FWD broken, 4WD = RWD only

[Riff]

Today running some errands a curious thing happened. 2wd quit working in the Tercel, but the car is still mobile in 4wd-- power only going to the rear wheels.

Here's how it happened. Currently mixed conditions on the roads, with packed snow turned ice on less used roads, and bare wet pavement on main streets. Approaching the intersection of my icy side street and the bare main road, I shifted out of 4wd (which was necessary to make any progress on the side street) to 2wd (since it should be plenty on the bare pavement). When my opportunity came to enter traffic I began turning onto the bare pavement from the last of the icy surface and the tires were slipping a little as the car started to move forward. When one front tire arrived at bare pavement, there was a soft pop and then no more power at the front wheels. I pushed it off the street and began investigating. Once upon a time I had an old Subaru that had CV shafts that would eat through splines at the front hubs, and when that happened I discovered I could just put it in 4 and drive home in RWD (you could watch the axles spin in the hubs if you rolled down the window and craned your neck a little ). Get another pair of hubs from the junk yard and be set again for a little while. So I put the Terc in 4wd just to see what would happen, and it did move-- clutch functional, all the gears felt normal, and no horrible noises.

Drove it home 11 miles that way with out any problems, suspicious noises or any other clues. Thought maybe a linkage on the 4wd shifter popped apart or something, since it is now much easier to put into the 2wd detent, but with some investigation in the manual that isn't possible-- its basically just a lever activated clutch for the rear drive shaft (right?). Failure of the connection between the wheel hub and axle seems very unlikely and on inspection doesn't appear to be the case. Visually the halfshafts look normal, both CV axles are relatively recent replacements (approx. 1 year ago) and it would seem that there have been some noise or other indication that they were set to fail. Flywheel through clutch is fine, clearly, and I'd think the transmission is ok too since it seems to work normally.

I looked through the posts here and it appears this has happened to others a time or two but the OPs never followed up when(if?) they solved or even identified the problem. Any ideas? Shouldn't a front diff failure be accompanied by noise/grinding/lockup instead of a gentle pop? Is there a shear pin? Maybe I just go straight to the front diff cover and have a look?

The Subject: "Pino" 1987 4wd, 179K miles, 5spd, barto lift

[Petros]

not likely the 4wd linkage, because if it was you would not have RWD, which is what the linkage engages. sounds like something broke when the spinning front wheel hit the pavement. If you are lucky it is a CV axle, or spline shaft on the end of the axle, easy to replace. IF not an axle you may have damaged either the front diff or the front out put shaft. If there are no bad noises it seems that a damaged diff is unliky (but still possible).

I would pull the cv axles of the tire that hit the pavement, you trouble is likely there. If you see no issues with it, than you will have to pull the trans and separate the front housing that contains the front diff and inspect it. I may have a spare for you, I have some front housings/parts that might be the same, these are not too difficult to replace. If the front output shaft is broken, than the whole trans has to come apart to fix it, this is more complicated and should likely be done by a trans shop, or find another trans.

[Jarf]

I had the same thing happen once on another turtle, in a previous life.
Occurred in the middle of a left turn with oncoming traffic.
Turns out the "rebuilder" decided it was good idea to weld a new end on for the outboard joint.
Haven't been able to trust rebuilt's ever since.
For the record, it all looked good and there were no noises, just the one slight pop and then the holys*** moment.
Take a really close look at the LF axle just to make sure there isn't some nasty business hiding inside.

[Riff]

I've got the car up on blocks in the shed and unfortunately the axles are fine. I guess the remaining options are front diff and output shaft. Can't say I'm very happy, really had fingers crossed for a faulty axle.

[Petros]

You have to remove the axles to get the trans out, so just remove them all the way before you drop the trans. That way you can double verify it is actually the trans and not the CV axle. good luck.

[Riff]

Thanks for the replies Petros, I was headed that direction (getting axles out in prep for future shenanigans) and discovered the splined portion of the axle snapped off inside the differential. I'll have to figure out posting pictures, its just twisted right off at the base of the splines.



So it would have been more accurate to say the CV JOINTS are fine, since clearly the axle is missing a little something.

Curious, can you see through the diff through the axle holes with the axles out? I've tried bubblegum on a stick to get the broken end out (ok a magnet on a stick...) would it be possible to push the end out from the other axle hole?

Also, drained the differential to get any shards out and didn't really see many, there were a few on the end of the axle shaft and I got a few more with my magnet/stick so I think there's got to be some inside there, could I get away with flushing the case with some lighter oil and epoxying a magnet to the drain plug?

[Petros]

wow, looks like you need a new axle for sure. I think the spider gear would prevent you from pushing the end off from the other side. However, if I recall correctly, you can remove the front diff cover and see the axle end in side the center carrier. You should be able to drive it out with the front cover off. It will not just slide out, there is a spring clip on the end of the spline shaft that locks the axle into place, you have to force the spline shaft out with a pry bar to overcome the spring clip, it pops out when enough pressure on it. So you will have to get behind it and drive it out. If you can not get behind it through the diff front cover, you will have to drill a hole in the end of the axle, tap the hole and than screw a bolt into it and pull it out. I am pretty sure I remember being able to see the inside ends of the spline shaft with the front cover off.

