Non-functionall 4x4 - Broken CV or diff?

[Tiktiki]

Yay! First thread on the forums!

Sucks that's it's to find a problem.

I tried to go a little hill the other day and my 97 SR5 struggled to even get started on the first bump.
I had rear wheel spin, so I just wrote it off as open rear diff = crap.

Yesterday I decided to finally bleed the front brakes properly.
With only 1 wheel off the ground and transfer case in 2HI, I could spin the axle that is off the ground, but the center shaft would not move at all!!!

From what I understand, either of the CV is broken of the differential itself is shot/gone.

When I spin the driver-side wheel, I can hear some faint gear meshing coming from the diff.

Passenger side is silent (at least the bearing is good!).
There does not seem to be an apparent breakage...

I am about to remove both CVs, as regardless if it's the CVs or diff, they need to be removed to fix it.

CVs are nonexistent at any salvage yard around here, diff are common however (Quebec, Canada).

That, plus frame rot make me want to sell what's left/good and shop for a new 4R...

Anyone had a similar issue? Was it the CVs? How rare is it to have a diff break that way and not cause a rattle/noise when driving (either 2Hi or 4Hi)??

 

[rkntoy]

Which axle did you have off the ground? If it was the passenger one and you were in 2WD your ADD would not be engaged so your front driveline should not be spinning.

Usually when your CV axles break they break the cage that hold the ball bearings which is next to the spindle. Grab the axle shaft in the middle - if the CV is broken you should get lots of movement out of that end.

 

[phattyduck]

Need more info here.

The CV disconnect on the front is right next to the differential. Neither front axle will spin freely of the hub/wheel it is attached to. The front driveshaft (from the transfer case to the diff) should be free to spin by hand in 2WD.

Assuming you have a non-Limited model... Do you get the 4WD indicator light on the dash when you shift to 4WD? (you can do this on dry pavement if you don't take any sharp corners)

-Charlie

 

[RonJR]

Behavior is totally normal. Don't pull out the CV's or diff to fix anything, because nothing is wrong (at least your tests haven't demonstrated anything is wrong.)

Your vehicle has ADD (Automatic Differential Disconnect). When you're in 2wd, the passenger side CV is disconnected from the differential. That frees up the differential gears inside the diff to spin freely, and no torque is transmitted from either CV axle to the front drive shaft. Both wheels turn freely, and the center drive shaft remains stationary.

When you spin the passenger side wheel, you should hear nothing from the diff, since the CV is disconnected from the diff. When you spin the driver's side wheel, you'll hear the spider gears in the diff turn, but that's all.

A better test would be to put it in 4wd with the engine running (so you have vacuum). Make sure the green 4wd light comes on. Then shut off the engine and jack up the front wheels. The center front drive shaft should be immovable, and spinning one front wheel should cause the other front wheel to spin in the opposite direction.

 

[Tiktiki]

Behavior is totally normal. Don't pull out the CV's or diff to fix anything, because nothing is wrong (at least your tests haven't demonstrated anything is wrong.)

Your vehicle has ADD (Automatic Differential Disconnect). When you're in 2wd, the passenger side CV is disconnected from the differential. That frees up the differential gears inside the diff to spin freely, and no torque is transmitted from either CV axle to the front drive shaft. Both wheels turn freely, and the center drive shaft remains stationary.

When you spin the passenger side wheel, you should hear nothing from the diff, since the CV is disconnected from the diff. When you spin the driver's side wheel, you'll hear the spider gears in the diff turn, but that's all.

A better test would be to put it in 4wd with the engine running (so you have vacuum). Make sure the green 4wd light comes on. Then shut off the engine and jack up the front wheels. The center front drive shaft should be immovable, and spinning one front wheel should cause the other front wheel to spin in the opposite direction.

Will test that, I was wondering how I could check this without taking everything apart.

SR5 = Not Limited.

From what I understand, as soon as I put the truck in any 4WD mode, the transfer case is locked. Not like the Limited that runs AWD and locks with the press of a button.

 

[RonJR]

From what I understand, as soon as I put the truck in any 4WD mode, the transfer case is locked. Not like the Limited that runs AWD and locks with the press of a button.

This is correct. There is no center differential inside the tcase, so in 4wd the front and rear drive shafts are locked together.

 

[Tiktiki]

Got the truck in 4WD and 4WD Lo.

Jacked-up the front-end while staying in 4WD modes.
Also started the engine just in case.

In all the situations above, each wheel spins individually.
The front center shaft was locked in both cases, but free in 2WD mode.

I have also checked for any wobble or play in the CVs and they both feel well centered and supported...

I also drove over my phone in 2WD, 4Hi and 4Lo, and in 2WD the center front shaft does not spin. It DOES spin in either of the 4WD modes.

I have a rather large gravel patch as a drive way. Put the truck in 4Hi and punched the gaz to make the wheels spin. I only got 1 rear wheel to spin.
Redid the test a few times in different spots, and always only managed to spin one of the rear wheel (both spun out at some point). Never lost traction on either of the front wheels, which confirms to me that there is no power at the front in 4WD modes.

