Axle code confusion and questions about a rear differential

[RCWD21]

I recently bought an 87 pathy that needs some pretty extensive work done too it but its nothing I can't handle with some time and patience.

 

So after a few days and a ton of searching with no solid answers I figured I'd ask.

 

Here's my questions:

 

1. The engine bay placard on my 87 says my axle is HG46. And if I understand correctly from the list of code explanations it "should be" an h233b rear end and an r200a front end. On my 90 I have HG43 as my axle designation and it has for sure the H233b and r200a combo.

 

Here's where my confusion begins. I jacked up the rear end of the 87 and it acts like an open differential.. But according to that list it should be an LSD rear end.

 

So what gives? Is that list wrong? I haven't crawled under there yet to look at the rear end and I don't see an orange sticker (my 90 doesn't have a sticker either) so I wasn't expecting much.

 

Also how can I tell the difference between an r180a and an r200a and what does the HG stand for in the axle codes?

 

Question number 2:

 

With the rear end of the 87 in the air and me turning one wheel and the other wheel turning the opposite direction the drive shaft (with the auto transmission in neutral) will spin about 1/4 turn one way and then it will turn about a 1/2 turn the opposite direction and then it will sort of twitch back and forth and then start all over again. Would a severely worn out 233b act like an open diff and cause that sort of behaviour? Sorry for the multiple drawn out questions but I haven't been able to find an answer that clearly states what I'm looking for..

[hawairish]

The axle code doesn't indicate absence or presence of an LSD.

If the tires spin in the opposite direction, that's indicative enough of an open diff.

The difference between an R180 and R200 is very subtle. I think the casings are actually the same, but the internals are slightly smaller on the R180.

I don't know what the HG means.

 

Your observation of the driveshaft is normal. The differential allows the tires and driveshaft to rotate at different speeds...and in the scenario you're in, different directions. When you've got both tires spinning in opposite directions, you've overcome the friction of the spider gears and are transferring almost all the torque directly across the axles, essentially ignoring the rest of the differential. But there's just enough friction to allow the driveshaft to move a little. Assuming you're repeatedly spinning one tire, each time you grab that tire, you might be slowing it down just enough for the opposite tire to be rotating faster than it, which is what creates the reversing effect on the driveshaft. However, with the tires rotating in the opposite direction, you could actually grab the driveshaft and spin it in either direction, or hold it stationary.

 

This scenario isn't a problem because it doesn't occur when driving (and if it does, you've got bigger problems).

 

[JamesRich]

My 87 had an open differential too.

James

[RCWD21]

I was just curious as this differential doesn't behave the same as the one in my hardbody. I hated that damn rear end lol.

 

The vent tube has been broken off and is just hanging behind the pumpkin. I'm planning on swapping in an h233b and an r200a so I don't have to worry about any damage already done to the current rear end and also I love having an LSD in my 90. Even thought about getting a locker for upfront. I've read a front LSD chews through cv axles lol.

[hawairish]

The differential will proportion the torque as needed when you're testing like that. Any differences you're seeing between trucks are due to varying amounts of friction on different components (spider gears, side bearing preload, pinion preload, wheel bearing preload, brake drum friction, etc). If you put both in Park/gear so that the driveshaft remains stationary, you'll see that both differentials behave the same as open diffs. Unless something is broken, of course.

 

Why would you suspect any damage? If you do the above test, the spider gears are fine. If you just lift one wheel, put the truck in neutral, and spin the one tire, you'll be able to test the ring and pinion. This just proves that things are meshing ok, but not that everything is to spec, though.

 

But you're swapping in axles you already have?

 

 

[RCWD21]

The 233b in my 90 acts like it's locked with the wheels in the air. It's got the correct fluid in there.

 

And Im not suspecting any damage, just the unknown factor. I this rig has clearly been neglected and the vent ends are packed with dirt and mud. I'm one that likes to make sure everything is 100% and as strong as it can be before I go and make my way through the woods and wherever else I'm interested in going.

 

The difference swap will be in the future after I get it running and make sure there's not hidden problems with the transmission or other components.

[hawairish]

The 233b in my 90 acts like it's locked with the wheels in the air.

 

What do you mean?

 

I feel like we're talking about both vehicles interchangeably...weren't you talking about your 87? Are you transferring parts around or something?

[RCWD21]

No, you said that either rear end would/should act the same when doing the spin test. My 90 just happens to have a LSD rear end. But eventually the 87 will have an LSD rear end with the correct front differential too. I'm currently getting it back in running condition.

 

So for clarification the 87 has an open differential and I will at some point in the future be swapping in an h233b differential along with an r200a from a donor from the junkyard.

 

My 90 already has thever h233b and r200a differentials and is my DD and will only become a donor if it gets wrecked or damaged badly.

