Prop Shaft

What exactly is the prop shaft? In an attempt to look intelligent is it the thing that connects the wheels to the gearbox, thus turning them (rear wheels if a rear wheel drive, front wheels if a front wheel drive) or is it something completely different and should I have an embarrassed look on my face...

Reply 1

OMGWTF

If I remeber rightly...its the shaft between the gearbox and differential. On lorries and trucks you can see them spinning around underneath

The differential then supplies power to the two rear wheels

There won't be one on a FWD car

Reply 2

Jonathan

...otherwise known as a driveshaft.

Don't get confused with halfshafts - these are the little shafts from the differential to each wheel.

Reply 3

FlutterByKisses

ok.. so does this mean i have the general jist? (well kind of anyway)

so if it were to snap... its goodbye back wheels? and do they have some weird bolt thing? apparently they do on fords anyway and you need a special tool?

Reply 4

OMGWTF

It would take quite a bit to snap, ALOT of pressure, from the engine, and if its a Fiesta I doubt its the engine that could snap it.

If it snapped now power would get to the back wheels

Bolt? Well, still don't know if you mean prop shaft or half shaft

Anyway, why? Garage trying to rip you off?

Reply 5

FlutterByKisses

its not my car that has a problem... its a ford seirra... asides from knowing its a 2 litre ford sierra and its black i don't know anything about it. lol.

apparently somethings snapped (think its the prop shaft) needs replacing. Could get it done fine apart from something to do with a bolt or nut or something that can't be undone because need a special tool... (tool similar to what are those things called? not a spanner, a socket something? i don't know - apparently similar to tool you use on wheels, but those ones aren't long enough, hence need for a special one? Yes, I've confused me totally now, so bound to have confused everyone else...)

But anyway, the whole point is apparently this car could be fixed for free/cheap if someone had this tool.. but apparently only ford have them and you'd need to call out a ford specialist person purely for use of this tool and then they'd want to replace everything with brand new parts, and charge ridiculous prices per hour... too much money. Oh, I also vaguely recall something called a doughnut being mentioned in the conversation, and how they'd want to replace it with a new one even though theres nothing wrong with the old one...

Basically I need a cheap way to fix the car... but seeing as I don't know what I'm talking about if anyone else does I'll be totally amazed...

Reply 6

OMGWTF

doughnut

A doughnut shaped piece of rubber and metal is used when you connect the shaft to the differntial, they take a LONG time to wear out and probably won't need to be replaced.

If its not long enough, if you had the tools you could probably have a collection of socket extensions to get at it. Or, you could do it the proper way, make the tool yourself :wink:

But im sure you don't have the facilities to do that

Maybe try asking at a Sierra club? Its probably car specific

Reply 7

snmichaels

Driveshaft/Propshaft goes from transmission to the rear differential. I seriously don't think the shaft itself will break, but more likely the u-joints.

If I remember correctly (it's been awhile since I changed them on my mustang), they're like these little cross shaped things that are on each end of the driveshaft. It is what connects the drive shaft to the end of the trans, and connects the driveshaft to the beginning of the rear differential. Looks like this:

Those usually fail and the damage that results will depend on which end of the driveshaft it breaks. If at the rear (where it connects to the rear differential), it will bounce around very violently and smash up the underside of your car, then eventually fall out completely. If it breaks at the front, it could easily rip out the entire rear differential assembly (axles, suspension wheels, halfshafts).

I don't if the Sierra comes with a driveshaft safety loop which goes around the driveshaft which will prevent this sort of thing from happening.

The only problem that might result of a bad driveshaft itself, is horrible vibrations if its bent. This can cause further problems with the trans and possibly the engine.

--------------

Oh, and there shouldn't be any tool that you're not able to get yourself. Changing the u-joints requires only handtools. If your local tool shop doesn't carry it, order it when you get the name of the tool required. Just go on a Sierra website as mentioned above, and ask what tools will be required to do the job. They'll know.

Reply 8

OMGWTF

If it is serious and you need new parts. Theres probably thousands of Sierra's rotting away with decent prop shaft, even if you only need the smaller bits

Reply 9

Jonathan

Nice diagram and explanation snmichaels.

It's worth mentioning that a doughnut can also be a rubber spacer in a driveshaft, that absorbs twisting shocks (excess torque) and prevents too much strain on the metal parts of the drivetrain, especially the differential and shaft itself:

It's just a lump of rubber that connects two halves of the driveshaft; in this case, it's right next to the U-joint (AKA universal joint or CV joint) but could be in the middle of the shaft.

Should be very easy indeed to replace.

Reply 10

davedave

The reason you would have to replace the donut aswell is because the propshaft and 'donut' are balanced as an assembly. Also how cheaply are you able to get the car? They are about for very cheap anyway and it might not be worth fixing.

You may be able to find a complete propshaft with rubber 'donut' for free or quite cheap because sierras are often used as donor vehicles for parts required in building some kit cars. The propshaft isn't usually a part used, so someone might be throwing one away or have one lying around their garage.

What year is the sierra from? The type of gearbox used changed around 1989 I think, so if you find a propshaft make sure it's the right match.

Reply 11

FlutterByKisses

hey guys, thanks for for all the help. At least I know what my boyfriends going on about now (the sierra is his car). I think he's gonna give up on it, especially since someones now given him a new car which only needs to be taxed and MOTed (and apparently it should get through the MOT fine) and I think he's going to some car place on saturday to look at cars too...

Those diagrams posted are great. I am trying to learn about cars, they do interest me, and I do understand things better when they are presented to me in a picture or diagram or something. Thats how I learnt how an engine works... lol. My bf drew me lots of pictures to explain it all...

Anyway, thanks for all the help, and slightly off topic, snmicheals - you have a mustang?! which one? hehe, sorry, but I think they're cool cars.