Does driving without propshaft destroy t-case/VC
- Thread starter jeepruby04
- Start date
Couger1968
Dazed and Confused
Re: Does driving without propshaft destroy t-case/VC
I agree with you,that is kind of what I was trying to say.That is why you need a output drive shaft to not cause issues. I was just wondering if under extreme circumstances you could push past a weak or failing vc and roll in park. If the vc was bad it looks like you would not know it under normal driving.
I agree with you,that is kind of what I was trying to say.That is why you need a output drive shaft to not cause issues. I was just wondering if under extreme circumstances you could push past a weak or failing vc and roll in park. If the vc was bad it looks like you would not know it under normal driving.
Last edited:
Re: Does driving without propshaft destroy t-case/VC
Here is what Mattw said that started the ball rolling.
Here’s what I said…….
Here’s the response from Dave that started all this discussion/debate/arguing……
We’re arguing over nothing.
I said the fluid won’t shear, you said the VC would transmit the torque. We’re BOTH right. The VC transmits the torque, without (or with very minimum) shearing of the fluid. You have said it yourself. The VC is the link between the sun and ring gears. With the front propshaft removed it must hold the torque between the sun and ring. With the propshaft in, this link is the pavement.
The confusion is coming in our wording. You have been screaming “The VC must carry the load”, I have been screaming “The VC won’t shear the fluid”. Both are correct.
What we should be asking is “How much torque does it take to shear the fluid?”, and then answer that by speculating/calculating the amount of torque it takes to drive the truck, and how often the fluid will shear to the point of locking the coupler (due to “humping”). Does simply driving to the store create enough of a force differential to shear the fluid, and create a problem? What about a full pull on a dyno or at the dragstrip? At what point is the VC no longer capable of transmitting the required forces between the sun and ring to keep them stationary, and begin to spin the front shaft significantly more than the rear?
I still contend this is a communication problem, not an understanding problem. I told the guys in chat last night this and I’ll stand by it. Give me a beer, a couple napkins, a pen, and 20 minutes, and I guarantee we would be on the same page.
It’s been a good discussion Dave, and I look forward to the next time we meet so we can hash this out in person with a pen and paper, and real words. I’ll buy dinner if you buy the beer, and we’ll meet in the middle on this!
Here is what Mattw said that started the ball rolling.
”mattw” said:
Here’s what I said…….
”me” said:
Here’s the response from Dave that started all this discussion/debate/arguing……
”DaveP – Post #9” said:
We’re arguing over nothing.
I said the fluid won’t shear, you said the VC would transmit the torque. We’re BOTH right. The VC transmits the torque, without (or with very minimum) shearing of the fluid. You have said it yourself. The VC is the link between the sun and ring gears. With the front propshaft removed it must hold the torque between the sun and ring. With the propshaft in, this link is the pavement.
The confusion is coming in our wording. You have been screaming “The VC must carry the load”, I have been screaming “The VC won’t shear the fluid”. Both are correct.
What we should be asking is “How much torque does it take to shear the fluid?”, and then answer that by speculating/calculating the amount of torque it takes to drive the truck, and how often the fluid will shear to the point of locking the coupler (due to “humping”). Does simply driving to the store create enough of a force differential to shear the fluid, and create a problem? What about a full pull on a dyno or at the dragstrip? At what point is the VC no longer capable of transmitting the required forces between the sun and ring to keep them stationary, and begin to spin the front shaft significantly more than the rear?
I still contend this is a communication problem, not an understanding problem. I told the guys in chat last night this and I’ll stand by it. Give me a beer, a couple napkins, a pen, and 20 minutes, and I guarantee we would be on the same page.
It’s been a good discussion Dave, and I look forward to the next time we meet so we can hash this out in person with a pen and paper, and real words. I’ll buy dinner if you buy the beer, and we’ll meet in the middle on this!
Couger1968
Dazed and Confused
Re: Does driving without propshaft destroy t-case/VC
I think you would in a sense turn it into a overdrive.
