter out again and both the primary coil and  the pickup coil are open circuit. WTF? Do these things have a habit of being DOA?

I wouldn't say a habit, but it does happen, for example I had a brand new Ricks regulator that output 18.5 volts at idle, so manufafcturing defects do happen. These systems are fairly simple, how much out of range was the original one? Did it output ac voltage on the charging side of the stator?

[Sunbeam]

14 hours ago, Rookie said:

I wouldn't say a habit, but it does happen, for example I had a brand new Ricks regulator that output 18.5 volts at idle, so manufafcturing defects do happen. These systems are fairly simple, how much out of range was the original one? Did it output ac voltage on the charging side of the stator?

Original was 0.6 ohm. Spec is 0.238-0.435. Was putting out volts, just not enough 

[tortron]

Was @h4ndmaking some kind of bit holder recently?