To VC or not to VC (1 Viewer)

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So you did read it?

But it's not about rotational speed, it's about torque. The Toyota document only talks about torque. ...

How many times does it mention speed difference? If there is no speed difference it's a complected paper weight, the more rotational speed difference = more limited slip action, assuming it's properly working.
 
How many times does it mention speed difference? If there is no speed difference it's a complected paper weight, the more rotational speed difference = more limited slip action, assuming it's properly working.

The VC does not split speed! It splits torque. If you remove your front drive shaft, just because you see the zero-load front shaft spinning doesn't mean there's enough torque being generated to even overcome the static friction of the drive line.

The point is that your 'proof' that the VC doesn't work is invalid. You're not demonstrating what you think you're demonstrating.
 
How much load is on the engine in that situation?

It's a pretty simple concept.

Not that simple, whatever the VC can deliver, depends on it's condition. Have been involved with several rigs with a stripped drive plate, where the owners thought the trans was bad, severely slipping, because they were attempting to drive on the VC.
 
How much load is on the engine in that situation?

It's a pretty simple concept.
Exactly the load that the engine would see if the front tires were on ice, or one tire was in the air. Exactly the situation you might want torque to transfer to the other axle in.

Let me put it another way. You are the only person who can't seem to understand what's going on here. I have never been involved in a conversation on this forum about the VC with someone who can't grasp the concepts discussed here. So, there are two possible reasons for this. Either you are wrong, or everyone else is.
 
The VC does not split speed!

The VC works because of the speed difference between the two shafts, the more difference the more force is applied, attempting to equalize the difference.

It splits torque. If you remove your front drive shaft, just because you see the zero-load front shaft spinning doesn't mean there's enough torque being generated to even overcome the static friction of the drive line.

The point is that your 'proof' that the VC doesn't work is invalid. You're not demonstrating what you think you're demonstrating.

Please explain the difference to the VC between; a tire with no traction, a stripped drive plate or having a drive shaft removed. Hint, there is none.
 
Wow. I give up.

Likely a good idea, the hole you are digging is getting pretty deep, may need lockers?:hillbilly:

The VC is a silicone fluid coupling, works similar to any other, for example a fan clutch. When both shafts turn the same speed it does nothing, when one turns faster, shearing force is generated attempting to make them turn the same speed.
 
@jpoole ( OP), I assume you have made your mind up about purchasing a new VC and seen the price? My advice if your VC is toast then bin it or use it as a conversational door stop and fit CDL button, as you enter an area of 'iffy' traction press the button.........job done!

Regards

Dave
 
@jpoole ( OP), I assume you have made your mind up about purchasing a new VC and seen the price? My advice if your VC is toast then bin it or use it as a conversational door stop and fit CDL button, as you enter an area of 'iffy' traction press the button.........job done!

Regards

Dave

This thread has been effective at helping me think it through a lot more. Current plan is to pull the VC and run without it once I get the front shaft/axle back into the action. Soon after I'll install the CDL switch as time allows. I can't imagine a scenario ahead that would include me installing a new or good used VC at this point. Maybe if my truck was a full resto cream-puff or something, just to keep it all original, but it's far far from that! Seems like just getting the front-end back in order will resolve my occasional wheel spins in the wet, hopefully that's the case.

Lot's of good info here even if a bit of a misunderstanding arose. VCs are in a lot of vehicles so I'd guess that there is some good info on them out in the web should questions remain. From what I understand at this point the 80 series VC is weak in comparison to VCs in other implementations that must lock up more strongly when rotational differences are present.

You folks and the info/discussions on this site are one of the main reasons that 80s are great.
 
what are the symptoms of a locked VC?


When manouvering on dry pavement or any surfaces with good traction, you will feel the transmission binding, you may need a little extra gas to get the car to turn, tyres tends to scrub or squeal, none of this is good for the drivetrain over a prolonged period.

Regards

Dave
 
Lot's of good info here even if a bit of a misunderstanding arose. VCs are in a lot of vehicles so I'd guess that there is some good info on them out in the web should questions remain. From what I understand at this point the 80 series VC is weak in comparison to VCs in other implementations that must lock up more strongly when rotational differences are present.

You folks and the info/discussions on this site are one of the main reasons that 80s are great.

The modern VC is a whole different animal, electronic controls and even the ability to make a 'proper' CDL almost (but not fully) redundant. And with many 4x4 using the brakes to apply braking force to one wheel or more, this may see the end of the VC, CDL and.LSD, take the now quite elderly LR TD5 as an example. The principle of braking one wheel is great but IMO not the best system for careful manouvering off road, it requires a lot of wheel spin to activate the traction control, the result is that progress tends to be a bit of a lurchy affair.

IMO and IME a good solid lock regardless of centre or axle is a good as it gets.

Regards

Dave
 
Most limited slip differentials have a “torque bias” ratio. The ratio of how much load on the slipping side (say 1) to how much load it can transfer (bias) to the side with traction (say 3). That’s what separates them from lockers, they still need some traction on slipping side to work. I assume the VC has similar limitations and thus the front drive shaft removed is not a valid test.

I spent lots of time with the original Jeep Quadratrac (with clutches as a limited slip) and in a pickup with the full time open center diff NP203. I have witnessed 1 wheel drive with the NP203, being stuck on wet ice on a LEVEL parking lot. Never had that problem with Quadratrac, did get clutch chatter on tight parking lot turns.
 
Most limited slip differentials have a “torque bias” ratio. The ratio of how much load on the slipping side (say 1) to how much load it can transfer (bias) to the side with traction (say 3). That’s what separates them from lockers, they still need some traction on slipping side to work. I assume the VC has similar limitations and thus the front drive shaft removed is not a valid test.

I spent lots of time with the original Jeep Quadratrac (with clutches as a limited slip) and in a pickup with the full time open center diff NP203. I have witnessed 1 wheel drive with the NP203, being stuck on wet ice on a LEVEL parking lot. Never had that problem with Quadratrac, did get clutch chatter on tight parking lot turns.

Agree on clutch type, but the VC is a fluid coupling, so operates differently and has differing limitations. There is likely a way to figure the ultimate torque transfer, but they are variable depending on the shaft speed differential. They work just fine with a shaft missing, or stripped drive plate, etc, up to the capacity to transfer torque, that depends on the condition of the VC. If that type of abuse is continued, it will be dead in short order.
 
@jpoole Your internetting is strong! That second video was fun to watch. My takeaway, LSD in all 3 diffs work well on ice. I think that the 470 had ATRAC... seemed to work well too. But, "real" 4wd is needed to climb things. (nothing surprising there) This goes back to my believe that AWD stuff... and our VC is for ice. It won't make a difference in dirt (not truly a low traction surface).

I was curious about this whole topic, so I did a test like in your videos yesterday evening. In my driveway, I put my front two wheels in the ice and back two on dry ground. I got some wheel spin but my rig did pull forward. I turned it around... rear 2 wheels on the ice for the next run. Same result. I didn't take any video and I couldn't really see how much spin there was from the drivers seat. I could see a patch on the ice where the tire spun, though. I wasn't filmed, scientific and I have no idea if it was the VC the moved my rig forward or have juuuust enough coefficient of friction on the ice.

We're having a heat wave in New England right now and it's raining. So, my ice patch will likely be ruined by the evening. If I get an opportunity later this year, I'll try to set up another test and get someone to film it.
 
Pull it and throw it in the scrap bin. I’ve seen them split open and fill the case with a green goo. Or in the case of this 97, filled the case with metal which inturn required sourcing a whole replacement.
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