Lotus Elan

Gearbox leak - Planning for a gearbox and engine pull

PostPost by: SENC » Sun Mar 31, 2019 11:20 pm

After this winter's layup and focus on carbs and dizzy, I've developed a growing gearbox leak. I had a known angle drive leak and was hopeful that was most of my problem, but after resolving it still have a healthy leak. I'm suspecting a rear seal or yoke problem - anything else I should prep or look for?

I've started reading and making notes for an engine and gearbox pull, and though I try to avoid too much "while I'm there" work, I'd like to avoid pulling them twice. My engine is leaking around the sump and I have a baffled replacement sump on the shelf so solving that problem while out is a definite. What else should I do as a matter of routine maintenance reppacement while I have them out?

As always, any and all suggestions or guidance is welcomed.
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PostPost by: rgh0 » Mon Apr 01, 2019 12:41 pm

Rear crank seal, clutch overhaul, clutch throw-out bearing replacement, gear box front seal replacement I would all do depending on mileage since last done, If pulling the engine and gear box to do the tail shaft bearing and seal.

And of course the sump if you have a new baffled one to go in. I would also replace the engine front crank seal depending on mileage but that can be done without removing the engine if needed ( just the radiator) so not so critical.

Anything else in the engine bay that's easier with the engine out I would do also

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PostPost by: joe7 » Mon Apr 01, 2019 1:40 pm

Make sure the threads in the rear of gearbox for the bolts that hold the exhaust bracket aren't stripped. I've seen a few.
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PostPost by: SENC » Wed Apr 03, 2019 5:32 pm

Thanks Rohan and Joe. I've noticed that the bolts along the frontside of the sump are missing, so have a suspicion those threads may be stripped but assume I can fix with helicoils, correct?

Will check with prior owner on last clutch rebuild as well as memory on the sump bolts, but suspect I may as well do the clutch throwout bearing at least.

I've also noted that the crankshaft pulley is missing a few bits along the inner rim as if at some point it made contact with the sump/block connection, though no signs of anything ongoing or in recent history so may have been this way for a ling time. Will inspect more closely when I get the engine out, but will definitely replace the pulley.

I have an original chassis with integrated crossmember - is the recommendation still to remove it and replace with a bolt-on version to make future sump replacements possible in situ?
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PostPost by: AussieJohn » Wed Apr 03, 2019 7:19 pm

New clutch bearings seem to be suspect, the chamfer on the back of the bearings are too big so the bearing only sits on a tiny bit of the carrier. Worth checking that the bolt which acts as a gearbox breather is not blocked.
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PostPost by: gjz30075 » Thu Apr 04, 2019 9:22 am

SENC wrote:I have an original chassis with integrated crossmember - is the recommendation still to remove it and replace with a bolt-on version to make future sump replacements possible in situ?


I removed the crossmember in my original chassis, not so much for in situ sump work but for much easier
work for R & R'ing the headers when pulling the engine.
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PostPost by: 69S4 » Thu Apr 04, 2019 9:48 am

Having just spent most of yesterday morning wrestling the manifolds out of the car I'm going to 'convert' the cross member to bolt on while I have the space - probably over the next day or two. Unless there's a good reason not to. Arguments one way or the other taken into consideration before the cutting disc gets a workout.

Suggestions as to how the bolt on ends to the cross member should be fabricated also welcome. I've gone back though old posts on the subject and it looks like there's a few different approaches.
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PostPost by: rgh0 » Thu Apr 04, 2019 10:01 am

One of the best mods I ever did back in the 70's soon after i got the car and i carried it through to the new chassis i fitted in 1980. You have probably seen photos of how I did it if you have researched posts. Note that the gap widens when the brace is removed when you to build it with the weight of the car body and engine on the chassis. You need to bring the gap between the chassis arms to what it was before you removed it when drilling the mountings for the removable brace.

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PostPost by: Craven » Thu Apr 04, 2019 10:30 am

Before removing any sort of bracing member/bar drill small pilot reference holes through both parts.
This will provide after removal the exact spacing between the parts and a pattern for the new brace.
I used this simple procedure when making a new bottom plate in a door frame where there seemed to be a good chance of the upper frame springing apart.
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PostPost by: snowyelan » Thu Apr 04, 2019 6:52 pm

I used Yum-Yums method that he outlines at the bottom of his description, no alignment issues to worry about.

viewtopic.php?f=31&t=23126&start=
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PostPost by: 69S4 » Fri Apr 05, 2019 9:10 am

The Yum-Yum method, or something like it, is more or less what I had in mind to do but I'm having trouble finding channel section steel of suitable dimensions so it may be a modified Rohan.

What caught my eye though was Rohan's remark 'the gap widens when the brace is removed ... with the weight of the car body and engine on the chassis'. At the moment the engine is mostly supported on blocks with one of the mounts removed so I guess there isn't too much spreading pressure. Cutting the brace and constructing a new one shouldn't cause too much of an issue. However if, at some point in the (near) future, I then want to make use of the removable ability to take the sump off (it's an oily mess under there) am I going to have problems with the chassis spreading. Or am I overthinking this?
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PostPost by: rgh0 » Fri Apr 05, 2019 9:24 am

HI Stuart

The spread is small - less than a millimetre on my chassis as you are not far from where the body bolts to the chassis at this point . A chassis with no body fitted may spread more depending on residual stresses in the chassis and what else is fitted. With fitted size holes in the chassis the bolts did not slip in with this small spread. I machined a slight taper on the first couple of threads and then the bolts can be screwed in the fitted holes and pull the chassis back to the alignment as you do that and the nuts are then tightened on the bolts. i use a large flat washer on the top of the chassis flange as well as the plate the channel is brazed to on the bottom.

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PostPost by: SENC » Sun Apr 21, 2019 1:30 am

Got through the bulk of strip down in prep for pulling the engine and transmission, with 2 final hurdles perhaos some of you can advise on:

1 - the 2 bolts that hold the rubber mount to the gearbox bracket. I can get to the nuts from the bottom of the bracket, but they just spin the whole bolt. I can't feel the bolt-heads on the top to try to figure out how to hold them with a wrench - presumably a combination of oil, rubber, and road grime. I'm thinking the best bet is to drop the gearbox bracket from the subframe and try to get at the mount after I get the tranny out. Any better ideas?
2 - the plastic cap/dome that screws into the gearchange turret is stuck, and I can't see any good way to get at it. It needs to come out so I can remove the lower section of the gearchange lever to get the box out. Any tips or suggestions?
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PostPost by: 69S4 » Sun Apr 21, 2019 7:40 am

I’ve just had those brackets apart on my S4 and the two bolts you mentioned are awkward. Mine were the other way round with the heads downwards and the nuts ‘inside’ the rubber mount but unless the heads are damaged I don’t think it makes much difference. I did eventually find a short ring spanner with a deep offset that would fit in there - the same one I use for the Stromberg mounting nuts. There is space in there to get on the bolt heads but you do need double jointed fingers.
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PostPost by: gjz30075 » Sun Apr 21, 2019 9:16 am

Yes, not easy. I tack welded the nuts on the topside.
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