 

This swap won't be anytime soon as I need to save up the money for parts and fluids.

[RedPath88]

HG4x designates the R&P ratio

​HG43 = 4.375

HG46 = 4.625

 

The original axles installed front and rear correspond to the stock engine.

VG30 = Front: R200A / Rear: H233B

Z24 = Front: R180A / Rear: C200

LSD is only designated (to my knowledge) by an Orange sticker on the back of the housing. Look for that, and clean and scrape to be sure, Don't recall anyone ever positively verifying that the sticker has ever fallen off. Just know that even if a housing does not have the sticker, it is still possible that someone swapped in a LSD and matching carrier.

Edited December 24, 2015 by RedPath88

[hawairish]

Your original post didn't say your 90 had an LSD, nor that you had compared the two. When you did mention an LSD, it was in the context of your 87:

 

Here's where my confusion begins. I jacked up the rear end of the 87 and it acts like an open differential.. But according to that list it should be an LSD rear end.

 

But now that we're clear on what has what, the diffs will not act the same. The open diff's tires will spin in opposite direction, and the LSD's tires will spin same direction. Do both tests with the transmission in gear/park and both tires up.

 

Since you have a V6 87, you already have an H233B/R200 per RedPath88. So you just want the LSD?

[RCWD21]

Sorry about the confusion, I didn't word it as best I could.

 

Your original post didn't say your 90 had an LSD, nor that you had compared the two. When you did mention an LSD, it was in the context of your 87:

 

 

But now that we're clear on what has what, the diffs will not act the same. The open diff's tires will spin in opposite direction, and the LSD's tires will spin same direction. Do both tests with the transmission in gear/park and both tires up.

 

Since you have a V6 87, you already have an H233B/R200 per RedPath88. So you just want the LSD?

And red, according to the info you provided I should already have the h233b installed from the factory in the 87 correct? If so why is there an open diff under there instead? What would a severely worn LSD differential behave like? I would assume like an open one right? I'm not familiar with differentials at all. But I guess I'll have to do some homework and take a scrub brush to the carrier housing.

 

Oh and as for the orange stickers coming off, on my 90 it's long gone lol

 

Also could you take a look at my other thread about this 87 in question? There's a few questions I need answered and I can't find any info pertaining to what I'm looking for.

[Slartibartfast]

Ah, I see where you're confused. Open and LSD are both called H233B, even though the guts are a little different. Same gears, same housing. Even the 33-spline rear end in the R50s (versus the 31-spline in WD21s) is still called an H233B.

The concept of the clutch-type LSDs in these is fairly simple. Imagine you've got a standard open diff. As soon as one wheel loses traction, the spider gears send all the power that way, and it peels out instead of pushing forwards. Unhelpful, right? Now stuff a bunch of clutches between those spider gears and the diff casing. The clutches make the spider gears harder to turn, and since spiders only turn when one wheel is going faster than the other, those clutches make it harder to do a one-wheel peel. The FSM says it should take at least 260 lb/ft to make the clutches slip. It's low enough that you don't chirp the tires on dry pavement (like you would with welded spiders or a spool), but high enough to give you a fighting chance off-road.

The clutches can wear down over time, but I can't imagine the kind of abuse it would take to get that 260+ lb/ft down to zero. Much more likely you're rolling on an open diff.

As for the vent tube, unless the rear end is making horrible noises, I would just check the fluid and replace the tube... especially since you're planning to swap in an LSD axle anyway.

[RCWD21]

You just made everything so much clearer! in all my searching I never found that this. Thanks! time to look at yard prices and see if it's cheaper to get the whole rear end or just the internals. Might even look into a locker of some sort lol

 

You learn something new everyday and that's why I love this place. I would have never found that out on my own lol

[Slartibartfast]

No worries! Check out the PD section of the service manual, it's got exploded diagrams for everything.

 

If you want a locker, hold onto the open rear, IIRC most of the aftermarket lockers need the case from the open diff to mount in.

[RCWD21]

Thanks for the tips now I have more questions but they're not related to the rear end. Mind if I pm you slartibartfast? I can't find a picture of a stock vg30i engine bay or of the front of the engine to see what I'm missing and what certain brackets should look like, plus I'm u sure if I can use vg30e brackets or not....

[Slartibartfast]

Go for it, but I'm probably not the guy to ask about TBI--the closest I've come to working on one was scavenging a few bits off a Hardbody. This has all the bits of the TBI labelled, with pictures. Then of course there's the almighty service manual.

[RCWD21]

Well the component lay out doesn't exactly pertain to my questions but I still have it book marked and I completely forgot about nicoclub lol haven't been on there since I had my 240! That was 3 years ago now.