Transmission mounts and oil pressure switches

[bobdisk]

In the last few journeys there has been a lot of rattling and banging coming from the rear when I go over rough roads and potholes. I think perhaps one or more of the primary's rubber mountings have failed. I have yet to look under the covers to confirm. Is it possible to replace them without removing the primary completely? 

[andrew]

As I remember when I removed the primary unit on my 33 the rubber supports appear to be splashed in oil from the transmission unit. As I understand it, when the transmission oil is drained and changed a small amount is spilt and when the oil warms up during driving oil vapour escapes through the vent on the top, which in turn then soaks into the rubber mountings. I could be wrong, though!

The other factor that might be causing the vibration could be the nylon bushes that fit onto the cradle rods, which in turn slot into openings in the car's frame. These circular holes are horizontal and allow the primary unit to slide into these holes to support it. The nylon bushes slide over the two rods on the primary unit, making a "snug" (=bloomin' tight!) fit, preventing vibration. I apologise if my explanation doesn't make sense, but examination of a workshop book or manual will clarify things.

To gain access to these one needs to remove the cover, slacken off the belts, mark the vacuum pipes and remove them, remove the belts and disconnect the handbrake cable. Open the access panel just forward of primary unit (a small rectangular panel, secured by a self-tapping screw) and store it and the screw. Remove the gear selector lever. Place a jack under the base of the primary unit (a block of wood between the jack & primary unit is a good idea) and s-l-o-w-l-y slide the primary unit towards the rear of the car.

Now the hard part......As if it's not been tricky enough already! By now you'll have worked out that the primary unit sits in a cradle, which is, in turn, supported at the front by two rods that slide into openings under the rear seat and at the rear it's bolted to the frame. These two bolts also have nylon bushes surrounding them, again to reduce vibration. With the cradle supported undo the bolts then slightly lower the rear of the cradle and slide it backwards, thereby releasing the two rods at the front from their apertures. The cradle and the primary unit within it should now come away on the jack.

I'll explain the next part later!

Right then, that's YOUR Saturday morning mapped out.......

[bobdisk]

Oh, that will take some time! I will look under the covers tomorrow (Sunday) see what I can find. I did get 2 nylon bushes for the blue one, but never used them, Still have them. Its a good excuse to improve the change lever, there is too much play in it.  

BTW, idle seems ok, once its hot. The accelerator/low switch has next to no effect on idle speed. Careful use of the choke from cold to hot.

[bobdisk]

It seems the nylon bushes have worn away and I can lift the cradle. You can see the screwdrivers go in where the bushes should be. The rubber mounts appear to be ok, they are not soft, as you would expect if they were contaminated. Is it possible to replace the bushes without dismantling the whole thing? Theres a lot of black dust, from the belts. A lot considering it was clean, and i have not done very many miles. Could the belts be too tight?

[andrew]

Bob,

Yes, the places where the screwdrivers are pushed in are precisely where the nylon bushes go. As for changing them, I think the rear ones could be changed by undoing the nuts & bolts and then lowering the rear part of the cradle a little, pushing the new nylon bushes into place and lifting the cradle back onto place by using a jack. To change the front ones you need to move the cradle rearwards, and the rear support brackets need to be removed to facilitate this.

The primary unit weighs quite a lot, as we know from when we man-handled one into the rear of my Subaru at the last A.G.M.! I would advise having a friend nearby when you undertake this, just in case!

As to the dust building up in and around your primary unit, looking at the picture I think there's an excessive amount and maybe a clean-up would be advantageous. Having the belts too tight would not help the car's acceleration and would strain the clutch, but I can't see how it would cause the build-up of dust you've found. Once you've replaced the nylon bushes check the pulley gaps (1mm for run-in belts, 1.5mm for new ones) and see how it runs.

[dafman50]

You can slide primary back supporting on jack and replace nylon bushes.the dust will probes be from the old belts as hands up I did not clean off underside when fitted.

