Help!!! 4WD won't engage!

[StephenA]

OK, so I finally got the truck up on a lift -been checking fluid levels on 5spd tranny & T-case -everyday, the T-case is always a bit over filled, tranny losing oil slightly. I figure it's the seals between both. T-case chain seems tight enough. When shifting the T-case from 2wd to 4wd high & low, sometimes the front wheels engage but mostly they don't. I figure it's gotta be the 92 vacuum engage and have been wanting to upgrade to electric solenoid... Can't find the threads on this.
Does this mean I've got to rebuild the T-case, even if the chain is tight? The local garage said they think the leaking seals can be replaced by dropping the T-case, as the seals simply fit over the spline and don't require splitting the cases open. Is this true? Winter is coming & I gotta have 4wd in the mountains - I've got clients at 12,000 ft on dirt roads... Help!!!! :eek:

[Uncle Wally]

The 4x4 actuator is actually on the front axle. IT should be quite obvious where it is as all the older axles never had this. I have a 94 that had a bad actuator. Mine is electric (i assumed they all were - didn't know any of them were vacuum operated). GM has a new electric actuator to replace the old style one. There is also a wiring harness that goes with it. Replacement of the actuator takes about 5 minutes with a large cresent wrench.

I am assuming the 92 is a lot like the 94 here.

You can tell if the t-case is working by having someone move the truck slowly forward/reverse while you lay on the ground next to and watch to see if the front driveshaft spins. From there the actuator slides a collar over some splines to engage the front axle.

Waldo

[StephenA]

Dear Uncle Wally (and in this case, you are definitely like an uncle...!)- My wife & I did the inpections you suggested & the fwd drive shaft is rotating fine in fwd & reverse, so it's not the T-Case. Whew! -(although I still need to handle the overfill/seals issue, later...).
I checked out the front axle engagement mechanism, and contrary to what the original owner told me, it is indeed electrical & not vacuum, which makes tons of sense to me. When engaging 4WD, I can hear something like the spines you mentioned being passed over - presumably because the solenoid is worn out, or (hopefully not) because the splines have been worn down by partial engagement. The electrical harness goes to two places: one goes to a visible solenoid & the other goes above it into the diff- probably a engagement sensor or something.
So I suspect my 92 is perxactly like your 94...
Do you know the part number for the stock parts involved or for the upgrade? I'd just love to spend 5 minutes with a crescent wrench. Any things to watch for on R&Ring?
Overjoyed,

[Jim P]

Just a little note.

If the actuator in the front differential is engaging, The front driveshaft will turn when the truck moves even if the transfer case is not engaging. If it were me, I would disconnect the wires on the front differential and then put the shifter in 4-wheel and crawl under the truck to see if the front driveshaft will turn. If the transfercase is engaging you will not be able to turn the front driveshaft.

[StephenA]

Hi Jim,
OK, I backed off the ramp, put it in 4WD Low & climbed up the ramp again, feeling like this time the axle was engaged. Sure nuff, when I crawled under to try & spin the fwd shaft by hand, it was locked this time (which it wasn't when it checked it on the lift this morning). SOooo, that tells me that the spine is probably OK and I just need to replace the solenoid, since the wiring tries to engage everytime, although not successfully.
Uncle Wally, Jim, anyone, what are the advantages of the upgrade & is it a direct bolt on?

[Uncle Wally]

Stephen,

You can get the original style actuator from GM still. I am not sure what the part number is off hand. GM has an update (not recall) on front axels that do not engage or engeage improperly. The update consists of a new style actuator (the new one is a solonoid type device - the old was a gas heated by an electric heating element, causing the gas to expand and engage the axle) The new electric version has an additional wiring harness that is needed to make the system work correctly.

If my memory serves me correctly - list for the old style is about 125.00 (no discount price). The new one is about 50.00 more (no discount price). I usually get a discount for my parts and I spent 100.00 for the upgrade. The wiring harness is a pain to put in. The manual says there is a connection between the engine and firewall that needs to be tapped into. I never found it. I just tapped into the wire at the transfer case (I needed to add some wire).

If I had it to do all over again, I would use the original style actuator and leave everything the same. I never had any problems with the the speed that 4 wheel engaged. It just up and quit working one day.

I would expect that you could find the old style actuator for about 75.00.

