Rear engine support fully compressed

[skiday]

As you most of you know, I am converting my series 1.5 from auto to manual. Concerning the rear engine/gearbox support. I have adapted the old plate to move the spring forward about 2 inches, but apart from that, it is as standard. From picking them up, I would guess that the auto box is quite a bit heavier, or at least as heavy as the replacement LT77 (from an XJ6), but now that I've fitted it all in, the spring has compressed fully as if it can't take the weight. I have a new rubber centre on order, but shouldn't that be like a bump stop? Shouldn't the spring itself be capable of taking the weight of the engine and gearbox, or is this a sign that I have something else amiss re fitting of the engine/gearbox/prop shaft? When I was at the point of trial fitting, it supported it no problem, but now the prop is connected, so I suppose that could be the difference. Are there upgrades of spring available?

Thanks

Andrew

[christopher storey]

Have you re-adjusted the engine stabiliser? It sounds as though this could be pushing the engine and box downwards. Incidentally, the LT77 is notably heavy at about 105 lbs, but I would not have thought it differed much from the autobox, and certainly I would not have thought it would be significantly heavier. Another candidate for trouble is the fact that you have moved the mount forwards. The vertical clearance may as a result be rather different from what was expected

[PeterCrespin]

Have you re-adjusted the engine stabiliser? It sounds as though this could be pushing the engine and box downwards. Incidentally, the LT77 is notably heavy at about 105 lbs, but I would not have thought it differed much from the autobox, and certainly I would not have thought it would be significantly heavier. Another candidate for trouble is the fact that you have moved the mount forwards. The vertical clearance may as a result be rather different from what was expected

All good points - the last one especially.

The BW auto is much heavier than the LT77, which is around the same as the 4-synchro long version. I frequently lift/move the latter but the auto is a monster. Getrags or T5 boxes are featherweights compared to all the above, as is the Supra box.

There are rubber cups on the spring top and bottom but the central rubber is not a bump stop - it's a vertical guide for the pin to stop it rattling or moving side to side as it bounces up and down (within the confines of the movement allowed by the stabiliser bush)

Moving the mount forward will put more load on it.

There are different grades of spring for saloons, E-types etc. Not sure which is stiffest. Bit of trial and error or side-by side compression required. Obviously this does all presuppose there is no contact between box and tunnel. The LT77 bell housing is different from all the Jag manual bells but since it was used in the same XJ tunnel as the BW auto, it must fit an BW auto E-type.

Pete

[skiday]

Thanks for the replies.

In answer to Christopher - The mid point stabiliser has not been connected up yet as I know it should not take any of the weight, and in answer to Pete - I have made a new custom tunnel which is higher, and the new box has sufficient room to move. Given that we agree that the LT77 is lighter that the BW, moving the mount forward be 2" seems perhaps to be an unlikely cause.

I've just had a thought what it could be... The bolt/pin that is in the centre of the spring that came off my BW box did not fit into the LT77. The hole in the bottom of LT77 is metric (M10 I think) so I used a length of M10 bar which is threaded all the way top to bottom. What Pete said about bouncing up and down made me think, perhaps the engine/gearbox moved downward and the threaded bar caught on the hole in the plate and prevented it from going back up. I was sure that when I first put the plate up it supported the gearbox, but it was when I came back to it later that it had gone down, and this theory would fit in with that. I've just looked up the SNG catalogue and the pin for the XJ6 is not listed, but I could try grinding off the thread where it is not needed. I will try again tomorrow to jiggle it about and see if I can work it out.

Night night

[PeterCrespin]

. The hole in the bottom of LT77 is metric (M10 I think) so I used a length of M10 bar which is threaded all the way top to bottom. What Pete said about bouncing up and down made me think, perhaps the engine/gearbox moved downward and the threaded bar caught on the hole in the plate and prevented it from going back up. ... I could try grinding off the thread where it is not needed.

