Driveshaft carrier bearing fun.

[HRH]

So the old rubber on the 138k new D21 was crappy, so about two weeks ago I yanked off the driveshaft and replaced the carrier bearing. Got a really nice quality Altrom unit through work, Japanese part, all was good.

 

Had a bitch of a time getting the old one off, finally got enough wood things built up to make a stand since the supports on my harbor freight press aren't wide enough in between to allow the driveshaft to sit on the carrier bearing.

 

Anyway, after pressing off, I looked at the splined yoke, saw that it should butt right up to the bearing face, and the driveflange had the same deal. So I thought, okay, it should press on by using the impact gun on the nut and sucking the yoke down.

 

This worked just fine, though the torque spec I looked up was some ungodly amount, and instead of just checking first, I gunned it on until it seated, and then rattled it a bit more. This proved a problem as the bearing was no longer free spinning. It was rather hard to turn. So I dicked with it some more and figured maybe it would work in and reinstalled.

 

Fast forward to today with the results of 14.7ish mpg for the last tank of gas. In a 4 cylinder KA extended cab 4x4. This is with me babying the crap out of it. Not good. Loosened the carrier bearing collar and spun, and yeah, still not turning so well.

 

My thought is the extra drag is like a little miniature brake on my driveshaft, and that's what is probably contributing to my extra shitty mileage. I mean, 20 mpg in a 4 cyl, 30x9.50 4x4 is okay. I can handle that if I'm abusing her. But 14.7? WTF? Did someone stick a Titan V8 in there?

 

As far as putting the carrier bearing back on, I'm going to be much more careful with the new bearing I have this time, even though logically if the inner bearing race butts up against two solid points, there shouldn't be any ability to bind the bearing. Obviously something is amiss.

 

What say you other ratsuners who have put on carrier bearings? Any tips, tricks I'm missing? My Datsun guru actually chucks the shaft in the lathe and gets it so the bearing will slip on. Says it's a lot easier to get on and off, and his 380,000 mile 720 hasn't had any problems. Unfortunately I don't have a lathe and I want to do it tonight. Was thinking about working it with a little bit of 80 grit, don't know how time consuming that will be though.

[VoidDragon]

Not sure what might have happened to yours, But I just replaced the carrier bearing on my 620.

 

Had to redneck-up a press using crowbars, jackstands, and an air hammer.

 

But it worked.

[athoose]

When I did mine I was given a bearing that was too thick by a slight amount. When I tightened it down to spec it smashed it to where it wouldn't turn. Thats when I took it off and did some measuring. Next one I got, from a different supplier, was just fine.

[HRH]

Hmm, I'm beginning to wonder now. I just sanded down the shaft so the bearing slides on, and it seems it would be able to turn too far. After taking off the bearing I just put on and looking for signs of failure, the rubber cover that covers the metal shield had been sheered off, whereas on the original bearing, both covers looked fine and I'm pretty sure they're not supposed to touch!

 

This is horseshit! I'm going to try and put on the original bearing. Hard to measure the inside, but I'm wondering if they got a spec wrong, because I seem to be running into that. Good quality Japanese bearing though, looks almost exactly like the oe one I pulled out.

[HRH]

Sure as shit, the bearing is wrong. It's a nice quality Tezuka, made in Japan, almost identical, but WRONG! Slapped the old bearing on, no bind, just nice free spin. So I will be defecting out one tomorrow and returning the one I just bought. I'll also be calling Altrom tomorrow to let them know of this mess so we can avoid this happening to other D21 owners. In the meantime I'm going to see if we have a regular NAPA bearing, if not I'll be going to Nissan.

 

I'm pretty sure this was the source of my crappy mileage. It's already easier to roll the truck in the garage. Amazing how something so little can affect the powertrain that much, but it is in the direct line of power.

[moparvwfreak]

i ahd the same issue with the one in my 620 but then realized i forgot the washer that was under the nut. after that it spun nice and free. no issues.

[JDM510]

my dads d21 got crappy gas economy

 

then we got a 240sx with the same motor and it gets twice the miles its crazy the truck just liked to suck down gas

[HRH]

Well, the drivetrain rolling resistance is good now. Unfortunately I'm still at 15 mpg babying the truck. So something is wrong. I called my Datsun guru tonight, who has the same version of truck, except 2wd, not 4x4. He's getting 35 mpg in his, though he does drive very conservatively on the street. On the race track he's balls fast.

 

Anyway, going to check a plug or two, seeing as the truck runs fine, it might be a coolant temp sensor thinking the motor is too cold and dumping more fuel, going to start with the plug reading. Something's off though. I drove the piss out of my previous hardbody and got 22-24 regularly. 15 is way too low for the motor and gearing.

[datzenmike]

Is it in limp home mode? It defaults to an over rich 'safe' mixture.

[HRH]

The last time I checked the ECU, it was 5 and 5, meaning all clear. Seems to run normally, only has one o2, and it's new. Not sure yet, haven't gone out to the garage. It's cold. :D

[HRH]

Well, I dicked around with it. Plugs were a little black, cylinders looked black on the tops of the pistons like carburetors, so definitely rich. The oil was the most telltale. Smelled gassy. Looked fine, but yeah, probably way too rich.

 

Got a weird code that was suspiciously close to coolant temperature sensor, but wasn't sure which mode I was in at the time and then when I did get to mode 3 for self-diagnosis, it blinked 5 reds 5 greens indicating normal operation.

 

Either way, considering the computer may think everything is normal, think I'll replace the coolant temp. sensor for good measure and because it's cheap and a possible cause that would be undetected by the ecu, and see if that changes anything.