As for lights/indicators, I only ever have a A/T PARK light if the truck is in park while the T case is in neutral. Nothing else, ever.

Also, if I follow the instructions (the paper still is in the visor!), having the truck in neutral while trying to shift the T Case to 4Lo ends-up in grinding gears sound... Same thing if in neutral and trying to shift out of 4Lo.

The only way I can get to shift it to 4Lo without that noise is by stoping while in drive, setting the truck to park, then pushing the T case shift to 4Lo and releasing the brake. It pops in place nicely without any noise.

If the ADD works with a vacuum line, I think I might have to lift it and crawl under to find a leak...
Where does the diff vacuum connects to on the engine side?

 

[RonJR]

Sounds like your ADD is not working. On the 3rd gen's, it looks like the system is operated electrically. Attached are a couple of files from the FSM which may help you trouble shoot it. No need to open it up and inspect the mechanical stuff right away - the problem is much more likely electrical, either the 2wd-4wd switch on the tcase, or the wiring to the actuator on the diff.

I'm more of an expert on the 2nd gen ADD, so this is about as far as I can get you.

The grinding in neutral may be just because the output shaft of the transmission turns when in neutral, due to fluid coupling. Probably nothing to worry about right now. Get the ADD working first.

 

[Tiktiki]

Sounds like your ADD is not working. On the 3rd gen's, it looks like the system is operated electrically. Attached are a couple of files from the FSM which may help you trouble shoot it. No need to open it up and inspect the mechanical stuff right away - the problem is much more likely electrical, either the 2wd-4wd switch on the tcase, or the wiring to the actuator on the diff.

I'm more of an expert on the 2nd gen ADD, so this is about as far as I can get you.

The grinding in neutral may be just because the output shaft of the transmission turns when in neutral, due to fluid coupling. Probably nothing to worry about right now. Get the ADD working first.

Thank you, that first doc is really useful!

I can hear the relay click when I move from 2Hi to 4Hi and back.

I will unplug the actuator at the diff and put 12v on it to see if it moves. If it does, that just means there is a relay or wire faulty. I had some electrical work to be done anyways (not related, I want a 12V 4ga power lead from the battery to the rear/driver cargo).

 

[Tiktiki]

Well, that was interesting!

97 SR5 is VACUUM-activated.

There is a 2-pin connector at the ADD (I assume for the indicator).
So, I traced the cable from the Pass-side relay to the engine bay where there is two small solenoids to control vacuum. A red and a blue.

When the tcase is in 2WD, the red is active and I had a good vacuum at the outlet (to the ADD). When in 4WD, the red was off and blue was active, again with good vacuum at the outlet (ADD).

I could not reach the ADD-side of the hose but inspected it all the way down and under and there does not seem to be any cracking. In fact it looks like this hose is in the best condition of all of them.

There is a small rigid section right under the driver's floor that looks rusted, but again, access was too hard for tonight.

I think at that point I might just have to drop the diff to be able to remove the ADD and test it... The outside of the vacuum piston looks rotten, it might be leaking right there at the joint/weld.

At that point I might just go to a junkyard and get the ADD and wire harnest off an electric-activated one and retro-fit it. I have all the wires figured out already so it's just a matter of splicing 4 wires...

Thanks all for the help, at least I didn't remove a bunch of parts I didn't need.

 

[Tiktiki]

Found this working diagram for those with a vacuum ADD.

The vacuum one is all grey, while the electric one has a black motor on the back-side (similar to a door glass or wiper motor).

 

[phattyduck]

Well, that was interesting!

97 SR5 is VACUUM-activated.

There is a 2-pin connector at the ADD (I assume for the indicator).
So, I traced the cable from the Pass-side relay to the engine bay where there is two small solenoids to control vacuum. A red and a blue.

When the tcase is in 2WD, the red is active and I had a good vacuum at the outlet (to the ADD). When in 4WD, the red was off and blue was active, again with good vacuum at the outlet (ADD).

I could not reach the ADD-side of the hose but inspected it all the way down and under and there does not seem to be any cracking. In fact it looks like this hose is in the best condition of all of them.

There is a small rigid section right under the driver's floor that looks rusted, but again, access was too hard for tonight.

I think at that point I might just have to drop the diff to be able to remove the ADD and test it... The outside of the vacuum piston looks rotten, it might be leaking right there at the joint/weld.

At that point I might just go to a junkyard and get the ADD and wire harnest off an electric-activated one and retro-fit it. I have all the wires figured out already so it's just a matter of splicing 4 wires...

Thanks all for the help, at least I didn't remove a bunch of parts I didn't need.

'96-'00 4Runners are vacuum actuated. '01/'02 is electric. The vacuum system is plenty reliable (probably more so than the electric), so you don't have a reason to try to change it.

