rear gearbox mount

Simon Bolton · Post by **Simon Bolton** » Sat Jul 03, 2010 4:56 pm

Hi All.
I've been baffled for a while as to a knocking that I thought was the front suspension.A friend on this forum suggested that I should look at the gearbox mount.Not knowing how it should look I tweaked up the stabiliser a couple of turns and hey presto most of knocking had gone( Is'nt it strange how noises travel around a car).My dilemma is that it is not clear in the parts books how the finished unit should look.On mine ('66 2+2)the pin comes down through spring ,rubber and bracket- then there is a cup which is very loose sitting on a large split pin.What is worn or do I replace everything and how.I know that the stabiliser should not be taking any weight so I should do this soon.Incidentally,I had the stabaliser set at the point that it was just nipping up.Is this correct?
On another tack has anyone any comments on the sealing of spoke ends with silicone so that tubeless tyres can be used and who does it.I'm fed up with tubes going just because of rubbing inside.Maybe doing over to 'D'type wheels is the answer.
Many Thanks Simon

daverawle · Post by **daverawle** » Sat Jul 03, 2010 5:16 pm

On another tack has anyone any comments on the sealing of spoke ends with silicone so that tubeless tyres can be used and who does it.I'm fed up with tubes going just because of rubbing inside.Maybe doing over to 'D'type wheels is the answer.

Can't help on the gearbox mount Simon but Ray Livingstone off JagLovers sealed his wheels successfully; I seem to remember he used polyurethane sealant. If you go to JLs you can search the archive using his name and tubeless or some such phrase. The thing you need to ensure is that the rim profile on your wheels is the correct form to properly seal a tubeless tyre. I have a Dayton tubeless wheel to hand so can take a picture of how it looks if you want.

Dave

Post by **1954Etype** » Sat Jul 03, 2010 5:26 pm

Simon Bolton wrote:Hi All.
I've been baffled for a while as to a knocking that I thought was the front suspension.A friend on this forum suggested that I should look at the gearbox mount.Not knowing how it should look I tweaked up the stabiliser a couple of turns and hey presto most of knocking had gone( Is'nt it strange how noises travel around a car).My dilemma is that it is not clear in the parts books how the finished unit should look.On mine ('66 2+2)the pin comes down through spring ,rubber and bracket- then there is a cup which is very loose sitting on a large split pin.What is worn or do I replace everything and how.I know that the stabiliser should not be taking any weight so I should do this soon.Incidentally,I had the stabaliser set at the point that it was just nipping up.Is this correct?
On another tack has anyone any comments on the sealing of spoke ends with silicone so that tubeless tyres can be used and who does it.I'm fed up with tubes going just because of rubbing inside.Maybe doing over to 'D'type wheels is the answer.
Many Thanks Simon

Hi Simon, I am pretty sure that you shouldn't have a split pin as this was used as an assembly aid. It restricts the movement of the rear of the gearbox (happy to be corrected but I have never used one and never had a problem). There are two rubber mountings. Oneis a rubber cup and the other a bobbin which the gearbox pin goes through. These rubbers fail because they become contaiminated with oil (does anyone do a poly one?).

Hope this helps
Angus

christopher storey · Post by **christopher storey** » Sat Jul 03, 2010 5:32 pm

Simon - I am a bit surprised that you are wearing through tubes. Your wheels should have a rubber band, about 1.5 mm thick and 1.5 inches/ 40mm wide, which fits tightly over the well in which the nipples for the spokes are fitted. If you have not got these, or they are shagged out , it would explain your problem . Available from Longstone Tyres

daverawle · Post by **daverawle** » Sat Jul 03, 2010 6:21 pm

Simon, another thought on the tube problem - have you removed ALL traces of any paper labels that are stuck on the inside of the tyres?

Dave

Simon Bolton · Post by **Simon Bolton** » Wed Jul 07, 2010 2:09 pm

Thanks for replies guys
First rear engine mount.Angus,you have worried me now and,not wanting to doubt you but I'd appreciate confirmation from others because ,having looked at the illustration in the spares bible, you're right that there is no split pin but what is attached to what or is it just 'floating'.the order from the top appears to be
cup with hole in it
rubber bush ?
pin (with hole in bottom presume for 'in transit' split pin)
spring(with bobbin in it?)
spring centre bush
spring seat
bracket
I am baffled.By having the split pin in am I causing the knocking and putting undue strain on the assembly?If I take it out,surely the whole thing will bounce around on an untethered spring. Help.
As to tyres
yes I have taken all labels off as they caused first two punctures and yes I do have bands over the spoke ends but thanks for suggestions.
I've had a chat with the guy who runs my local tyre fitters and,come the winter,we are going to have a go at siliconing up a wheel as best we can,refitting the tyre and giving it a whirl-nothing ventured etc.Watch this space!
Thanks for your time
Simon

