Viscous coupling/clutch

[smokinsiggy]

Well be damned if I didn't get this info too late on my 90 Safari AWD . Had this jerking , shudder , etc. problem happening for some time and assumed it was the poor design on this transfer case . Few weeks back was coming in off highway and be darned if something went for crap in the driveline . Towed on trailer to Da shop and opened up front differential and found the pinion was entirely gone , just a slimey cone shaped piece of metal with no gears left . Shopped around for used last few days and no luck for finding many AWD models period and the local urban wreckers. During my shopping A GM guru with drivelines told me the viscuos clutch gave out causing with mess . Lets make a long story short, buying new was not going to happen when at times you buy a entire van for $600-$1000 bucks , This baby has nearly 1/2 million KM on it and motor is solid due to good maintenance history . Anyway off the long story . Today we removed the front diff. , cv joints and capped the axles and drove it home 35km with no hitch , smoothed out the ride , gas gauge never moved and the wheels are still on it . LOL . My doubt of this modification is apparent and , whats the worst case scenario on any continued driving as my work van . The transfer case can possibly lock up and throw into neutral or blow to hell . lol . This van has been paid for so many times over that I'm keeping it crossed while driving until additional opinions to my "Has been AWD". Down the road one will come my way and will swap and lift or rebuild for back country mountain fishing rig .

[LiftedAWDAstro]

Since you have removed the front drive section, the van WILL roll on hills when parked! Be sure to either use wheel chocks or set the parking brake.

[smokinsiggy]

Since you have removed the front drive section, the van WILL roll on hills when parked! Be sure to either use wheel chocks or set the parking brake.

This info is greatly appreciated but confuses me on why the transmission will be affected with not locking in park .?? Can you elaborate for a dumbass to understand . Thanks for your input .

[Someone]

I am not sure where you are located in canada but there is a 93 safari AWD in toronto @ trader.com for $299.00

here is a link... but it may not work as that website has some linking issues.

http://www.trader.ca/powerpage/details. ... id=6138826

[LiftedAWDAstro]

The reason it will roll is the viscous coupling in the t-case will allow the t-case to differentiate or slip with out the front driveshaft in. Just park level or use the parking brake.

[smokinsiggy]

The reason it will roll is the viscous coupling in the t-case will allow the t-case to differentiate or slip with out the front driveshaft in. Just park level or use the parking brake.

Thanks for the explanation dude . Not meaning to dispute or contradict your valuable information but yesterday after reading your post gave it a try and was parked on several severe slopes the worst being @45 degrees and she stayed locked up . Hmmm? I'm not confident on this discovery and will take the precaution you mention. Thanks again for the support . If it rolls I'll make sure the bottom is far enough away for the bang . LOL

[mdmead]

The reason it will roll is the viscous coupling in the t-case will allow the t-case to differentiate or slip with out the front driveshaft in. Just park level or use the parking brake.

Thanks for the explanation dude . Not meaning to dispute or contradict your valuable information but yesterday after reading your post gave it a try and was parked on several severe slopes the worst being @45 degrees and she stayed locked up . Hmmm? I'm not confident on this discovery and will take the precaution you mention. Thanks again for the support . If it rolls I'll make sure the bottom is far enough away for the bang . LOL

I'm not so sure his van will roll. If the T-case is truly locked up, that means no differential action will take place.

But using the emergency brake is still the best course of action.

[ScottS]

So the diagnosos was that the transfer case caused the diferential failure ? I just had a similar failure so I am intersted in this topic

[lockdoc]

Like said earlier if your coupling is truly locked it probably won't roll. But personal experience has shown it rolls VERY slowly. As in you park it at night and find it 50 or so feet away in the morning. It is not something you will notice just by parking on a hill and watching it.

[rlsllc]

So the diagnosos was that the transfer case caused the diferential failure ? I just had a similar failure so I am intersted in this topic

I believe this is what happened to the '91 that I have now. The case was locked, and the front end was shot (if I remember right, I may have this mixed up) when Mic bought it and swapped in the '96 Blazer front and 2 speed T-case. I know that I've heard before that the front dif is the weak link, and will be the place breakage occurs if the case gets stuck. My question would be: What caused the case to lock in the first place? running two different sized (or brand, they will very in size) tires front and rear is about the only thing I know of that will do it.
Anyone else?

[smokinsiggy]

So the diagnosos was that the transfer case caused the diferential failure ? I just had a similar failure so I am intersted in this topic

I believe this is what happened to the '91 that I have now. The case was locked, and the front end was shot (if I remember right, I may have this mixed up) when Mic bought it and swapped in the '96 Blazer front and 2 speed T-case. I know that I've heard before that the front dif is the weak link, and will be the place breakage occurs if the case gets stuck. My question would be: What caused the case to lock in the first place? running two different sized (or brand, they will very in size) tires front and rear is about the only thing I know of that will do it.
Anyone else?

