'95 4x4 Front Diff Problem

I bought my '95 Blazer 4.3L v6 4x4 with 50K miles on it in Dec. 2004. Changed it over to all synthetics, and it has been pretty solid. Had the typical problems...4wd actuator disconnected from vaccuum line and Rt front hum in 2wd that goes away in 4wd. The dealership always said it was probably the "spider gear," whatever that is. Sounds like a part of the front diff.

Here's the urgent problem... The hum has been getting progressively worse. Went to the grocery store tonight & put it in 4HI just to make the hum go away (it's annoying). When I went to turn into a parking space, it was like I'd slammed on the brakes. The front end groaned, and I had to apply significant throttle to get it to move at all.

Backed out and switched into 2HI, and it cleared up. I even tried putting it in reverse and brake-torquing it to adjust the rear brakes. Began turning relatively-tight circles both directions in 2WD. No problems except for the hum. Switched to 4HI, and it was AGAIN like I'd slammed on the brakes.

Brought the truck home and discovered that the front diff-to-driver's side output seal is leaking a bit. Topped off the front diff with gear oil and went for a spin. It was great. Quiet. Took it to a parking lot and turned it both ways in 2HI. No problems.

Then, during a turn, switched into 4HI. BANG!! It sounded like someone hit the transfer case or front diff with a sledge hammer! The front wheels grabbed HARD, again like someone put on the brakes. It left skid marks in the parking lot. Switched back to 2HI for the drive home, and the groaning sound was back.

What's going on?

That's why we are never suposed to drive in 4wd on dry pavement. I won't drive in 4x4 unless I know that there is a good chance that I'll need it.

What you've done by driving in 4wd is caused everything in the drive train to bind, stressing the full system out.
Your basicly lucky that you have 2wd now.

I hope that you only damaged the transfer case, but with the leaking front axle leak I wouldn't hold my breath.

Your transfer case is a chain operated unit, and if you can pull it there's a good chance that you can re-build it yourself. Although I've never tried.

The front differential is another story. It's hard to remove and a mechanic friend of mine won't even go near them, even though he tackles normal differentials all the time.

About the origional hum.
I've never had it in my rig, so I wouldn't be suprised if someone ran it low on oil at 1 time.

I've got a first generation front differential already pulled here that you can have, but you'd have to figure out how to transport it.
If I have to move it it's going straight to the dump.
It has 4.10 gears so you'd probably have to switch the rear gears, and you could run monster tires without running out of power. (Although your motor would rev fast without the tire upgrade while going down the hwy)

Thanks anyway for the offer on the front diff. I can get a salvage unit installed for about $500, and I'd spend that much on new tires by going to a 4.10 unit.

That's the first I've ever heard about not running 4wd on dry pavement...maybe I've been living under a rock! When I got the truck the 4wd was inop due to the vaccuum line being disconnected under the battery tray...so I guess I just check the 4wd from time-to-time. Also, it's the only thing that makes the front end hum go away. Most of the mechanics that I've talked to about this situation seem to think it's the front diff that's the problem. I haven't heard any other speculation about the transfer case.

Assuming that it's just a front diff problem, can I still drive it safely in 2wd, or should it be repaired immediately? Since repair estimates range from $500 to $1900, I could use some time to come up with the cash.

Driving it as it is is always a risk.
However if it's already fried you won't do any additional damage, your just risking a big tow bill.

If you can get a differential from a self serve autowreck and install it yourself you'll probably save $300 - $400.
There's only 1 problem bolt to worry about (Assuming that it's the same as mine)
I believe that they intended this style of wrench with a big of-set to be used in that location, I didn't have 1 accessable.
http://www.wihatools.com/images/Heyco/475BoxPix350.jpg

Good luck

Thanks for the input. I've found a 3.42 gear ratio front diff at a boneyard for $150, so I think I'm gonna go ahead and try it myself. My Chilton's manual gives a decent procedure, and thanks for the tip on the offset box wrench. Is that 18mm?

One more question... The manual says to disconnect the Pitman arm & idler arm from the steering linkage (center link) and pull the linkage forward to get it out of the way. It also says to use a steering linkage puller (J-24319-01) and a steering linkage installer (J-29193/4) for the job instead of a pickle fork. Are these tools necessary? I have a pickle fork, but don't have the puller & installer they spec...

Any other tips before I tear into this job?

Ok...last night I tore into the job. Got the replacement front diff at the boneyard and cleaned it up. Drained the gear oil through a coffee filter to make sure it wasn't full of metal shavings. It looked fine.

But now I'm stuck...literally. The existing front diff just WON'T come out! It's exasperating.

I followed the directions in Chilton's guide to the letter, but I just can't get clearance for the pinion flange (the part that connects to the driveshaft) to roll up and forward far enough for the top mounting ear to clear the frame. It's SOOOO close, but no cigar. It keeps whacking into the exhaust pipe (where it meets the D/S manifold) and the underside of the transmission (I think...could be the engine).

Does anybody have a tip for how to get a little more clearance?

I have two ideas: First, I could remove the collar that connects the exhaust pipe to the D/S manifold. Problem is, I don't think that's going to give me quite enough room. Second idea is to remove the pinion flange...but I'm not sure how to do that. If it's a real pain, I'd rather try the exhaust first.

HELP!

Don't really know...but... would jacking up the engine and pulling the exhaust from the manifold give you enough clearance??? Just a thought, it might work for you.
Good luck, and let us know what works for you.

Don't really know...but... would jacking up the engine and pulling the exhaust from the manifold give you enough clearance??? Just a thought, it might work for you.

I don't know either...if I tried that, what would I have to take loose to get the engine free? Motor mounts, right? Even then...how much clearance could I expect without tearing something up?

It's a thought...any other advice anyone?:banghead:

I know this is an old thread, but if you havent figured it out you have take the front axle out in two peices. Its really easy about six bolts and its in half.
Then you can remove the right side then the left.

. . . put it in 4HI just to make the hum go away (it's annoying). When I went to turn into a parking space, it was like I'd slammed on the brakes. The front end groaned, and I had to apply significant throttle to get it to move at all.


There's a differential in the rear axle so that when you make a turn, the rear tires can turn at different speeds relative to each other. In 2wd, the hubs for the front tires are unlocked and the front tires can spin at different rates relative to each other. There's a second differential in the front axle to allow the front tires to turn at different speeds relative to each other while driving in 4x4. However, there is no differential in the transfer case between the front and rear driveshafts, which means that the front and rear driveshafts turn at the same speed. During a turn, all four tires want to turn at different speeds. But without a differential between the front and rear axles, the four tires cannot spin at independent rates. So, while driving on snow (dirt, mud, loose gravel, etc. - all reduced friction surfaces) in 4x4 the front tires will actually break some traction so that the front tires can either slide on the slippery road or spin in the snow, which you probably barely feel or don't feel at all.

If you use 4x4 on dry pavement, the friction is too great for your truck tires to slip or spin easily, which is why you came to a rapid halt and left skid marks in the parking lot.

WOW!!!! I guess this thread is a little old. I just noticed that now. Just call me 'Ol Eagle Eyes!

By the way, repair manuals do not always tell you every step in the repair process. On my Escort, neither Chilton nor Haynes manuals indicate to remove the crankshaft pulley, an essential step in changing the timing belt.