Post by **1954Etype** » Wed Jul 07, 2010 2:19 pm

Simon Bolton wrote:Thanks for replies guys
First rear engine mount.Angus,you have worried me now and,not wanting to doubt you but I'd appreciate confirmation from others because ,having looked at the illustration in the spares bible, you're right that there is no split pin but what is attached to what or is it just 'floating'.the order from the top appears to be
cup with hole in it
rubber bush ?
pin (with hole in bottom presume for 'in transit' split pin)
spring(with bobbin in it?)
spring centre bush
spring seat
bracket
I am baffled.By having the split pin in am I causing the knocking and putting undue strain on the assembly?If I take it out,surely the whole thing will bounce around on an untethered spring. Help.
As to tyres
yes I have taken all labels off as they caused first two punctures and yes I do have bands over the spoke ends but thanks for suggestions.
I've had a chat with the guy who runs my local tyre fitters and,come the winter,we are going to have a go at siliconing up a wheel as best we can,refitting the tyre and giving it a whirl-nothing ventured etc.Watch this space!
Thanks for your time
Simon

Simon, the gearbox needs to 'float'. By using a split pin, you are virtually locking it in place as the spring will be under more tension than it should be. This could be causing your knocking. I did a bit of research on this as Hutsons and I had a long debate over whether the pin should be fitted. Apparently, they are for some models (XJ IIRC for example). If you do a search on Jag-Lovers, there is more information than you will ever want. How about a quick poll, who has a standard gearbox and a split pin fitted?

Simon Bolton · Post by **Simon Bolton** » Wed Jul 07, 2010 4:33 pm

Angus you appear to be right(not that I doubted it).I've just got on jag lovers and there is mention of this and likened to transport of a washing machine-harsh but fair.I must say though I don't find it an easy site to negotiate.I am going to take it out (with much trepidation) and wait for the bang!
I would though appreciate an explanation of the setup if anyone is so inclined.
Many thanks Simon

christopher storey · Post by **christopher storey** » Wed Jul 07, 2010 9:40 pm

Simon : the overall setup is such that in fact the rear spring with its rubber accoutrements does little other than give support to the minimal load at the tail of the gearbox , and at the same time provides some NVH insulation by reason of the rubber parts. The centre of gravity of the 680 lbs or so weight of the whole assembly is concentrated just to the rear of the midpoint of the engine, at about the no3 cylinder position ( numbering from the back) and is therefore about 2/3 of the way forward in relation to the whole length.Thus by virtue of the lever arm effect, the load on the spring is relatively speaking much lighter - hence the fact that the spring is not an enormously stiff one. In addition , any appreciable upward or downward movement of the assembly is resisted by the stabiliser rod which runs from the top of the bellhousing to the front bulkhead

ChrisC · Post by **ChrisC** » Thu Jul 08, 2010 2:57 pm

One thing to remember is that the gearbox stabiliser mounted to the bulkhead is not supposed to be load bearing like an engine mount. It can be adjusted so that it is a close fit but it is not supposed to lift the gearbox up.

If you tighten it up too much you run the risk of cracking the bulkhead bracket (seen this on a couple of cars)

Cheers

Chris C

christopher storey · Post by **christopher storey** » Thu Jul 08, 2010 4:03 pm

Yes indeed, Chris C. Only on Sunday we had to lower an engine in a 2+2 by about 10mm because it was being held aloft by the stabiliser!

Dave K · Post by **Dave K** » Sat Jul 10, 2010 10:40 pm

My original 3.8 being an early car has the two rubber mounted spools which hold the gearbox rock solid to the support which in turn is bolted to the floor of the car, strange how Jaguar then decided that it should float?
My new CJ 5peed box is also bolted hard down via a rubber support to gearbox support plate.

The other thing about the engine stabiliser is the adjustable support is on the bottom so after everything is right and level you screw the bottom plate up to the mount so the recess fits inside then drop the top section in and put a nut on the threaded section to hold it all together at least that's how it is on the 3.8's not sure if this is the same on later cars but I would have thought so.

Dave

christopher storey · Post by **christopher storey** » Sun Jul 11, 2010 9:36 am

Dave K : yes, the 4.2 is the same, but what people have a habit of doing is leaving the bottom one too low and then screwing the top one down too far thus raising the engine, and overloading the bulkhead

Simon Bolton · Post by **Simon Bolton** » Tue Jul 20, 2010 7:12 pm

Thanks Everyone
Certainly the split pin should not be there-far fewer 'bad' noises but I think that I will replace spring and bush come the winter because it still is'nt quite right.I think this bit was thrown together without too much knowledge.
Thanks again Simon

Dave K · Post by **Dave K** » Wed Jul 21, 2010 5:24 pm

Thanks for letting us know Simon. I was past your place today and tomorrow on the way to Aylesbury but not in the E this time the Astra super sport.

Seems odd that Jaguar start off with a solid gearbox mount like my '61 had, the two rubber spools and then they go to a spring mounted support.
My new CJ 5 speed has a solid oblong neoprene type support.

Dave

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