Back wheels locked while driving! Please help!

[AlleyNiki]

 

Hello everyone, I'm in deep trouble, and would appreciate any knowledge!

Here's a step by step rundown of 'what happened today': (Mr car is a 1989 aircooled 126)

1. I was driving at about 30km/hr in second gear when I heard a 'bump' come from the bottom rear of the car. A half second later my driving wheels locked, and both wheels skidded for a few metres.

2. The engine was still running because I had pressed the clutch to avoid stalling. But the engine was labouring as if the clutch was still half engaged. I just couldn't get it out of second gear to begin with.  I switched off the engine.

3. Checked underneath the car, no branches or obstacles stuck under there and nothing stuck in engine. Swore a lot.

4. Managed to disengage second gear into neutral and pushed the car into my shed. The car made a weird clunking noise at regular intervals as I pushed it along.

5. I  started the engine again, and whilst in neutral I noticed the engine is a bit out of balance.  It also makes a bit of a weird noise like something is shaking around and whirring. But when I pushed the clutch in this would stop and it would run properly.

6. I put it into reverse and let the clutch out, the car reversed for a metre or so and then the wheels locked and the car bumped to a stop.

PLEASE does anyone know what is happening here? It's either the clutch, differential or gear box but I have no idea which. The gears still seem to be engaging. To my knowledge there have been no oil leaks from the transmission but to be honest I have never filled it up in the two years I've had the car.

The transmission had been making a deal of noise recently, but I thought it was the rubber mounts that had just worn..

Please if you guys have experienced this situation or you think you could help out then please give me a few ideas! Thanks also for all the help in the past.

Alley.

[Rusty's Uncle]

Sounds very much like the gearbox has let go. I was diving my Bis one morning , car was less than 3 years old. Gearbox was fine one minute then 2nd gear just went like it was not there. It went down hill big time after that. My son got through a number of gearboxes on an air-cooled. When I got round to stripping down 4 or 5 gearboxes I found different problems in each box. Apart from the usual 1st/reverse wear problem there were worn bearings, chipped gears & broken selector forks.

[damon500]

Sounds like it has possibly broken some teeth on the differential- have seen this happen before on Nikis and it can cause a lock up like you describe.
You could try draining the gearbox oil- i'm fairly sure you will find some evidence of what has broken!
Sorry to hear your news..

[AlleyNiki]

 
Rusty & Damon, thanks for responding so quickly.

I'm thinking either case (diff / gearbox) are well worth investigating.

Also, i had a look under the car after getting it on ramps. I checked out the rear axles, where they enter the diff and found :

1. That just after the rubber boot on each axle there is about 2mm of shiny metal showing.

and

2. That each axle can be pushed / pulled in and out about a half centimetre.


Is this normal? Can it indicate a fouled up diff?


There is no evidence of oil leaking from the transmission. It's all clean - ish.


Thanks in advance

[Rusty's Uncle]

The driveshafts have to have an amount of end to end free movement to allow for the independent rear suspension movement.

[Darrell]

I'd take the box out. You might be able to save it.

[lilgreencar]

That happened to me! Driving along and then the rear wheels lock and you skid...

I tore into my transmission and found a little shop of horrors of broken mechanical parts. See here for my full sad story:

http://fiat500club.org.uk/clubchat/viewtopic.php?f=1&t=5735&p=18225#p18225

Hope yours is salvageable. I wasn't able to find the various brackets and damaged bits as separately available parts and ended up getting a whole replacement transmission...

-lilgreencar

[AlleyNiki]

That happened to me! Driving along and then the rear wheels lock and you skid...

I tore into my transmission and found a little shop of horrors of broken mechanical parts. See here for my full sad story:

http://fiat500club.org.uk/clubchat/viewtopic.php?f=1&t=5735&p=18225#p18225

Hope yours is salvageable. I wasn't able to find the various brackets and damaged bits as separately available parts and ended up getting a whole replacement transmission...

-lilgreencar

 

Dear God!! Maybe that's what that noise was...