Umm, the gearbox is restrained laterally by that pin passing through a central rubber bobbin with the spring n'est-ce pas? How many days did you expect that rubber to last with an M10 stud sawing away at the inside of it?

I'd at least try to sleeve it on get yourself a decent M10 plain shank bolt and saw the head off after fitting, rather than use studding. If you think you might need to remove it some time in future file a couple of flats on the end and use anti-seize.

Meanwhile, if I understand you correctly, you think the 60 degree thread flank is hanging up and keeping the strong spring compressed? If so there must be major misalignment for the thread to be pressing hard enough on the edge of the mount, metal to metal and I'm not sure how you'd expect to fit the rubber bush?. It all sounds a bit odd to be honest, or I'm misunderstanding something.

By the way, when engineering your new mount have you ensured the centreline of your output flange is at the same height as the original? Thinks can get iffy fairly quickly if there much change in the driveline alignment.

[skiday]

What I wrote last night I did at half one in the morning so I obviously wasn't thinking straight. By the time I woke up in the middle of the night I knew it couldn't be that, as the bolt passes through a whopping big hole and has a huge washer/retainer disc on it, and it is now lined up extremely well. Good point about the threaded bolt sawing at the rubber. I will sleeve it or find a solution to that.

I thought by the time I got up I would be able to retract last nights ramblings, but you're too quick for me!

With regard to the last paragraph about output flange etc., I think so, but I will ask my mechanic to check, as I didn't really understand all the technical terms you used.

Andrew

[skiday]

It?s a strange world this virtual world where people talk to each other without really knowing much about them. It may help therefore, to fill in a little background to help you advise me, should you wish to that is. As the expression goes; this is where I?m at?..

Firstly, I am only a keen amateur; I have no formal mechanical training, although I always worked on my own cars, and have built a Beauford kit car (if I may say ? to a high standard for a kit car). See here; http://www.beaufordweddings.co.uk/page8.html . This is my first (and I would imagine my only) E-Type. Therefore I may not understand complicated explanations, but I am constantly learning.

Secondly, I was only an observer at the strip-down. The mechanic who did the work is no longer with me, so I am not certain of how things came apart, or where some bits are from.

Lastly, the mechanic who is helping me now (as and when he can find me time) has worked on E?s, but that was some time ago, so his knowledge base in not extensive, but his is a very accomplished mechanic and metalworker.


Anyway, back to the matter in hand. The central rubber I ordered from SNG didn?t arrive today, but then there?s no guarantee that it?ll be the right part anyway, (they sent me an alternator belt and it was the completely wrong one). I found a rubber cone in my box of bits, which I think is the original, but couldn?t be sure if it was from mine or came with the LT77 (I think the former), I expect you would know right away;



I re-assembled it all again today and I think that I previously had too great an expectation of how much height the spring would retain. I see from my strip-down photos that it was compressed to 1? inches when under the auto. I was relying on the spring to lift the engine/gearbox higher to where it needs to be (as determined by the height of the mid-point stabiliser bolt), but of course, this is an alien gearbox to the E, and there is nothing to say that the bottom of the gearboxes are at the same level. Therefore in order to get the gearbox up to the required height I think I simply need to place some spacer washers between the spring cap and the gearbox. This will bring the centreline of the output flange to at the same height as the original (as you say). It is clear now that when I said that the spring was fully compressed that that was a mistake, it was just compressed more than I expected it to be. This is what it looks like now with the centre rubber in;



Cheers

Andrew

[1954Etype]

Hi Andrew, it is difficult when you deviate from the standard trying to get parts to fit correctly. (Thats why I'd never attempt a custom or kit car - too much figuring out to do).