[bobdisk]

dafman50, Could both front and rear bushes be done on the 9/10 Sept open days, one or both. If both days, I will stay overnight at a local hotel.

[dafman50]

Yes mate I can do for you .on both days just incase we hit issues.

[dafman50]

Yes Bob both can be done on day .but best if possible allow both days in case of issues

[bobdisk]

All back together, It drives a lot better using the carb from the original engine. I think the vacuum ratio change is working. It increases idle revs slightly with the brakes/low ratio switch. BUT, one of the push rod tubes, or something there, (on the left of the car) has not sealed, and it still leaks like a sieve!! So its all got to come apart again, groan! What else could it be? I have changed the oil pressure light switch, so its not that. Which side did you find had leaked, I thought it was drivers side of car.

[bobdisk]

I took the front of the car and the cylinder covers off and ran the engine for a couple of minutes. It turns out it was the replacement oil pressure light switch squirting oil out. Someones in for an earful!

[Richard DAF Webmeister]

I need to replace the oil pressure switch on mine.

Were you able to change yours fairly easily? I.e. without having to remove pipes and cowls and things?
I keep looking at how low down and out of reach it is, that I keep putting the task off!

[bobdisk]

The pressure switch is an awkward thing to change, you cant get a spanner on to it with the cowls in place. I took off the front bumper (2 bolts), the front panel (10 bolts), the fan (3 nuts) and its housing (3 nuts and the coil), then unclip the cowls, then there it is!! Once that lot is off, you can get a spanner on it easily. A socket will not go onto it because it catches on the cylinder. It took about 2.5 hours start to finish. It was not difficult as I had had it all apart a couple of days before to replace the push rod tubes and seals. The replacement switch came off another engine. I put a couple of turns of PTFE tape around the threads, to make sure it did not leak. The old one was intermittent open circuit, so the light did not always work. The terminal is bent to clear the cowl, and allow the connection. And oil was leaking out of the terminal because of the bend. The replacement has a screw terminal so there is a greater clearance to the cowl.

[bobdisk]

Has your switch's terminal been bent like this? look to see if the body has cracked, that starts it failing.

[Richard DAF Webmeister]

Thanks for the description and photos. I guessed it would involve much dismantling - I might get around to it one day.
Meanwhile, I have a lovely brand new oil pressure switch - supplied by Steve in the Club - sitting on the passenger seat, waiting for its fitting!

I've no idea if my terminal has bent or whatever - I can't get close enough to see!!

[bobdisk]

Look down by the dipstick between the block and the cowl, if the wire in the spade terminal points to the front of the car, its bent, as on the old switch I have placed in the pic beside the new switch. They did that to get the wire on to the connection in that limited space. The switch with the screw terminal does not need as much space.  If the oil pressure light does not work properly, I would make it a priority job. I am thinking of trying to put in a pressure gauge.  What type of switch have you got?

 .

[bobdisk]

Anyone know if there is a way of changing or modifying the threads title? We have here gone off the title of "transmission mounts" to "oil pressure switch". It would be nice to reflect both subjects this in the title.

[Richard DAF Webmeister]

Oct 27, 2023 16:29:43 GMT bobdisk said:

Anyone know if there is a way of changing or modifying the threads title? We have here gone off the title of "transmission mounts" to "oil pressure switch". It would be nice to reflect both subjects this in the title.

Yes! I was thinking the same.
When I set this site up many years ago, I wanted it to be like a classified adverts section of a newspaper.
I.e. have a subject then discuss within it.

Sometimes we get diverted.

Job done! (Not the oil switch - it'll have to wait until the car next goes in for a "MoT type checkover". I haven't got the tools or the dexterity to pull things apart. Actually, that's not quite true - I can pull things apart but rarely get them together again, or lose my temper and break something else in the process.)

[bobdisk]

Thats good , thanks. Now we look forward to your switch!! If I think of a way to put a gauge in, I will publish!!