Lack Of Power To One Wheel

[richyb66]

The thing I don't get is that with the prop unbolted from the diff and the box in neutral, I had to use a big screwdriver and a fair bit of effort to turn the prop. This isn't normal.

[richardm6994]

The thing I don't get is that with the prop unbolted from the diff and the box in neutral, I had to use a big screwdriver and a fair bit of effort to turn the prop. This isn't normal.

 

you're right........do you remember how 'floppy' the prop felt on the UJ's?

 

The prop should rotate freely when disconnected from diff and gearbox in neutral........

Edited May 8, 2015 by steamer

[Grim]

failed gearbox bearing?

[Guest 2b cruising]

failed gearbox bearing?

Yup. That's what I was thinking earlier. If it stalled in third on the rollers, it will happen again with wheels off the groun.

If it still occurs without the prop,you can totally disregard any diff problems.

This is the first check I would carry out.

[richyb66]

Can someone confirm if the S7 uses a one piece prop with a uj at each end and a sliding spline into the box?

 

Having done bits and bobs on Stu's car, it's obvious that removing the diff to inspect the prop is pointless. I don't think the prop will move easily on the front splines and the issue seems to be at the front end.

 

If it was me, I'd break out the biscuits, pull out the engine on it's own and then withdraw the box and prop as one piece.This way you can pop the top cover off the box and rotate the input shaft while seeing what's happening inside.

[speedtripledan]

Can you skip 3rd and go straight to 4th? Its 1 to 1. is there any oil in the box? Or diff? If the box bearings are gone gear selection would be tricky as 1 or both shafts will drop causing meshing issues, almost certainly would be making some odd noices. I think duff engine / diff

Edited May 8, 2015 by DanE

[chris n]

S7 should have U/J's at both ends of the prop and be a one piece unit, only the very early kits had the U/J at the diff end and the rubber coupling at the gearbox end this was a modified donor part.

If it has the rubber coupling fitted I would change the prop out no matter what as when they let go its not pretty.

 

If you have the prop off the car put the box into 3rd or 4th gear and check the amount of play on the output shaft there should only be a very small amount of play to allow for the back lash on the bearing.

 

My mate had a similar thing on his cobra car would do 40mph at the wheels but it was in top gear with the speedo reading 60mph. Turned out to be the main shaft bearing on the output shaft and needle roller bearing on the input shaft were both shot.

[theduck]

I take back everything I said about it not being the brakes biding. They are, massively.

[sj-bradley]

Before you dismantle the brakes, take a photo and then check that the pad are on the right way up and possibly even on the right side.

 

I thought it had to be them from your earlier description of the problem. Nowt like not being able to see wood for the trees in the way!

 

 

Simon.

[Thrashed]

Hi Stu

 

Could it be a brake shoe popped off the retaining springs and periodically binding. Might be an easy thing to check?

[richyb66]

Thx chris, I think it must have the early prop with the rubber doughnut at the box end which would explain why the prop doesn't droop down when it's unbolted from the diff.

[richyb66]

Binding brakes won't help but surely the effect would be in all gears? If you're running it up with the wheels raised, can you remove the drums and refit the wheels (to keep some inertia) and try it. Without braking, obviously.

[theduck]

The effect was in all gears, I think just more noticeable in the higher gears.

 

The prop is definitely a rubber doughnut type.

 

I'll try running it up tomorrow with the wheel back on but drum off.

[Guest 2b cruising]

If on test you had already had the brake test, it should have failed on brake bind.

If the brakes weren't binding on the brake test but are now, it points to either something like a partially siezed cylinder, blocked brake line, faulty handbrake. Did you pull your handbrake on really hard at the end of the foot brake test so this was on its maximum.

Could be trapped able or faulty mechanism.

[sj-bradley]

I think it sounds like brake pad grab.

 

Brake shoes are usually trailing type. The drums have only one cylinder so one of them is the leading type. They must be on the correct way round or else you can get this brake snatch phenomenon.

 

If you have put these on the wrong way round, the drum could snatch the brake pad pulling it hard on into contact. It then drops out when the wheel stops until you get it spinning up again.

 

This was why you thought the brakes were free when you spun them by hand.