To test the actuator, remove it from the axle and hook up some wires to it. Connect them to the battery - and the actuator should actuate if it is good. If not I would replace it. My dealer connection stated that it is a 12v load, so it shouldn't be a problem. Maybe add an inline fuse so you don't melt the wires in your hand.

Waldo

[whatnot]

I would never replace one with the old style. Mine was still working when I upgraded to the new style and it was worth it.
On a cold day it takes forever for the old style to engage. The new one is almost instant.

[StephenA]

This is great, guys! Thanks so much for the assistance. Does anybody know how I can get the new & old part numbers for the actuator?

[StephenA]

Gotta love www.gmpartsdirect.com (http://www.gmpartsdirect.com) and their alternate parts finder:
http://www.gmpartsdirect.com/partsvoice/frameset.cfm
you can find almost anything, often with exploded views. I found the following actuators:
1992-6 Actuator: 26013495
1997 Actuator: 26043590
1998-2002 Actuator: 26060073

Which one is the upgraded solenoid version?

[rjschoolcraft]

I agree with the other guys and highly recommend the new "stepper motor" actuator over the old "thermal" actuator. I converted mine and it is much better.

A side note, though. I had a 1986 S-10 Blazer 4X4 with the "shift-on-the-fly" four wheel drive. It used a vacuum actuated front differential. A diaphragm was mounted on the right inner fender (IIRC). A cable connected the diaphragm to the front differential. When vacuum was applied to the diaphragm, it pulled the cable which pulled the shift fork in the front differential into the engaged position. A small valve was mounted on the transfer case that opened when the shifter selected four wheel drive. This valve failed onece...in the winter, in a snow storm. I simply cut the hose and connected a vacuum source directly to the diaphragm. This gave me four wheel drive until I could replace the valve.

When I bought my Suburban, I assumed that it used the same system. I quickly discovered that it did not. I suspect that's why your previous owner thought your truck used vacuum to actuate. Anyway, a lot of miscellaneous information. Sorry.

[ 10-02-2003, 08:24 AM: Message edited by: ronniejoe ]

[StephenA]

Ron: Great info on the origin of the vacuum story from the owner -good to know & I'm sure this is the case.

Waldo, Jim & whatnot: I have opted for the stepper motor, as it gets really cold at 12k feet in the Rockies winter & I could use the split second engagement in the spring which is prone to mud rivers across the road.

Thanks to you guys, I'm sure my dealer connection can steer me to the updated parts (he matches my online parts discount plus shipping).

If anyone found Waldo's reference to an electrical connection between the engine & firewall to tap into, please sing out...

And thanks to everyone for lowering my blood pressure with all this good advice & helping me find the true cause :D

P.S. Now for the seals between the tranny & t-case. Anyone familiar with replacing these? I am slowly seeping oil from the tranny into the T-case. Do I have to split open any cases to fix this, or will the seals fit over the spline between the two?

[StephenA]

Hi guys. Well I got my dealer to order the update & harness for around 100 bucks. It will arrive in a few days.
I took the original actuator out & ran 12v to it (simply by plugging it back in to it's harness & shifting into 4 low) and it actuated, but not very robustly (I could shove it back in a ways by hand). I put a shaft into the hole the actuator left & pushed in to see how much resistance there was to the actuator, & it seems about equal to the force the actuator was able to muster, hopefully explaining the intermittant operation.
Well see- the step motor will definitely deliver more torque, & if the spline is still there, it should be fine. Soon I'll drain the diff & see if there is metal from the spline.
Anybody have any info on magnetic drain plugs?

[Uncle Wally]

Stephen,

If a 92 is the same a 90 (I know they aren't - but my experience with t-cases is with my 90), there should be an adapter that connects the trans case and the trans. I just looked in my 94 GM Manual and it looks to be about the same type of setup. There should be about 6 bolts that bolt it to each case (trans and t-case). If my memory serves me correctly, the trans crossmember still attaches to the trans tailhousing, leaving the t-case hanging off the back. Remove both driveshafts, the t-case shift linkage, a couple of electrical connections and the six bolts (I don't think it matters which six because you'll need to pull the entire adapter) and the t-case should fall on the floor. I would use a hyd jack to prevent that though! I don't recall which side the seal is installed from, but it easiest when the adapter is the only part your dealing with. Seals should only be a couple of bucks, so that and a couple hours and some new fluid for the t-case (it makes it lighter to lift with no fluid in it) and it should be good as new. Just be carefull with the jack. I smashed the heck out of my hand when I did my 90. Hard enough for me to bang my head on the frame in the process.