I think you would in a sense turn it into a overdrive.
toolmann
Member
Re: Does driving without propshaft destroy t-case/VC
interesting reading...
i dont have the knowledge ya'll have of the inter-workingd of the t-case, but do have some real world data on funtions. 3-4 years ago my front diff failed(grinding/banging).. i pulled the front shaft & drove it for a season like that(8kish). multiple trips consisting of hundreds of miles.. never had a problem with the truck moving when in park, or not moving in drive.
i replaced the front diff with a 4x4 unlocking unit & control it with a cable. been 3 seasons of about a 50/50 split of driving it with the front diff locked & unlocked with no adverse effect or weird drivability issues. i did notice of how 'heavy' the steering wheel is when the diff is locked. also on the highway it picked up 4-5 mpg(from 13-14 to 16-18, depending on my lead foot, consistant speed, ect..)
overall, the cable set up works well. the front diff is ok when engaged & it acts like it did when the stock diff was in there, minimal tire spin at WOT.
when unlocked, smokey white burn outs! ..little better fuel economy
i love it!
again, its been probably around 25k miles since i did the conversion.. its a summer truck. it rarely goes to the tradk. iv dropped the t-case fluid to check for buring or metal.. soo far, soo good.
not to say all trucks will respond the way mine has.. my diff had 160k on it when it croked.. still the stock 180K t-case(i have a back up just in case) & my motor is built pretty good.. cam/ported vortecs/4 bolt/50s/ect., but not tuned to its full potential.. i keep wanting to tune it, but...
fwiw..
interesting reading...
i dont have the knowledge ya'll have of the inter-workingd of the t-case, but do have some real world data on funtions. 3-4 years ago my front diff failed(grinding/banging).. i pulled the front shaft & drove it for a season like that(8kish). multiple trips consisting of hundreds of miles.. never had a problem with the truck moving when in park, or not moving in drive.
i replaced the front diff with a 4x4 unlocking unit & control it with a cable. been 3 seasons of about a 50/50 split of driving it with the front diff locked & unlocked with no adverse effect or weird drivability issues. i did notice of how 'heavy' the steering wheel is when the diff is locked. also on the highway it picked up 4-5 mpg(from 13-14 to 16-18, depending on my lead foot, consistant speed, ect..)
overall, the cable set up works well. the front diff is ok when engaged & it acts like it did when the stock diff was in there, minimal tire spin at WOT.
when unlocked, smokey white burn outs! ..little better fuel economy
i love it!
again, its been probably around 25k miles since i did the conversion.. its a summer truck. it rarely goes to the tradk. iv dropped the t-case fluid to check for buring or metal.. soo far, soo good.
not to say all trucks will respond the way mine has.. my diff had 160k on it when it croked.. still the stock 180K t-case(i have a back up just in case) & my motor is built pretty good.. cam/ported vortecs/4 bolt/50s/ect., but not tuned to its full potential.. i keep wanting to tune it, but...
fwiw..
Re: Does driving without propshaft destroy t-case/VC
I like how you picked apart a post in the beginning of the thread when my recollection was still fuzzy. My apologies for overstepping those understandings early on. You have corrected some misconceptions I had about what was inside, and I think I've helped you along the way understand some of the physics. We have obviously moved past that. And you are correct, sort of, again, I don't think we agree. I think we're saying different things that are both true.
This however still sticks to me
You still have a misunderstanding of the physics involved when the front propshaft is disconnected. My wording above is vague. I should be more specific. There is NO significant torque differential between the front and rear wheels to create the necessary slip in the VC. There is a differential force available from the input to the rear output. With no propshaft, there is no resistive force on that shaft.
To answer the original posters question.....is it safe to run with the propshaft out for a dyno run, or a run to the store for some milk? I'm going to give the same answer I did in the "Is it safe to run mistmatched tire sizes? thread. It's as "safe" as the owner is comfortable with. Is it harder on the VC? Yes. Is it going to instantly grenade your transfer case? No. How much it hurts it, and how fast it will fail is something that cannot be analyzed here. How much risk you are willing to assume as an owner is up to you. There is plenty of anecdotal evidence to support running without it for short periods of time without instant death to the viscous coupler.
At any rate it has been a good discussion, and I think we've both learned something here. Hopefully some others have as well.
I like how you picked apart a post in the beginning of the thread when my recollection was still fuzzy. My apologies for overstepping those understandings early on. You have corrected some misconceptions I had about what was inside, and I think I've helped you along the way understand some of the physics. We have obviously moved past that. And you are correct, sort of, again, I don't think we agree. I think we're saying different things that are both true.
This however still sticks to me
DaveP said:
You still have a misunderstanding of the physics involved when the front propshaft is disconnected. My wording above is vague. I should be more specific. There is NO significant torque differential between the front and rear wheels to create the necessary slip in the VC. There is a differential force available from the input to the rear output. With no propshaft, there is no resistive force on that shaft.