On the standard 4.2 S1 manual gearbox, the rear mounting is not locked down. THere is a stud on the rear of box (where you have a thread) and this goes through the centre rubber bobbin type mount. This is not locked down and allows the box to 'float'

[christopher storey]

Oh, ouch, ouch, ouch!! That nut should not be there in the first place, and even if it were supposed to be , is at least 8 threads ( which is equivalent to , give or take , 1/2 inch) higher than it should be if the spring were to assume a natural position. I think if you were to remove the nut, you would find that the geometry would be much more normal

[skiday]

The nut is in that position because the spring IS sitting in its natural position; it is only finger tight. The bar is that much longer simply because I cut it to that length. If I had cut it shorter it wouldn't protrude so much. When I am happy with the final fit I can then remove any excess threaded bar and fit a locking nut so that the bar does not compress the spring. If anyone knows where I can get the proper pin to fit the LT77 please let me know, but my old one doesn?t work, so I can?t think of a better solution.

I am still hopeful that some one can tell me if they recognise the round rubber block in the photo as the correct item for the centre of the spring or not.

Andrew

[PeterCrespin]

The round rubber bobbin does not appear standard. certainly for the normal E-type mount. The LT77 uses a completely different system and it looks like the XJ6 part, let alone apprearing distinctly secondhand, whatever its provenance. It will be fluke rather than judgement if things turn out right using a mish-mash of parts, sorry.

Meanwhile, you are misunderstanding the rear mount. How do you suppose the car would ride if the suspension were unable to extend beyond the mid-laden position? Terrible. Same goes for your engine/gearbox unit. They did use a pin as a restraint during transit at one time, but this was removed before sale. Its purpose was rather like the transit restraints fitted to the average washing machine: to stop the heavy suspended tub bashing inside the casing on rough roads during the journey from factory gate to end user.

Please, whatever parts you end up using, having set it up with that piece of mild steel stud get yourself a decent-strength plain shank M10 bolt for pennies. It should be threaded far enough to bottom out in the hole - which it is almost bound to be - but not so far as to present a threaded surface to the inside diameter of the correct rubber bush. Ideally you should file or turn off the first couple of threads down to the base circle diameter or slightly below, so as to leave a plain section to be sure it reaches the base of the blind hole.

After you screw it home, measure to a point about half an inch beyond the base of the mount and cut it off. If it turns out your gearbox is banging the tunnel, or your output flange is too high or too low, you might have to rinse, lather, repeat until you get it right. Such are the tribulations of special-building and they are not for the faint-hearted. Good luck.

Pete

[1954Etype]

The round rubber bobbin does not appear standard. certainly for the normal E-type mount. The LT77 uses a completely different system and it looks like the XJ6 part, let alone apprearing distinctly secondhand, whatever its provenance. It will be fluke rather than judgement if things turn out right using a mish-mash of parts, sorry.

Meanwhile, you are misunderstanding the rear mount. How do you suppose the car would ride if the suspension were unable to extend beyond the mid-laden position? Terrible. Same goes for your engine/gearbox unit. They did use a pin as a restraint during transit at one time, but this was removed before sale. Its purpose was rather like the transit restraints fitted to the average washing machine: to stop the heavy suspended tub bashing inside the casing on rough roads during the journey from factory gate to end user.

Please, whatever parts you end up using, having set it up with that piece of mild steel stud get yourself a decent-strength plain shank M10 bolt for pennies. It should be threaded far enough to bottom out in the hole - which it is almost bound to be - but not so far as to present a threaded surface to the inside diameter of the correct rubber bush. Ideally you should file or turn off the first couple of threads down to the base circle diameter or slightly below, so as to leave a plain section to be sure it reaches the base of the blind hole.

After you screw it home, measure to a point about half an inch beyond the base of the mount and cut it off. If it turns out your gearbox is banging the tunnel, or your output flange is too high or too low, you might have to rinse, lather, repeat until you get it right. Such are the tribulations of special-building and they are not for the faint-hearted. Good luck.