You are well on your way to solving this.
- Your transfer case is working fine
- Your 4WD indicator switch on the transfer case is working fine (that triggers the ADD relay in the passenger footwell, which you are hearing)
- Your transfer neutral indicator switch is working
- Your 4LO indicator switch doesn't really matter (only changes shift points in the ECU during 4LO operation)
- The ADD vacuum actuators are switching vacuum

Your problem is probably in the ADD actuator. It may have just gotten stuck from dis-use, or one of the vacuum lines to it is disconnected right there at the actuator. Once you get under there and check it out, you'll find your problem. You maybe be able to replace the actuator with the diff still in the truck...

-Charlie

PS. You can shift between 4HI and 4LO without grinding in neutral while stopped if you move the lever quickly/strongly between the two position, not stopping in transfer case neutral. Move the lever over to the right, then just move it up in one assertive motion. Coming out of 4LO is the same, just pull straight back, then let the lever go.

 

[Tiktiki]

I am about to go crawl under again.

There is a short-ish section of steel tube bolted on top of the diff casing.

The ADD tubes connect to it, then an other section of the goes to the valves.

I want to disconnect the tubes at the ADD-side and check for vacuum there. If there is plenty, then it confirms it's the ADD actuator that does not work.

There is a 96 at a local junkyard, I might go check if the actuator is still there, and maintenance/rebuild it before trying to remove the one from the truck.

Thing is that the steering rack is in the way to get to the actuator, I am not sure I will be able to remove just the ADD without dropping the diff or the rack...

Anyone know if I can unbolt/lower the steering rack without disconnecting anything?

 

[Tiktiki]

Well, that was quick!

I have no vacuum at the end of the metal section going over the diff casing for the 4WD position. 2WD sucks properly.

I want to try to swap the metal tubes around to see but the other end is a pain to get at (driver-side CV is in the way).

For now I think I will get a piece of tube and swap them around at the actuator to try to make it move, at least I would know if it's good or not.

That metal tube section can be bypassed after (replace with a piece of flexible from the valve all the way to the actuator) if that's the only problem.

 

[phattyduck]

Nice. I was just under the truck yesterday and was going to report that you CAN get the actuator off with the diff in the truck if necessary.

You may be able to blow out the hard line with compressed air... or it may have been crushed by a previous owner/mechanic.

As long as it doesn't get damaged in spinning components, replacing the hard line with continuous soft vacuum line should work fine.

-Charlie

 

[Tiktiki]

Nice. I was just under the truck yesterday and was going to report that you CAN get the actuator off with the diff in the truck if necessary.

You may be able to blow out the hard line with compressed air... or it may have been crushed by a previous owner/mechanic.

As long as it doesn't get damaged in spinning components, replacing the hard line with continuous soft vacuum line should work fine.

-Charlie

Yeah... it's not crushed, but 100% sure it's not clogged either.

You guys think the rust belt is bad... should see up here in Québec what it's like.

It's defenitely just rusted and there is a leak in the metal section, specifically at the driver-side bracket that mounts the hard tubes to the diff casing.

I can hear the hissing of the leak when trying to put it in 4WD.

Didn't had the chance to go to the junkyard yesterday, but if the diff/tube is not there (or rotten) I will just yank a bunch of vacuum tubes around the engine and use that instead.

 

[RonJR]

I will just yank a bunch of vacuum tubes around the engine and use that instead.

Careful, that could cause you more heartache - those various vacuum hoses are there for a reason, and the ECU is likely to get upset if you pull them off randomly. Plus the engine will likely not run as well.

Much easier IMO to buy 6 feet of new hose at the auto parts store for $5.00 and replace the whole run from the vacuum valve down to the diff. I agree with phattyduck, as long as you keep the rubber line away from moving parts and/or exhaust heat, it should be fine.

 

[Tiktiki]

Careful, that could cause you more heartache - those various vacuum hoses are there for a reason, and the ECU is likely to get upset if you pull them off randomly. Plus the engine will likely not run as well.

Much easier IMO to buy 6 feet of new hose at the auto parts store for $5.00 and replace the whole run from the vacuum valve down to the diff. I agree with phattyduck, as long as you keep the rubber line away from moving parts and/or exhaust heat, it should be fine.

I meant pull hoses from the junkyard engine...

Specifically the hoses from the valve down to the metal tube should give me enough to replace the hard tube section. I plan on tiewrap to the old tubes anyways to keep the soft line in place.

 

[RonJR]

I meant pull hoses from the junkyard engine...

Specifically the hoses from the valve down to the metal tube should give me enough to replace the hard tube section. I plan on tiewrap to the old tubes anyways to keep the soft line in place.

Ah, that makes more sense!

 

[Tiktiki]

Annnd it works!

I went and grabbed the two lines from the valve to the metal tubes of the 96'

Then used a piece of brake line as a male-male coupler (it works perfectly by the way). Then ran the now longer hose to the actuator directly (removing the 4" pieces of tube in the process.

The new flexible lines fit in the old metal tubes, it holds it in place perfectly!

What a difference! The truck now moves properly!

Gotta go wheelin a bit to celebrate!