Builds Cruisermatt's FJ62 Build-up (4 Viewers)

[cruisermatt]

I can almost guarantee whatever the reason is for it it's a positive improvement seeing as how long they used the previous design diff case.

I'm now REALLY wanting to examine a 100-series 9.5" rear diff... I've wanted to put 100 diffs front and rear in mine for awhile for the stronger pinion, I just haven't been able to get solid verification that my existing 30-spline lockers will work in those carriers.

 

[White Stripe]

I think Nitro used 100 series diffs on the 70 series they built. They also used 32 spline axle shafts front and rear. Pretty beefy.

 

[cruisermatt]

I think Nitro used 100 series diffs on the 70 series they built. They also used 32 spline axle shafts front and rear. Pretty beefy.

I don't know if custom shafts to gain an extra 2-splines is really worth it, but if one could reuse their 30-spline side-gears or locker then it would all be of-the-shelf stuff for a stronger pinion.

 

[Cruiserdrew]

I'd like for someone who really knows to discuss oil circulation in the differential. Clearly that happens.

I *think* that with standard rotation (ie rear use), the ring gear flings oil up into the passage in the top of the case. Then gravity carries it down to the outer pinion bearing, from there it flows to the inner pinion bearing and returns to the case.

That's what makes me wonder about reverse rotation-ie front use. My pinion is tipped up enough I close the filler and add an extra quart of gear oil through the breather-hoping to make sure the outer pinion bearing has adequate lube.

If you think about it, there is no way to "splash lube" the outer pinion bearing. It's not in a spot that gets any splash, and is contained inside an iron cylinder.

Anyone really know?

 

[cruisermatt]

Paging @Golgo13

 

[Golgo13]

Thats easy!
There are two oil passages in the diff housing.
Here is an 80 front with masking from painting still.

 

[Cruiserdrew]

80 front doesn't matter. It's the 80 rear in question.

And especially how does the oil circulation work with the differential in reverse location, like running an 80 rear, in a 60 front housing.

 

[Golgo13]

You are overthinking it. Front and rear are basically the same design in different sizes. The ring gear slings the oil up the passage enough to lube the bearings. In both cases the ring slings oil into the upper passage and it drips through the bearings and drains back through the lower passage. No pressure is needed. and it obviously works, or you would be frying bearings all the time.

Where is @NLXTACY with an external pump+cooler option for the pinion bearings?

 

[Cruiserdrew]

You are overthinking it. Front and rear are basically the same design in different sizes. The ring gear slings the oil up the passage enough to lube the bearings. In both cases the ring slings oil into the upper passage and it drips through the bearings and drains back through the lower passage. No pressure is needed. and it obviously works, or you would be frying bearings all the time.

Where is @NLXTACY with an external pump+cooler option for the pinion bearings?

Ok, but we're talking reverse rotation. No slinging of oil up into the upper oil passage. Is there enough push into the lower passage to keep the bearing lubed? I've run reverse rotation "normal" diffs for years without problems, but I'd like to know how it works. Because it doesn't look like it should.

 

[Golgo13]

Should be fine.
That oil really gets moved around

 

[cruisermatt]

Where is @NLXTACY with an external pump+cooler option for the pinion bearings?

Now THAT I like the sound of!

 

[cruisermatt]

You are overthinking it. Front and rear are basically the same design in different sizes.

In 60/62 we run 9.5" front and rear, and both diffs are the same, not mirrored. The front runs in "reverse rotation" on these trucks. If you think about it Toyota probably never intended for any of their 9.5" diffs to be ran in the front for any type of high speed or extended trips, why they put an 8" reverse-cut in the front of the 80. 60's are part time so the front diffs usually never see action on the street. Usually off-road at slow rotational speed.

 

[cruisermatt]

@Cruiserdrew i think the conclusion is that the reverse-rotation really doesn't make a huge difference because the ring gear is slinging oil regardless.

 

[cruisedeisel]

I fixed a drive shaft like that once. It didn't last long. Us a longer rear DS next time and cut it down. Easy!

 

[cruisermatt]

I fixed a drive shaft like that once. It didn't last long. Us a longer rear DS next time and cut it down. Easy!

What aspect didn't last?

 

[cruisedeisel]

I can't even remember, it was in high school when I used to jimmy things all the time.

 

[cruisedeisel]

But the truck did have a 400 v8 and 35 inch tires. Might of had something to do with the failure? Maybe a heavy foot too.

 

[KWalkerM]

I think you will be fine running the shaft. It looks a hell of a lot better than the one that was on my last 60. I crushed mine on a rock and rewelded I think a Ford shaft since it was the same diameter. It was not really close to straight (you could see the uneven rotation easily) however I balanced it with several buckshot pellets from an old shotgun shell and a few duck load BB shells. It actually did really well with no vibration until 55-60mph since the shot self balanced like gold balls in 40 inch tires. It lasted over 2 years to the end of the life of the truck.

 

[cruisermatt]

I welded my front driveshaft myself as well to cut costs. However I do plan on getting a new driveshaft because I do want to be able to run down the freeway in Fwd in case something grenades in the full-floater rear just to get me back home.

I have the same concern however I have a front lock-right so FWD is pretty unsafe on the street for me. If I go on extended offroad trips (+200 miles) I will have a spare rear driveshaft for sure, back when I had an H41 and factory Toyota-length shafts I carried a spare just haven't made a spare for the swap yet. In terms of breaking rear-end parts if I go to GSMTR this year (800 miles from home) I will most likely be bringing a spare third member and a spare front and rear wheel hub with already-packed bearings, and fresh wheel studs and drive studs. In addition to the full set of spare axles I already have.

I think you will be fine running the shaft. It looks a hell of a lot better than the one that was on my last 60. I crushed mine on a rock and rewelded I think a Ford shaft since it was the same diameter. It was not really close to straight (you could see the uneven rotation easily) however I balanced it with several buckshot pellets from an old shotgun shell and a few duck load BB shells. It actually did really well with no vibration until 55-60mph since the shot self balanced like gold balls in 40 inch tires. It lasted over 2 years to the end of the life of the truck.

Yeah, and this is for the front so it will never see speeds like that. Thanks for the input.

 

[KWalkerM]

I have the same concern however I have a front lock-right so FWD is pretty unsafe on the street for me. If I go on extended offroad trips (+200 miles) I will have a spare rear driveshaft for sure, back when I had an H41 and factory Toyota-length shafts I carried a spare just haven't made a spare for the swap yet. In terms of breaking rear-end parts if I go to GSMTR this year (800 miles from home) I will most likely be bringing a spare third member and a spare front and rear wheel hub with already-packed bearings, and fresh wheel studs and drive studs. In addition to the full set of spare axles I already have.



Yeah, and this is for the front so it will never see speeds like that. Thanks for the input.

Mine was too, the speed wobble was never an issue because who drives at 55 in 4wd/FWD anyways? I mean I had taken it up to those speeds but I am stupid/crazy and still thought it was a bad idea.