Not really sure what caused this problem , bought this van for $1000 bucks over a year ago and 80k km later. Had some problems found later , like 2 broken motor mounts and a hole in the oil pan from resting on the front differential. Fixed this and some other problems like gaskets , axle and trans seals the week before the transfer case crapped out . This van did some jerking off while turning a sharp corner on pavement since day one , everyone spoken about this said it was normal , yeah right if you were still running dexron111. Guess the previous owner wasn't aware like myself that dexron111 wasn't to be used in this unit any longer . Amazing the fabulous dealer didn't service this issue some time ago . LOL , anyway a Genuine GM guru in drivelines told me the viscuos clutch locked up . Now that you mention mismatched brand of tires YES "guilty" to say was running 2 Michelins winter radials on rear and 2 Hankook all season on front . The Hankooks were new and others 70% tread left . When this problem did happen one Michelin gave way either just before or during the event . Bead seperated pretty darn good . Perhaps this was the cause . Be damned if I'll know till I'm into the guts of the transfer case .

[rlsllc]

I wouldn't even bother taking it apart. I've seen several given away. They can be had for very little at a salvage yard, or if you want a real cool van, stick a 2 speed case in it like mine and several others around here.

[dragonvan]

I don't think the change to AutoTrack II would have made a difference in your case. Some one help me out here but isn't the viscous clutch in the Borg Warner cases a sealed unit? When it fails or locks up you need to replace the Viscous clutch as an assembly I know. IIRC it was filled with a thick silicone based substance and was similar to those found in the AWD cars, ie. pontiac bonaville. The sealed silicone based ones worked on the principle that as the fluid sheered it heated up, and the hotter it got the more viscous it became. I know the ones in the cars would fail when different size tires were on, it caused a constant sheering of the fluid and it eventually overheats the fluid and it permantly gets too thick. I wouldn't think that your tire situation would have been enough to cause the problem but perhaps if the original diameters were different enough and added quite a bit to the 30% tread depth difference. It is always a good idea to replace all 4 tires at the same time on any 4WD/AWD vehicle, just as recomended to keep pairs on axles in 2WD vehicles.

If anyone has torn apart one of the BW-4472 t-cases let us know if I'm wrong about the viscous clutch. I have only ever replaced the whole t-case and have never had the opportunity to open one up.

[mdmead]

I don't think the change to AutoTrack II would have made a difference in your case. Some one help me out here but isn't the viscous clutch in the Borg Warner cases a sealed unit? When it fails or locks up you need to replace the Viscous clutch as an assembly I know. IIRC it was filled with a thick silicone based substance and was similar to those found in the AWD cars, ie. pontiac bonaville. The sealed silicone based ones worked on the principle that as the fluid sheered it heated up, and the hotter it got the more viscous it became. I know the ones in the cars would fail when different size tires were on, it caused a constant sheering of the fluid and it eventually overheats the fluid and it permantly gets too thick. I wouldn't think that your tire situation would have been enough to cause the problem but perhaps if the original diameters were different enough and added quite a bit to the 30% tread depth difference. It is always a good idea to replace all 4 tires at the same time on any 4WD/AWD vehicle, just as recomended to keep pairs on axles in 2WD vehicles.

If anyone has torn apart one of the BW-4472 t-cases let us know if I'm wrong about the viscous clutch. I have only ever replaced the whole t-case and have never had the opportunity to open one up.

I haven't torn one apart, but based on what I've read in magazines over the years and a really good post on the SyTy message board, I think you have it nailed.

[rlsllc]

I don't think the change to AutoTrack II would have made a difference in your case. Some one help me out here but isn't the viscous clutch in the Borg Warner cases a sealed unit? When it fails or locks up you need to replace the Viscous clutch as an assembly I know. IIRC it was filled with a thick silicone based substance and was similar to those found in the AWD cars, ie. pontiac bonaville. The sealed silicone based ones worked on the principle that as the fluid sheered it heated up, and the hotter it got the more viscous it became. I know the ones in the cars would fail when different size tires were on, it caused a constant sheering of the fluid and it eventually overheats the fluid and it permantly gets too thick. I wouldn't think that your tire situation would have been enough to cause the problem but perhaps if the original diameters were different enough and added quite a bit to the 30% tread depth difference. It is always a good idea to replace all 4 tires at the same time on any 4WD/AWD vehicle, just as recomended to keep pairs on axles in 2WD vehicles.

If anyone has torn apart one of the BW-4472 t-cases let us know if I'm wrong about the viscous clutch. I have only ever replaced the whole t-case and have never had the opportunity to open one up.

I haven't torn one apart, but based on what I've read in magazines over the years and a really good post on the SyTy message board, I think you have it nailed.

I also agree fully.