Hi All, What are the options for replacing uni joints on a 91 NA 2+2?, so far I have heard some uhmm quite "high" pricing quoted just to replace the joints, let alone balanced etc, I have read about getting them machined so they take other uni's from a 1 tonner I think it was, but that sounded excessive too, how about 1 piece? also if they are finicky to balance how hard are they to get back in properly?, Thanks in advance guy's!
It's not really practical to change the universals in the OEM two piece tail shaft as they are staked in position & as such are not suitable for reconditioning. Given adequate machining facilities, the yokes could be modified to house replacement uni's, however it's more convenient (& cheaper) to purchase a new one piece tail shaft. Going the one piece route also eliminates the rubber centre bearing that causes vibration when it wears. Even considering the freight charges, importing a new one piece shaft from the US is a viable proposition.
Speaking of tailshafts .. what are the options for steel ones today ?. Destroyed my C/F on the dyno Will get it repaired but need a back up around $680au Delivered with UNI/CV joint from Z1 around $580au Delivered with UNI/UNI joint from Z1 in AUS Delivered to your door ? .
Have a shop around some driveshaft shops, heeeeaps of options and not far from you. For a steel shaft you should be looking at around $600. Why are you looking at steel anyway? If you want something light that can handle big power without worrying about failure you really should be looking at big diameter 'moly tube. The uni/uni version of the Z1 shaft looks like it uses that ally 4 bolt/6 bolt adapter too. Not worth the risk.
getting the Z1 steel with cv joint now off from a member for $450 for now cant see how a big diameter moly is lighter than the steel.
WRONG, don't use a CV joint one pce. If you look AT THE CV JOINT IT CAN MOVE BACK AND FORTH ABOUT 20MM within itself. so under load it actually shifts forward and back and affects the amount of engagement in the back of the gear box as the sliding yoke moves at the same time. Bad idea all around. Last CV joint drive shaft I used, HAD to be shorter than ideal because the CV joint back rim has to be able to engage into the 20mm cup on the diff So you can slide it into place. After it is fitted the engagement length of the yoke in the gear box output shaft was significantly shorter than the 2 pce it replaced. This added to the CV joint sliding back and forth meant you could have up to 30-40mm less yoke engagement on the gear box output shaft. Use a UNI joint drive shaft and the adaptor to get outside of the diff cup. This forces full yoke engagement in the gb output shaft BY default. Get one made local if you want BUT DONT USE A CV JOINT SHAFT ON YOUR CAR WITH ALL THE POWER IT HAS. OR you will be getting a box rebuild to replace the output shaft quite soon.
BTW, I was buying new shafts from Jeff Lagerway in Knoxfield down here for about $350 to $400 with either new Unis from a one tonner or he would reuse your CV joint on the new shaft if it was NOT a big power engine. I only got that done once after I saw the limitations of doing it. Since when is a 4 bolt UNI a risk of breakage? Plenty of big torque cars have used unis for years. Get it made WITH A BIG UNI USING BIG BOLTS. Z1 use that adaptor for a reason, So the yoke doesn't pull any further out of the gear box than it has to. The length of the diff cup flange..........
hey Tekky Gone through researching the last few weeks about the CV . I understand what you are saying but the force is a twisting motion . any front to back movement due to diff/suspension that may occur will be done in place of least resistance which is at the yoke/gearbox which slides easily . The other important question is Z1 has been doing this for years and not one problem against this theory unless you can show me some links? .
