Just got it rebuilt to fix what seemed to be a bad/noisy input shaft bearing, which I have read is a fairly common failure in these cars due. It turned out that most bearings in the there were bad to some degree. My car has only 123k on it.


I have always seen this issue blamed on defective parts, the bearings themselves being originally manufactured with defects that caused them to fail prematurely.

However, the mechanic who did my work has a different idea. He says these bearings are a high-quality brand that should never fail like this, much less many at the same time.

Instead he thinks that a bad ground connection could be to blame. This would be because of electricity arching and passing through the bearings themselves going between the engine and transmission. This would make sense because the input shaft bearing is most severely affected.

I just wanted to put this explanation out there as it seems plausible. I will be checking my ground strap asap so I don't ruin the new ones.

 

Thanks for the info. The ground is something to check for us 5 MT owners. It won't hurt to be safe.

 

And with that, it appears a critical blow has been landed in the infamous "sanding transmission mating surface is required vs. not required" debate. In all seriousness that is a very interesting theory although I have zero credibility to speak on such matters. Really cant hurt to add a cable or two just in case.

 

I had never heard of this phenomena either, and not sure how well known it is for destroying transmissions.

It's really a shame that something so simple and stupid could cause so much damage and expense, if that is what happened.

 

It's known for causing hard/no starts after having the engine and trans apart if you forgot to sand the mating surfaces.

This seems like a stretch to me and if it were true you can't be the first person with any manual trans car it's happened to or figured it out. I think it's more likely something was in there at some point that tore it all to shreds, I just recently found a broken apart reverse light sensor (round goes in lower drivers side) in my trans, which includes a solid metal ball probably 2cm in diameter. Thing could of destroyed my trans and it's been in there since I bought the car

 

I have heard about this kind of damage if the engine is not grounded properly.

All of the electric power going into the engine needs to return to the battery somehow. If there is no ground wire, the electricity will seek another path.

The engine and transmission mounts are rubber.
The rubber acts as an electrical insulation.
The only remaining path would be though the output shafts.

Imagine what happens as we start the car if there is no proper ground. All the electrical power would ground through the bearings. They would experience arc welding. Sure, the small weld would break as soon as the car starts moving. But the roughness would still be there, and tear up the bearings.

 

Your explanation makes sense but if his grounds were that bad wouldn't he of suffered other symptoms like no start? I just couldn't find any results for this when I tried googling it earlier

 

It turns out I did have a grounding problem.

I measured current flow of 30mA from block to battery negative at idle, and resistance of 2.4 ohms between these points.

Compare this to exactly 0mA and 0.0 ohms respectively after cleaning the ground strap connections.


I guess this ground wasn't super bad or I would have had obvious problems like you mention. I have had a number of electrical issues actually, including random no crank, but these have always been resolved by other means and have not occurred recently.

 

Ok, bad ground.

You did not measure the much larger amount of current the starter would draw. The only major effective ground would be though the transmission output bearings.

 

Very interesting, Ive always heard that our Maxima's didn't have the best grounds, which is why there's quite a few members that claim they've benefited from a grounding kit, or "the big 3 upgrade".

Would never hurt to sand down and check all grounding points on cars that are 20 plus years old.

Ive heard guys say after adding grounding kits, their windows rolled down faster and if you have a high end sound system, it would eliminate dimming of interior lighting when base would hit hard. .