To answer the original posters question.....is it safe to run with the propshaft out for a dyno run, or a run to the store for some milk? I'm going to give the same answer I did in the "Is it safe to run mistmatched tire sizes? thread. It's as "safe" as the owner is comfortable with. Is it harder on the VC? Yes. Is it going to instantly grenade your transfer case? No. How much it hurts it, and how fast it will fail is something that cannot be analyzed here. How much risk you are willing to assume as an owner is up to you. There is plenty of anecdotal evidence to support running without it for short periods of time without instant death to the viscous coupler.
At any rate it has been a good discussion, and I think we've both learned something here. Hopefully some others have as well.
BMFB
Not to scale
Re: Does driving without propshaft destroy t-case/VC
so...there is this drum thing. its got what looks like the sun gear for the planitaries. Also included is a big ass cog for the mating chain. also included on said drum is a grease filled mother****er of a vicous clutch. ALSO on this drum is a very thin gear that lines the outside of said grease filled clutch.
it appears as though the input shaft goes through the center of all of that drum, including the sun gear, and locks into a ...sprag...on the inside of the case...on the otherside of the planetary gear set. I am guessing that said sprag...being driven by the input shaft...is connected to the planet gear retainer.
This planet gear retainer gets spun by the engine, and tryes to spin the sun gear, and the outer ring gear, through the planitaries. keeping in mind sun gear is attached to huge drum.
The big ass clutch and sun gear meshes in...and that thin gear that goes around the outside of the clutch meshes into the outer ring...which is how the clutch connects to both the inner gear and outer gear.
so if you were to remove the front shaft, the clutch would have to keep the ring gear and planets spinning together...otherwise all of the force could transfer into the sun gear and it would spin...probably 30% faster than trans output speed. The clutch having to work like that would generate alot of extra heat...bad for clutch
so...there is this drum thing. its got what looks like the sun gear for the planitaries. Also included is a big ass cog for the mating chain. also included on said drum is a grease filled mother****er of a vicous clutch. ALSO on this drum is a very thin gear that lines the outside of said grease filled clutch.
it appears as though the input shaft goes through the center of all of that drum, including the sun gear, and locks into a ...sprag...on the inside of the case...on the otherside of the planetary gear set. I am guessing that said sprag...being driven by the input shaft...is connected to the planet gear retainer.
This planet gear retainer gets spun by the engine, and tryes to spin the sun gear, and the outer ring gear, through the planitaries. keeping in mind sun gear is attached to huge drum.
The big ass clutch and sun gear meshes in...and that thin gear that goes around the outside of the clutch meshes into the outer ring...which is how the clutch connects to both the inner gear and outer gear.
so if you were to remove the front shaft, the clutch would have to keep the ring gear and planets spinning together...otherwise all of the force could transfer into the sun gear and it would spin...probably 30% faster than trans output speed. The clutch having to work like that would generate alot of extra heat...bad for clutch
jeepruby04
New member
Re: Does driving without propshaft destroy t-case/VC
Sooooooooo, after reading this thread multiple times and studying the pictures and watching the video, I was just as lost as when I asked the question.:squint: However, I had a break through last evening and I believe the key to this is in the planetary gear set.
If you don't understand how a VC works try this http://auto.howstuffworks.com/differential5.htm For our application the outer plates are attached to the drum and the gear teeth replace the shaft the picture shows attached at one end. Also imagine the inner shaft as hollow (input shaft goes through it) with the sun gear on one side and the chain sprocket on the other end.
After looking at DaveP's drawing I realized I didn't know how planetary gears worked, so I went here http://science.howstuffworks.com/transport/engines-equipment/gear7.htm This shows what happens when you hold any one of the components.
Ring gear held: This would be like removing the propshaft. The ground is "holding" the the rear wheels as you try to drive the truck. The planet carrier is driven by the engine causing the sun gear to spin. This would result in no movement of the vehicle. Now add the VC into the equation, the drum of the VC is attached to the ring gear so it will not move. The sun is attached to a hollow shaft that goes through the VC and has the chain sprocket on the other end. The only thing connecting the sun shaft and drum is the viscous fluid. The only way to move the vehicle is to transfer the spinning energy of the sun shaft through the fluid so it expands and causes the plates inside the VC to grab.