Gentlemen Firstly, equivalent thickness material, Chrome-moly steel and plain steel are more or less the same weight. The weght saving alone comes from being able to use a thinner chro-mo wall thickness for the same diameter of tube due to increased strength of chro-mo. However, this weight "saving" comes at a price in the form of fatigue related cracking, especially around the welded joints and catastrophic failure. Changes in molecular structure happen to chro-mo when welded and the areas become brittle and prone to cracking if the welds are not top line. Ally shafts are no better in that for a given diameter the wall thickness needs to be increased dramatically to recover strength. Might be a bit of weight saved in ally yokes....yay! additional flexibility and fatigue related cracking is normal. Composite tailshafts IMHO are an expensive and futile exercise in automotive fabrication and completely/accurately define the term "modification for modifications sake". All in the name of saving weight...like how much exactly? Its not even unsprung weight and the rotating mass at such a small radius...... I mean FFS the gains are incremental at their astronomical best. Cost for cost and fark-about factor balanced out, Id rather have my flywheel lightened at the outer radius to achieve a far better result. Nobody here can say, without their hand firmly around their cocks carrying out a selfie Dutch Rudder, that they achieved any performance increase worthwhile enough... at all really, to offset the loss of structural integrity that is such an important factor of a driveshaft. Hell, one of them here fell apart on a frikken dyno..... dafuq??? Weight saving on a tailshaft is possibly one of, if not the most useless mod (for mods sake) that can be carried out on a car. Even a strict race car when you balance any performance/weight gain against risk of failure. There are NO compelling reasons, performance or mechanically wise to justify fitting anything but a 3" plain steel 1-piece in place of stock when the unis finally wear out. A moly tube in the same wall thickness would probably be the ultimate strengthwise for the given length/diameter of tube but the additional cost/risk of failure around the welded area hardly justifies the decision to use it. Unless its an "impress the tyre kickers" kind of thing. I dont know if its feasible to increase the tube diameter to say 3.5 or even 4" tho. Id wonder if the tube rigidity would lead to, say a front yoke tube failure (the internally splined tube splits around the gearbox output shaft). Twisting shock loads, such as a dropped clutch or wheel hopping from compression lockup, the nefarious practice of wheelspinning from dirt to bitumen et-al have to be dropped somewhere and an extremely rigid driveshaft might drop the shock loads to a weaker point at either end of the setup. Im only speculating/thinking out loud here. Just have a nice and simple 3" plain steel 1-piece shaft made locally or as I did, bought through ShaftMasters from the USA. It cost me well under 400 delivered. It "appeared" well made and it does what its sposed to do albeit with a discernible increase in transmitted transmission noise... meh. My new rear tyres increased road noise more than the tailshaft. E
I understand what you are saying BUT. Ever has a CV apart? The slide grooves are a spiral. The load may be twisting But the CV and slop in the yoke ad up to a major part of the length of the yoke not being engaged with the output shaft especially if you choose to run the CV without the Z1 spacer. If you look at the 2 pce shaft all the lengths in the sections cannot really change because of how its supported regardless of what happens to the suspension or GB position. The spacer has a function beyond the obvious. If you use a CV one pce shaft without it. To get the shaft inside the diff cup you have to slide the shaft forward into the GBox then pull it back into the cup which is about 15-20 deep. That is about the amount you have disengaged the yoke from the box. That slop and the slop in the CV as it is driven and rested ARE A LOT more than 15-20mm. When you are fitting it up you will see what I mean. I bet $10 you pull it out when you see what can happen. have a look how much Yoke is actually not engaged on the GB. If you don't space the shaft out of the diff cup it will be a gnarly amount of disengagment. All the previous Z1 drive shafts have had Uni's NOT CV's. AND I would bet little to none of them have had to transmit 450 RWKW through them. AND then I read Z1 reuse the CV's from old drive shafts in theirs Just like Geoff does. LOL
I have weighed 'moly, and yes thinner wall/thicker tube is the way to go for best weight/strength compromise. There is room to go bigger diameter than what z1/PST/etc use, which gives you room to go full size uni joints. Don't take my word for it go talk to people that build these things ever day for more demanding applications than my car of yours will ever see.
I'm running stock rear cv. Lots of hard launching with t brake and its still going strong. Running ford front obviously. Will go 1350 forged if it grenades but doubt it will. Steel made by phil at final drive.
Personally I agree with both Tekky & Tas, when I go to a one piece it will be plain ordinary steel with big uni joint ends. Hell even Ferrari run plain steel driveshafts. No CF, alloy or CrMo and for all the reasons well covered in this thread.
I have to agree with this. Obviously, I am not running with HUGE power(272RWKW)but I don't creep around like a Nanny either. My car is running a One-piece(modded by Hardy Spicer)and has the CV+Spacer at the rear end. This has been in daily usage for around 9+yrs and has zero signs of wear/deterioration(and NO G/Box problems).:zlove::br:
Sure, but if you want a full size uni you've gotta go up to 3.5", which means chrome moly if you want to keep the weight down. Everything as with any mod is a balancing act and a series of negotiated compromises. Have been through this with people that know a hell of a lot more about it than me, and more than your average mecahnic or shaft builder.... all depends though do you want "good enough for the job" or "isn't going to break for a ****ing third time in a row..."? I realise most people want something that will do the job, but doesn't hurt to put the info out there for those wanting to absoloutely minimise risk of failure.