Pete

Pete not sure you are correct when you say it was locked down with a pin for transit purposes. I think it was for assembly of the car. Have you tried to bolt the rear mounting to the body while trying to compress the spring? Doable but really difficult. Have you also tried to pull out the locking pin with the exhausts in place? Again, difficult to do. (I've done both over the years!). I believe they were assembled with the pin in place then it would have been removed. (How much more banging about would the mount have in transit than it wouldn't get during normal road use?).

[skiday]

I can see what you mean. Certainly I agree that the box has to be allowed to move up and down and that the nut would prevent this. So if the nut is omitted then the washer must also be too, meaning the centre pin is left free in the middle of the inch and a half hole of the support plate (although fitting snugly in the middle of the centre rubber block). I really need to see a mount in situe to see what it should look like. Like I say, I didn't see it during the strip-down, so I don't know what it should be like. I have access to a V12 (if I can jack it up) would that be roughly the same?

In the original centre pin, what was it that the hole at the bottom end was used for (on the right in this picture)? Is it for the pin used for transit/assembly removed before sale as mentioned?



Thanks

Andrew

[PeterCrespin]

Pete not sure you are correct when you say it was locked down with a pin for transit purposes. I think it was for assembly of the car. I believe they were assembled with the pin in place then it would have been removed. (How much more banging about would the mount have in transit than it wouldn't get during normal road use?).

Sounds reasonable Angus. I was going by what seemed to be the consensus on J-L the last time it came up but am probably mistaken.

As for banging about in transit, I was talking to Brin the other day about an FHC that arrived with a badly dented roof due to being shipped tooo close to the top of a container to allow for full suspension extension or some such. But yes on reflection I may well have been putting 2 and 2 together and making 5. Thanks for the correction. Those 2+2s are not my forte :-)

Pete

[PeterCrespin]

I can see what you mean. Certainly I agree that the box has to be allowed to move up and down and that the nut would prevent this. So if the nut is omitted then the washer must also be too, meaning the centre pin is left free in the middle of the inch and a half hole of the support plate (although fitting snugly in the middle of the centre rubber block). I really need to see a mount in situe to see what it should look like. Like I say, I didn't see it during the strip-down, so I don't know what it should be like. I have access to a V12 (if I can jack it up) would that be roughly the same?

In the original centre pin, what was it that the hole at the bottom end was used for (on the right in this picture)? Is it for the pin used for transit/assembly removed before sale as mentioned?

I think Angus has the right idea and it must have been for assembly but yes, once in service the gearbox is free to float since it cannot go too far down because the mount plate and spring would eventually provide a solid barrier even if the stabiliser didn't. It can't go too high as it is retrained by the stabiliser and ultimately the tunnel. It is free to move fractionally side to side and fore and aft but only to the extent the close-fitting OEM rubber central bobbin allows the pin to compress it a fraction. The resting position leaves the propshaft correctly lined up for normal runnning.

Pete

[PeterCrespin]

The bobbin is shown here...

eBay item number: 110579202083

Pete

[skiday]

I think I now have an understanding of what this is all about. Thanks to your kind replies, and having been able to look at the support of a V12 (which has a nut, but fixed lower down the shaft allowing the box to move);



The bobbin looks smaller than I thought it might be (thanks for finding a pic Peter). When it arrives I should be able to work out a perfect solution, using the threaded shaft, but sleeveing it, and adding a large washer lower down and a locking nut either side to keep it in place, just like the V12 one.

Thanks again, now, on to the next problem???.

[PeterCrespin]

The V12 system uses not just a nut but additional rubber and washer to act as an upward restraint (no rear stabiliser on those engines). As angus said, you're re-engineering this whole system because of the non-standard combination of parts. In fact I am now wondering about the rear engine stabiliser because your LT77 bell housing has no mounting for one does it? The XJ6 which was the only Jag to use that box never had one.

If not, you may have to go the V12 route...

[skiday]

I went to considerable trouble to ensure the there would be a rear engine stabiliser;