Dyno and u-joint replacement advice

[jkelly]

Hey guys,

 

So I'm getting ready for a trip to the dyno after my fresh rebuild and Megasquirt MS3X install. The engine is all fresh and I've barely driven it. One thing I didn't do is replace the original halfshaft and driveshaft u-joints.  I have some new NAPA UJ393s for the halfshafts and NAPA P391s for the driveshaft that I plan to put in before the dyno run.

 

My question is, would it be better to order the heavy duty u-joints from MSA or will the NAPA u-joints be fine? Differential is the original R180. Planning to make around 300HP this first round.

 

Link to heavy duty joints. It looks like they have more meet around the trunion compared to the NAPA ones.

https://www.thezstore.com/page/TZS/PROD/22-3004

Heavy duty:

 

NAPA:

 

Edited June 25, 2020 by jkelly

[NewZed]

The Nissan u-joints are of very high quality.  $80 each, with precision clips to ensure an exact fit.  If they're not dried up or rusty, why replace them with $20 u-joints?

 

The R180 will probably blow before the u-joints.

[jhm]

I agree with NewZed...if your stock driveshaft u-joints are in good shape, just leave them alone.  If they eventually do need to be replaced, I'd consider Spicer u-joints.  Have worked well for many folks here.

 

Similarly, the stock half-shafts are quite stout; and can handle quite a lot of abuse.  

 

There are other components that will fail first....diff carrier gears, outer stub axles, etc.

[jkelly]

10 hours ago, NewZed said:

The Nissan u-joints are of very high quality.  $80 each, with precision clips to ensure an exact fit.  If they're not dried up or rusty, why replace them with $20 u-joints?

 

The R180 will probably blow before the u-joints.

 

4 minutes ago, jhm said:

I agree with NewZed...if your stock driveshaft u-joints are in good shape, just leave them alone.  If they eventually do need to be replaced, I'd consider Spicer u-joints.  Have worked well for many folks here.

 

Similarly, the stock half-shafts are quite stout; and can handle quite a lot of abuse.  

 

There are other components that will fail first....diff carrier gears, outer stub axles, etc.

 

Great. Thanks for the feedback -- I appreciate it.

 

Do you have any data points on at what torque the outer stub axles and/or diff carrier gears start to fail? There are of course a lot of other variables like the condition of the splines and gears, but I'm just curious so I can have a "do not exceed" number for the dyno tuner. 

Edited June 25, 2020 by jkelly

[jhm]

9 minutes ago, jkelly said:

Do you have any data points on at what torque the outer stub axles and/or diff carrier gears start to fail? There are of course a lot of other variables like the condition of the splines and gears, but I'm just curious so I can have a "do not exceed" number for the dyno tuner. 

 

Unfortunately, I don't think there's a single definitive way to answer that.  It all depends on a variety of factors....how you plan to use the car, what transmission you're using, what tire/wheel combo you're running, condition of your current internal hardware, etc.  Auto trans are usually kinder to the drivetrain than manual trans.  Lighter cars can have less drivetrain failures than heavier cars.  Big tires can impart more abuse on drivetrain components than small tires.  (IINM, open diffs can have more failures than LSDs; but that may not really be a good apples-to-apples comparison.) 

 

I've broken my diff carrier with a very mild SBC motor, but was running tight auto-x courses on sticky slicks.  Haven't had to replace my stub axles yet, but have seen many fail with bigg'ish hp/torque and multiple hard launches on big tires.  This seems to be the common theme with failed stubs. 

 

Is this primarily a race car or street car?  I'd say let that factor guide your decisions, and upgrade/replace components as it becomes necessary.  300 HP (with similar torque numbers) can move your car along quite well for most applications.  Beefier components are readily available; it just takes money.  The R200 is a popular upgrade to the R180, and stronger stub axles are available from several vendors.

 

Good luck with it.