Sun gear held: This would be like removing the rear driveshaft. The ground is "holding" the front wheels. The planet carrier is driven by the engine causing the ring gear to spin. Once again the vehicle doesn't move. Add the VC again. Now the drum is spinning around the sun shaft and has to transfer the spinning energy through the fluid until the plates grab.
Planet carrier held: This is like the truck parked on an incline with the propshaft removed. The engine is "holding" the planet carrier. The rear wheels are rolling forward causing the ring to rotate in one direction and the planets turn the sun in the opposite direction. Imagine the drum of the VC moving clockwise and the sun shaft anticlockwise. There wont be enough shear of the fluid to cause the plates to grab so the only thing that will stop it is a fellow SyTyer putting a block of wood in front of your tire.:tup:
Now to sum up. As you can see the VC does have to work for any of the above conditions. It will sustain damage over a period of time. As DaveP said, when and how long it will take will vary. This is indeed up to the individual to decide if the risk is worth it, for me it's not.
Sooooooooo, after reading this thread multiple times and studying the pictures and watching the video, I was just as lost as when I asked the question.:squint: However, I had a break through last evening and I believe the key to this is in the planetary gear set.
If you don't understand how a VC works try this http://auto.howstuffworks.com/differential5.htm For our application the outer plates are attached to the drum and the gear teeth replace the shaft the picture shows attached at one end. Also imagine the inner shaft as hollow (input shaft goes through it) with the sun gear on one side and the chain sprocket on the other end.
After looking at DaveP's drawing I realized I didn't know how planetary gears worked, so I went here http://science.howstuffworks.com/transport/engines-equipment/gear7.htm This shows what happens when you hold any one of the components.
Ring gear held: This would be like removing the propshaft. The ground is "holding" the the rear wheels as you try to drive the truck. The planet carrier is driven by the engine causing the sun gear to spin. This would result in no movement of the vehicle. Now add the VC into the equation, the drum of the VC is attached to the ring gear so it will not move. The sun is attached to a hollow shaft that goes through the VC and has the chain sprocket on the other end. The only thing connecting the sun shaft and drum is the viscous fluid. The only way to move the vehicle is to transfer the spinning energy of the sun shaft through the fluid so it expands and causes the plates inside the VC to grab.
Sun gear held: This would be like removing the rear driveshaft. The ground is "holding" the front wheels. The planet carrier is driven by the engine causing the ring gear to spin. Once again the vehicle doesn't move. Add the VC again. Now the drum is spinning around the sun shaft and has to transfer the spinning energy through the fluid until the plates grab.
Planet carrier held: This is like the truck parked on an incline with the propshaft removed. The engine is "holding" the planet carrier. The rear wheels are rolling forward causing the ring to rotate in one direction and the planets turn the sun in the opposite direction. Imagine the drum of the VC moving clockwise and the sun shaft anticlockwise. There wont be enough shear of the fluid to cause the plates to grab so the only thing that will stop it is a fellow SyTyer putting a block of wood in front of your tire.:tup:
Now to sum up. As you can see the VC does have to work for any of the above conditions. It will sustain damage over a period of time. As DaveP said, when and how long it will take will vary. This is indeed up to the individual to decide if the risk is worth it, for me it's not.
RealFastV6
@jb_and_his_coffee
Re: Does driving without propshaft destroy t-case/VC
...since Dave didn't explicitly say it I'll belabor the point; there's about a 99% chance your front diff failed in the first place BECAUSE your VC is locked.
...since Dave didn't explicitly say it I'll belabor the point; there's about a 99% chance your front diff failed in the first place BECAUSE your VC is locked.
Horsehammerr
New member
Re: Does driving without propshaft destroy t-case/VC
Does this mean that you could run a 4x4 front diff. unlocked, as in 2w hi, and not damage the VC in your AWD Transfer case ? I also had this wild thought, can a 4x4 Transfer case be converted to AWD? What I mean is, can a AWD Viscous Clutch be fitted to a 4x4 transfer case ? I wonder about this , thinking it would be handy to retain the 4lo option.
Does this mean that you could run a 4x4 front diff. unlocked, as in 2w hi, and not damage the VC in your AWD Transfer case ? I also had this wild thought, can a 4x4 Transfer case be converted to AWD? What I mean is, can a AWD Viscous Clutch be fitted to a 4x4 transfer case ? I wonder about this , thinking it would be handy to retain the 4lo option.
