big problems

mildtowild

mildtowild

Custom Upholsterer
I swapped my rear axle to one out of a 2001 blazer which was supposed to be 3.42 but driving it a short distance i quickly realized something was wrong. it turned out to be a 3.73(i I know i should of checked first). so i pulled the front drive shaft to get home as it was 3 in the morning but only got 1 mile before it no longer will move. I believe it should drive ok as rwd so what did i break? i can hear the front output spinning when i try to drive .
 
Foot Performance

Foot Performance

Donating Member
Re: big problems

More than likely I would think it was in the t-case I would think it would be noisy. But could easily be in the trans forward clutch or somthing like that
 
dgoodhue

dgoodhue

BuSTeD 4.3
Re: big problems

It could be the newer rearend is fubar/maybe something with the rear drums. Jack it up, pull the universal joint and try to spin the rear tires.
 
Quickstop [UK]

Quickstop [UK]

Combating adversyty.
Re: big problems

neutral?

ouch...sounds like a headache. Trans case is connected by a chain and the front spins so prob not not the trans case. Then again, I don't know how they split the power...

Trying to figure out if the rear ratio would mean that it was dragging or pushing the whole way in comparison to what the trans case was doing...I'm thinking 3.73 would end up pushing and the trans case with the front was trying to go slower so something was binding up.

What speed were you at and what made you realise something was wrong?

When the trans case spins, what does the rest do? Your driveshaft turn?
 
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blk00z28

blk00z28

Forced to by choice
Re: big problems

Hell I thought when I read it the first time he just swapped the "axel." lol
 
jwaller

jwaller

Evil Genius/SyTy Guru
Re: big problems

I don't know if you have super hearing or what but I can't hear my front propshaft flange turning when the trucks on the lift and I'm standing by it. flatbed it back to the house and pull the xcase. I bet you will find your problem in there.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: big problems

That definitely sounds bad.

2 possibilities jump out at me:

1.) The Viscous Coupling in the transfer case is done and isn't able to send power to the rear wheels. The way these transfer cases work is they MUST have a connection to the front wheels (at about the correct speed) to not completely overwork the VC. You may have had one that was marginal and you killed it, or

2.) You broke something in the driveline. If you can push it with the trans in park, either the VC is done (see above) or something is fragged somewhere in between the axle and the park pawl in the transmission. Some possibilities include a broken tcase input shaft, trans output shaft, etc.

Either way, you're going to need to spend some time diagnosing the problem. And you absolutely MUST put matching gears in (either swap the rear or the fronts to fix it). I'd suspect that the VC is done and needs to be replaced. Not sure that anybody ever came up with an approved method for checking the VC.

'JustDreamin'
 
Don W.

Don W.

Stab it and steer it
Re: big problems

DaveP said:
Not sure who would "approve it", so my 'method' for checking the VC is not "approved". But I've posted it at least a dozen times over the past year or so. And I know for fact that it will identify a smoked, or locked vicious clutch. I've had very good results using my checking method.

You're flat wrong that no one has come up with a checking method. I came up with mine in the '90s, and have been posting about it for over a decade.
Click to expand...

Not sure but I think there is even a "method" mentioned in the manual.

BTW way I have used TC (Syclone). Might be more rebuildable than the one being discussed.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: big problems

DaveP said:
Not sure who would "approve it", so my 'method' for checking the VC is not "approved". But I've posted it at least a dozen times over the past year or so. And I know for fact that it will identify a smoked, or locked vicious clutch. I've had very good results using my checking method.

You're flat wrong that no one has come up with a checking method. I came up with mine in the '90s, and have been posting about it for over a decade.
Click to expand...

Sorry, there was a big discussion of how to check out / evaluate the VC / used tcase a couple years ago, and nothing was mentioned about it. Nobody (at that time that was participating in the discussion) could suggest a (preferrably simple) method to be able to evaluate a used tcase (say at the junkyard). That may be slightly different than the test method you have (I've been on here for several years and haven't seen your method) so maybe its an apples / oranges thing.

So, you got a link to said methodology / discussion? And for that matter, shouldn't a piece of information like that be in a Sticky?

Sorry to be wrong about something. It's only happened twice now.......I wish.

'JustDreamin'
 
midnightbluS10

midnightbluS10

Banned
Re: big problems

Possibly this?

Position the truck with all four wheels off the ground. [Hoist]. Put the trans in neutral. Put a bar through the rear driveshaft yoke and jam it against the frame or body so the rear shaft can't turn. Put another bar on the front driveline, and attempt to turn the front. You should feel a very strong resistance, but you must be able to turn it in relationship to the rear.

If you cannot budge it, it's locked.
Click to expand...

http://www.syty.net/forums/showpost.php?p=650079&postcount=14

search for author davep keyword viscous
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: big problems

midnightbluS10 said:
Possibly this?



http://www.syty.net/forums/showpost.php?p=650079&postcount=14

search for author davep keyword viscous
Click to expand...

Ok, that explains why nobody could come up with a junkyard test method. You need to be able to hold the input and rear output shafts and spin the front, and nobody could come up with a decent way of doing that.

That test method also doesn't account for breakage in the trans. Granted, you should find that when you pull the tcase and check that the output shaft doesn't spin (while in park) and does spin in D or R.

Still think there should be something along the lines of a sticky for a few of these little tidbits.

'JustDreamin'
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: big problems

DaveP said:
I've checked these in the junkyard, with the case on the ground. Find a driveshaft, or take a rear output yoke with you. Stick the shaft in the rear output with a bar through it. Find some bolts (or pins) for the front output and put a bar through them. Leave the input free to turn.


No, but it is intended to check the T-case, not the trans. The trans has to be in neutral for the test. The input must be free to turn.

Like almost anything, if one has a solid understanding of how something works, and is not guessing, or working with 'bad' information, then it's possible to come up with a diagnostic proceedure to figure out if it's OK or not.
Click to expand...

Definitely guilty of working with bad info. I was under the impression that you needed to hold the input shaft as well. Shame on me for not thinking it completely through and relying on others.


Your method of checking in a junkyard would be reasonably simple. I'm a little annoyed that nobody managed to come up with that tidbit when it was discussed earlier (like I said, it was probably 2, maybe 3 years ago).

So, to summarize you really need 3 things to test a junkyard unit: Tcase to be tested, and a front and rear driveshat that fit the tcase (or other bits to engage the front and rear output shafts). Use the rear shaft as the lock (lay it 90 degrees to the tcase), stand on the tcase (unless it's still in the truck), and use the front propshaft as a gigantic breaker bar to spin things over. If things move really easy, VC is done. If it doesn't move at all, VC is done. If it moves some, but not easy, tcase is reasonably OK. Seems reasonably simple.


Thanks for the info. I've got a project that I'm thinking of now that will ultimately require a good 4472. This will help sort the good from the not so good. (oh, and maybe help the OP figure out whats wrong with his truck too).

'JustDreamin'
 
J

jstblz

New member
Re: big problems

Anyone ever see this?

3880991887_a620c6aec3_b.jpg
 
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