Either way, it is lot easier (and cheaper) to get that broken end out than replace the trans. When you have the front cover off it will also give you a chance to clean out any metal particles from the housing that did not drain out with the gear oil. good luck.

BTW, do you know what brand of axles you were driving on? You also might consider waiting until you get off the ice before shift out of 4wd.

[dlb]

that is a brutal, brutal axle failure, riff. you will have to post pics of the removal of the lodged piece. if the CVs are about a year old, i would consider contacting the manufacturer or rebuilder to complain. maybe ask them to buy you a new axle from a different company.

[ARCHINSTL]

While it is no consolation, yours is the first reported instance of this type of failure. It would be good to document your removal procedure with some pix and post it in the Repair Guides Forum.
Go with new - not reman - axles. GSP are not much more than remans. I used GSP and have been happy; others have used EMPI with satisfaction as well.
Also, install new seals.
Tom M.

[Riff]

I think in future I will shift out of 4 after reaching pavement, up until now I thought I was doing myself ( or maybe the tranny) a favor by having it in 2 on dry pavement. I would never have guessed the axle would twist apart like that, but I think that this is a failure due to fatigue developed over multiple instances rather than just a one event total failure. I was not 'rallying' when it failed, the wheel was merely slipping not spinning at redline, and the car was moving less that 5 mph when it failed. Anyway...

Front cover is off, (which can't be done with out removing the stiffener plate, btw) spider gears do block access to the end of the axle shaft. I will poke around in there and see if I can't slide a lever in behind the spider gear and carrier to push out the broken end. The oil pan is so close that it complicates any activity at the front cover area. I think that I'll end up drilling a hole in the broken piece and using a screw extractor on a slide hammer to get it out.

The axles were reman from NAPA, I looked for GSP and EMPI due to postings here, but wasn't able to locate any for the Tercel by either manufacturer when I needed them--it appeared they were NLA. Does anyone else get a little anxious when Rockauto sends those wholesaler parts-closeout emails? It is easier to find parts for my 1963 Dart...

I'll try to get some decent photos of this as it develops and put something in the Repair guides.

[marlinh]

Wow, I have never seen that. There must have been some sort of stress fracture there already. Our cars don't have that much torque to snap an axle like that.

[Riff]

Piece out.



The splines look fine inside the diff, so a little work to clean out any remaining metal bits from drilling and it should be ready to put back together. Rockauto shows EMPI axles available now, so I think I'll just skip all the hassle of dealing with NAPA and go for a new unit, too bad they weren't available in the first place.

[TURTCEL]

Piece out.



The splines look fine inside the diff, so a little work to clean out any remaining metal bits from drilling and it should be ready to put back together. Rockauto shows EMPI axles available now, so I think I'll just skip all the hassle of dealing with NAPA and go for a new unit, too bad they weren't available in the first place.

Wow that is a gnarly looking shaft nugget. Glad you were able to get that out without a trans removal.

I have read in multiple posts that new axles are the only way to go for these cars. When browsing the net for random parts I was surprised to see that even on autoparts store websites they offered new axles. Guess if they offer new then it might be a recommended way to go for replacement. Most other vehicle axles are all remans.

I have not been totally pleased with EMPI parts myself though. I had a VW Westy and a lot of aftermarket parts for VW's are made by EMPI...but all seemed kind of cheap to me. Sometimes though it is all that is available. I would suggest doing a little more digging for that other company that ARCHINSTL mentioned in his earlier post, might be a better product. I believe you mentioned that they were NLA but the internet has many hidden serets to where things can be found.

Keep us posted on the progress and thanks for posting pics with good written descriptions of the job. It will help current and future members a lot that may encounter the same issue.

Peace

[dlb]

Piece out.



The splines look fine inside the diff, so a little work to clean out any remaining metal bits from drilling and it should be ready to put back together. Rockauto shows EMPI axles available now, so I think I'll just skip all the hassle of dealing with NAPA and go for a new unit, too bad they weren't available in the first place.

wowee! nice work on getting it out so quick. great technique. and it's nice that you'll be back on the road soon without any crazy trans replacement work.

[Petros]

ditto on the nice work! NAPA only sells remans, I tried to order new from them and they hand no supplier that had new ones (they could get them next day). rockauto regularly has new axles in stock, so when they do I buy a set so I always have a new set in my personal parts inventory.

Can you post a close up picture of the broken ends? I want to study the failure face of the axle. I should be able to determine if it was a over load failure or a fatigue failure, or even a failure due to manufacturing defect, but I need a close up picture of the failure face (clean off any grease or metal particles so I can get a good look at the metal crystals).