[jkelly]

41 minutes ago, jhm said:

 

Unfortunately, I don't think there's a single definitive way to answer that.  It all depends on a variety of factors....how you plan to use the car, what transmission you're using, what tire/wheel combo you're running, condition of your current internal hardware, etc.  Auto trans are usually kinder to the drivetrain than manual trans.  Lighter cars can have less drivetrain failures than heavier cars.  Big tires can impart more abuse on drivetrain components than small tires.  (IINM, open diffs can have more failures than LSDs; but that may not really be a good apples-to-apples comparison.) 

 

I've broken my diff carrier with a very mild SBC motor, but was running tight auto-x courses on sticky slicks.  Haven't had to replace my stub axles yet, but have seen many fail with bigg'ish hp/torque and multiple hard launches on big tires.  This seems to be the common theme with failed stubs. 

 

Is this primarily a race car or street car?  I'd say let that factor guide your decisions, and upgrade/replace components as it becomes necessary.  300 HP (with similar torque numbers) can move your car along quite well for most applications.  Beefier components are readily available; it just takes money.  The R200 is a popular upgrade to the R180, and stronger stub axles are available from several vendors.

 

Good luck with it.

That all makes sense to me. It's primarily a street car and weekend cruiser, so I don't plan to make huge HP and torque. The tires are close to stock as well. 

 

Thanks! Maybe I'll report back with some dyno numbers in a week or two. 

[NewZed]

The u-joints can all be lubed.  They might not have a Zerk fitting but they should have the hole with a slotted plug in it.  Take the plug out, put a Zerk in, fill them up, and put the plug back in.  Inspect the seals and seams closely for rust or looseness.  If you do find a bad one, just replace the one.  I found that the new aftermarket joints were looser than old Nissan joints. 

[jhm]

I think you'll probably be fine with that setup. 

 

If you'd like to upgrade diff to LSD, an STi R180 is an easy bolt-in.  Good info here on the various Subaru LSDs:  https://forums.nasioc.com/forums/showthread.php?t=2597453

[jkelly]

On 6/25/2020 at 9:22 AM, NewZed said:

The u-joints can all be lubed.  They might not have a Zerk fitting but they should have the hole with a slotted plug in it.  Take the plug out, put a Zerk in, fill them up, and put the plug back in.  Inspect the seals and seams closely for rust or looseness.  If you do find a bad one, just replace the one.  I found that the new aftermarket joints were looser than old Nissan joints. 

I took a look and didn't see the plugs in the current u-joints. Not sure if they had different ones that did have the plug. These are labeled Koyo.

[NewZed]

Sometimes they're hard to see, especially if they're covered in greasy dirt.  The plug has a thin head with a slot for a screwdriver.

 

Should be here.  This picture shows the hole still open.

 

[bradyzq]

It sounds to me as if you expect the dyno to be hard on the driveline. It shouldn't be. There will be no shock loading or wind-up. The only part that might complain, because it's stuck in the middle so to speak, is the clutch.

 

If there are currently  no hints of imminent driveline failure, I agree with NewZed on treating the ujoints to fresh grease. Also applies to the transmission and diff. I like Redline MT90 for the transmission, and Redline 75W90 GL5 oil for the diff. 

[jkelly]

7 hours ago, bradyzq said:

It sounds to me as if you expect the dyno to be hard on the driveline. It shouldn't be. There will be no shock loading or wind-up. The only part that might complain, because it's stuck in the middle so to speak, is the clutch.

 

If there are currently  no hints of imminent driveline failure, I agree with NewZed on treating the ujoints to fresh grease. Also applies to the transmission and diff. I like Redline MT90 for the transmission, and Redline 75W90 GL5 oil for the diff. 

 

I added fresh Redline MT90 and diff oil to the transmission and diff, but the ujoints oddly do not have a place to add grease or take out a plug. The part number on them is Koyo KC1819D. Is that the stock part? Here is a video of one of them: