Replaced Spigot Bush recently?

[JJC]

Has anyone replaced the bush in the end of the crankshaft (part number 047246) and used it for long enough to be confident it's OK?

[Menno van Rij]

I've replaced it a few months back, but I haven't driven the car yet (restoration!). I'm interested: what's the reason of your question?

 

Menno

[Rhodri]

I also replaced mine but haven't used it yet. The first one I bought was too small and was loose in the crank, the second was fine. I soaked it in oil for 24 hrs before I fitted it.

 

Rod

[88V8]

If it's made of phosphor bronze to the correct dims, why not.

Rhodri has pointed up the most important factor in long life - soak it in clean engine oil for at least 24 hours and preferably two weeks.

 

Ivor

[JJC]

I've replaced it a few months back, but I haven't driven the car yet (restoration!). I'm interested: what's the reason of your question?

 

Menno

Thanks for your reply. Reason for asking is because I had difficulty when purchasing the bush which goes between the two shafts inside the box so I had to get one made when I was rebuilding the box. I'm just about to put the box back in and just wondered if the crankshaft bushes which are available are known to be to original tolerances and spec. (I have to replace it because I think it was these two bushes which caused the unpleasant noise in first gear that made me take the box apart). The crankshaft bush doesn't have to be tight, originally I think were Oilite (a grade of phosphor bronze I think) but obviously need to be made to the right tolerances.

[Rhodri]

I think I bought the good one from TRGB?

 

Rod

[JJC]

I think I bought the good one from TRGB?

 

Rod

Thanks - very useful

[Menno van Rij]

Has anyone replaced the bush in the end of the crankshaft

 

Back to the first part of your initial question: I also soaked the bush in oil for a few days. After that, I filled it with oil, closed off one end and applied pressure. That way, I was sure that the oil was soaked into the bronze.

As far as I know, this stuff is called sintered bronze (well, in Dutch it is 'sinterbrons') and that it's capable of absorbing oil. which it did. At this moment there's a discussion in the Dutch Saab 96 forum about bronze (sintered) bushes too! All advise given on that forum is the same as all advise given above. There's only one interesting advise, though: one Saab owner spend most of his working life on a ship on the ocean. Most of the time they had no time to wait for the oil to be absorbed into the bronze, so they cut corners here. He states that they used grease: totally covering the bush in grease, then melting the grease 'au bain marie' (using some sort of melting pot), that way the grease is absorbed into the sintered bronze.

 

Menno

[Don Elliott]

From 1958 to 1972, I drove my 1958 TR3A a little more than 80,000 miles. Then it sat 15 years un-used till 1987 when I started my restoration. It was 1990 when I finished but I had not changed the pilot bushing in the rear of the crankshaft. About 43,000 miles later, I had the engine apart again to install a new modern rear main bearing oil seal. I changed that pilot bushing. I immediately noticed after putting it back together that the transmisstion was a lot smoother. The new bushing supports the far front end of the input shaft to the gearbox and the old worn bushing caused this front end of the input shaft to be free (off axis). The new one aligned that shaft centrally and for the few pennies that a new bushing costs, I'd recommend it.

 

Since then, I've driven another 57,000 miles and it's all still smooth - ie. still centrally aligned.

 

The bushing is made of porous sintered bronze (perhaps using powdered metal technology to achieve the porosity). The bushing comes loaded with oil in those tiny pores, but I soaked mine in oil for about a month which I was doing other things. I wanted to really ensure that the pores in the bushing were full of oil.

[JJC]

Thanks - very useful

 

I'm told that the acceptable (current) manufacturing tolerance is +/- 4 thou (actually these days it's metric but thou relate more to the TR world for me). 4 thou under in an o/d of 1 inch sounds a lot for this bush. I wonder how many sources currently are remanufacturing? Incidentally I don't think soaking in oil has anything to do with it at all and manufacturing tolerances have everything to do with it (although it obviously needs some lubricant). But then I'm not an engineer, I just had a lot of Meccano as a kid. Anyway, I'm going to buy one and if it doesn't feel right when I get it then I'll just have to find a way of making a more suitable one.

By the way, whilst we're in that part of the transmission, when replacing the flywheel you might have spotted that both stretch and non stretch bolts have the same part number in the Moss catalogue (at least they do in mine, perhaps it's out of date).

[Rhodri]

Remember that the only time that the shaft is revolving in the bush is when you have your foot on the clutch. Otherwise the clutch is locked and the gearbox shaft and the crankshaft turn as one, meaning that their is only movement in this bush for a few seconds at a time- unless you sit at the lights etc, in gear, and with your foot on the clutch

 

Rod

[vivdownunder]

JJC, when you get your new spigot bush, check the tolerance by slipping it over the end of your gearbox input shaft.

 

Better to know if it's the right or wrong tolerance before pressing it into the flywheel.

 

The reason for a higher I/D tolerance than you'd expect is for ease of fitting the gearbox.

 

Early gearboxes didn't have a lead-in chamfer on the input shaft, and those gearboxes would be almost impossible to re-fit into a really tight spigot bush.

 

You'll need to use the clutch plate aligning tool when refitting the pressure plate. Check that the aligning tool can be removed easily before you torque up the pressure plate bolts. Then fitting the gearbox should be a breeze.

 

Regards,

 

Viv.

[JJC]

JJC, when you get your new spigot bush, check the tolerance by slipping it over the end of your gearbox input shaft.

 

Better to know if it's the right or wrong tolerance before pressing it into the flywheel.

 

The reason for a higher I/D tolerance than you'd expect is for ease of fitting the gearbox.

 

Early gearboxes didn't have a lead-in chamfer on the input shaft, and those gearboxes would be almost impossible to re-fit into a really tight spigot bush.

 

You'll need to use the clutch plate aligning tool when refitting the pressure plate. Check that the aligning tool can be removed easily before you torque up the pressure plate bolts. Then fitting the gearbox should be a breeze.

 

Regards,

 

Viv.

Thanks for very useful tips, the tolerance quoted was for the o/d I don't know what the i/d tolerance is. Could be that those racing their cars don't suffer because they're clutch is either in or out? I'll follow advice on alignment tool.

Best regards

JJC

[Don Elliott]

For the last two pilot bushes I installed (on my 1958 TR3A as well as the 1960 TR3A I restored), the outside diameter was a fairly loose "slide fit" into the end of the crankshaft. That is, there was clearance. I didn't worry about this. I don't care if the OD of the bushing rotates in the crankshaft or if the end of the input shaft rotates inside the ID of the bushing. It is lubricated both ways.

[Dick]

Remember that the only time that the shaft is revolving in the bush is when you have your foot on the clutch. Otherwise the clutch is locked and the gearbox shaft and the crankshaft turn as one, meaning that their is only movement in this bush for a few seconds at a time- unless you sit at the lights etc, in gear, and with your foot on the clutch

 

Rod

 

And theoretically there should be no load on it.

 

I have not seen mine since 1986....I turned mine up out of phospher bronze.

 

I seem to remember that they are a fairly loose fit.

 

Only sintered bushes will take up oil in the soaking process as they are porous.

 

A good mod. to do is to drill a 30mm hole in the bottom of the bell housing directly below the clutch cross shaft pin....If it shears you stand a chance of getting it out with a long socket extension and a socket that I heated up and forged to suit the square head of the pin. and thereby replacing it without gearbox removal. Even if it won't then as long as you have the spare pin, gearbox removal at the roadside is not that much of a challenge if you are forced to do it..

 

I always have carried a spare pin....but have not had one break yet......why did I say that!!!!!!!!

 

Over the winter I always try to overhaul something, on the principle that fixing before breakage is part of the maintenance program...

 

Last year was steering box rebuild...year before front suspension...rear springs before that.

 

This year I may pull the gearbox and replace the clutch....which, although not slipping has suffered 40,000 mlies of enthusiastic driving.... it will be interesting to examine the bush.

 

Regards Dick.

[RogerH]

Hi Dick,

I had similar thoughts about the 30mm hole.

I haven't done it yet but I thought that I'd give the tapered pin 50K miles and then remove/replace it without G/B removal.

The last pin had a nice crack developing at about that mileage.

Wire locking the new pin should be interesting.

 

Roger