Last edited:
atomicmecha
I hate rust
Re: Does driving without propshaft destroy t-case/VC
So after reading all of this... twice now to make sure I understand it... I have one stupid question and one decent question...
First the stupid one. I think its stupid because I feel like it has been answered, I just missed it or I'm still slightly confused. But my question is, the input shaft (#19 on our Supplement manuals, page 336 or 7D-10), doesn't it connect directly to the output shaft assembly (#24) and go straight out the back? So in a sense it will always be rear wheel drive or am I missing a step? Just a little loss on that part even after watching the video and looking at all of the pictures. I feel like a good explanation of that area or cracking one of these things open myself will give me that final "Ah-HA!" moment.
2nd question... how does one replace/repair the VC? After reading all of this and some other threads, I feel like the VC on my tcase has locked up and thats is what ultimately cause the front half shafts to snap at the joints. Ever since I brought the truck it would do that hop when making sharp corners that I am familiar with from when I owned a jeep. Same hop will happen when I had the jeep in 4-hi and on dry pavement. So educated guess was that my tcase had locked up at 50/50. This thread confirms that. So... how does one go about fixing a stuck VC? Is there a replacement part? Take it apart and clean it? Is there a thread around here on how to fix it?
EDIT::Nevermind... i found my old bookmark to http://www.drivetrain.com/parts_catalog/transfer_case_replacements_and_parts/bw4472__bw1372.html and see the part I'd need... but if anyone knows a cheaper way...
So after reading all of this... twice now to make sure I understand it... I have one stupid question and one decent question...
First the stupid one. I think its stupid because I feel like it has been answered, I just missed it or I'm still slightly confused. But my question is, the input shaft (#19 on our Supplement manuals, page 336 or 7D-10), doesn't it connect directly to the output shaft assembly (#24) and go straight out the back? So in a sense it will always be rear wheel drive or am I missing a step? Just a little loss on that part even after watching the video and looking at all of the pictures. I feel like a good explanation of that area or cracking one of these things open myself will give me that final "Ah-HA!" moment.
2nd question... how does one replace/repair the VC? After reading all of this and some other threads, I feel like the VC on my tcase has locked up and thats is what ultimately cause the front half shafts to snap at the joints. Ever since I brought the truck it would do that hop when making sharp corners that I am familiar with from when I owned a jeep. Same hop will happen when I had the jeep in 4-hi and on dry pavement. So educated guess was that my tcase had locked up at 50/50. This thread confirms that. So... how does one go about fixing a stuck VC? Is there a replacement part? Take it apart and clean it? Is there a thread around here on how to fix it?
EDIT::Nevermind... i found my old bookmark to http://www.drivetrain.com/parts_catalog/transfer_case_replacements_and_parts/bw4472__bw1372.html and see the part I'd need... but if anyone knows a cheaper way...
![Quickstop [UK]](/data/avatars/m/5/5165.jpg?1570199786){kind=avatar}
Quickstop [UK]
Combating adversyty.
Re: Does driving without propshaft destroy t-case/VC
To answer the first question... Nope!
To answer the first question... Nope!
atomicmecha
I hate rust
Re: Does driving without propshaft destroy t-case/VC
So what's the fix when your t-case is stuck in 50/50 mode? Ie, my typhoon hops around when making tight turns. Puts undo stress on the props haft causing it to almost snap a universal joint. Etc.
Would taking it apart and cleaning it fix it? New seals and such would go with that, of course. I'm just hoping it's not that vc part. Re - reading this makes me think it's still good or else the truck wouldn't move at all. It's other parts of the t-case that's causing everything to stick.
So what's the fix when your t-case is stuck in 50/50 mode? Ie, my typhoon hops around when making tight turns. Puts undo stress on the props haft causing it to almost snap a universal joint. Etc.
Would taking it apart and cleaning it fix it? New seals and such would go with that, of course. I'm just hoping it's not that vc part. Re - reading this makes me think it's still good or else the truck wouldn't move at all. It's other parts of the t-case that's causing everything to stick.
Quickstop [UK]
Combating adversyty.
Re: Does driving without propshaft destroy t-case/VC
50/50 "mode" where the truck is hopping and skipping means your VC plates are seized and the VC has failed. So you need the new VC unit.
50/50 "mode" where the truck is hopping and skipping means your VC plates are seized and the VC has failed. So you need the new VC unit.