How difficult is it to take out the gearbox and open it up? Fortunately I have new transmission bearings - I bought them along with a new 1st/rev shaft.

Will drain the oil tonight and see what I get coming out..

[gsxr126]

That happened to me as well. When I opened up the box it turned out to be the 1st gear shaft. I also bought a replacement 1st/Rev kit and tried to assemble it with just that kit. The main shaft was also worn but i thought i could get away with it. Turns out just replacing with the kit didnt fix the prob and i ended up buying a completely new gearbox in parts (dont do it that way - very expensive for Oz niki owners, you're better off buying one complete if thats the way you're headed).

In regard to removing the box from the engine, I would remove engine and box, and rear panel, bumber etc as one piece, then separate the box from the engine (i found that trying to remove the box from the engine whislt still in the car was near on impossible due to the two studs that the gearbox slips over)

You might want to try getting a new mainshaft as well. That should fix your prob, but it also introduces another - the mainshaft and diff gears need to be matched so you will need a new/matched ring gear.
Sorry to be bearer of bad news. It doesnt end there either. With my new box, I need to have it filled with at least two litres of oil to stop the bearings going dry, which means it leaks like crazy from the axle seals, but keeps the scary bearing noises away.

[AlleyNiki]

In regard to removing the box from the engine, I would remove engine and box, and rear panel, bumber etc as one piece, then separate the box from the engine (i found that trying to remove the box from the engine whislt still in the car was near on impossible due to the two studs that the gearbox slips over)

You might want to try getting a new mainshaft as well. That should fix your prob, but it also introduces another - the mainshaft and diff gears need to be matched so you will need a new/matched ring gear.
Sorry to be bearer of bad news. It doesnt end there either. With my new box, I need to have it filled with at least two litres of oil to stop the bearings going dry, which means it leaks like crazy from the axle seals, but keeps the scary bearing noises away.

I was thinking of pulling the engine out seperately and fitting a new clutch as I bought one recently.. This is possible isn't it, and then taking out the gearbox afterwards?

With regards to replacing the ring gear, do you mean the main wheel in the differential?

[gsxr126]

No, the main is spun by the ring gear in the diff, Its the smaller one of the two.

[AlleyNiki]

Well guys, I pulled out the transmission and opened the gearbox up.

Nothing - no damage...! (Diff is fine as well)

Gears- fine, no teeth missing
Bearings - OK, bit of a noise coming from one but I have a replacement
Shifter forks - Fine.

However I have noted one thing: the input gear shaft on top (with the three gears on it) seems to be sliding forwards. If I push from the clutch end, it slides along, because the frontmost  bearing slides out halfway! (Like a cm)

Is this normal???

I don't have to push hard either. And when this happens, the gears on that shaft mesh with others on the output shaft (below) and jam up.

Also, the lower output shaft seemed to be sticking after engaging a gear - and it would get to a point where I couldn't turn it from the input shaft. By total accident I decided to take apart the synchro hub just behind the worm drive that works the speedo, and those three synchro tabs fell out.

Maybe the locking spring had shifted or something when it all jammed up. I replaced the tabs with the locking spring around them and put it all back..

And now the gears are working fine..... Hmmm

Anyone have any ideas why the top gear shaft might be sliding? There does not appear to be any way to lock its bearing (the one closest to the front of the car) in place. I don't want this to happen again..

Cheers!

Alastair

[Darrell]

Nothing on the subject in the online manual on this site?

[GTMaster]

Regarding the moving bearing, all the bearings are not allowed to move about in the housing (either rotate or slide out). They're put in with a tight fit and have to be tapped in (better if they're properly pressed in) when replacing. Interesting, maybe the housing has worn out. If that's the case, you can try to glue the bearing back in, make a bush/sleeve for it or replace the housing...

[AlleyNiki]

Maybe use locktite or whatever it's called?

I've got a new set of bearings for the gears though, I'll just fit those (got them when I purchased the repair kit)

There's an online manual??? Now I'm learning.

Thanks

Alastair