Waldo

[StephenA]

Perfect, Waldo -I think your discription corresponds with what I've been looking at under the truck & the picture I downloaded from partsvoice.com; Can't wait to have the Helms manuals for all this stuff!
I'll check it out tomorrow afternoon or Sat. Good news that the seals go in that easy. I'll get some from the dealer and have a go. My floor jack has a table attachment, so hopefully it will go smoothly. I picked up an empty rebuilt NP241 yesterday & figured it at less than 50lbs. But it wasn't hanging over my face either. Creepers can be claustrophobic...
Many Thanks, Wally!

[lupey6.5]

don't waset your time or money on the "updated" stepp motor that gm offers order a posi-lok brand cable acctuator i know jcwhitney offers them but every 4x4 mag has vendors that carry it. about $200 for kit but you will not have to rely on electricity to do anything. i have the updated one on my 94 and sometimes it won't work if the connections are wet! what good is that? i'm gonna replace mine with a posi-lok soon. also enables you to use low range in 2wd, you control fron dif with cable! :rolleyes:

[rjschoolcraft]

Frankly, I wouldn't waste my time or money on the mechanical cable. My updated actuator has never missed a beat in more than five years of service...and I use the four wheel drive several times a week. Maybe we should all go back to pedaling...or maybe horses and buggies. :D

[curmudge1]

There was a thread earlier on the NP241 -- within the past couple of weeks, iirc. There was a link or info about an upgrade to the spring clips that you might want to check out, as long as you'll be R&Ring the t-case. About a $20 upgrade, iirc. I know this is a little vague, but I have a bad case of CRS.
If you page back through the 6.5 forum & look for NP241 in the topic, you should find this thread.

Maybe someone else recalls better? Or has an opinion / experience with that product?

[Uncle Wally]

Stephen,

Picking the t-case up isn't all that tough. Even on your back. It's getting it aligned once you have it up. There is almost no way to balance it so the front drive portion is sitting at the correct angle. You have to make a bracket that goes to one bolt to get it to sit right. Wish I woulda had a table when I did mine. That and a bracket of some sort woulda made it a lot easier.

Good luck,
Waldo

[StephenA]

Hey Wally! Positoning is a bear, yes? This is vital info, -I'm so glad you chimed in... So I can make this bracket myself, yes?

[Uncle Wally]

Stephen,

I would think you could drill a hole in some flat stock and figure out where to bend it so it sits right before you drop the t-case out. It would make it a bit easier. the front to rear angle is not a big deal, it's the fact that it rotates the same as the drive shaft. You'll see when ya get the last bolt out!

Good luck,
Waldo

[StephenA]

Thnaks Wally I'll keep you posted.

[GMCfourX4]

I just did the seal on mine this summer. The T-case isn't heavy, but it was a bit of a bear to get in and out smoothly. The seal between the NV4500 and the NP241 is in a metal plate? between the two, bolted to the T-case. The top bolt on the t-case is a bit of a trick to get to, but the rest aren't bad. Just make sure you do the top on first, and install it after the other bolts are started, b/c at least that way there won't be any extra resistance on the bolt from the weight of the T-case. Once you get the T-case out, its like 4 bolts to remove the plate the seal rests in, then you just tap in the new seal (funny lookin' thing, b/c it has sealing surfaces on both sides) Shouldn't be too tough, and having something like a tranny jack, or some way to grab the thing at the correct angle....

-Chris

[StephenA]

Thanks, Chris- that really helps. Did you replace your seal because it was leaking tarnny oil into the t-Case or the other way around?

[GMCfourX4]

I was actually dropping the t-case/tranny to replace the pilot bearing and input shaft seal on the tranny. When I drained the t-case, I noticed there was WAAAAAY too much fluid coming out, and it was NOT the nice, clean, $6/qt Mobil 1 ATF I had put in there :D The tranny was pushing fluid out from both ends. I THINK I've got all of my seal issues straightened out at this point, though.

Good Luck, it really isn't that bad of a job.

-Chris

[StephenA]

Thanks, Chris. Say- you don't happen to have the part number on that seal (between tranny & T-case), do you?

[GMCfourX4]

Not sure, and I just tried to look it up, and didn't have any luck. I think your best bet is just to call a local dealership, that's where I got mine.

-Chris