Gearbox leak - Planning for a gearbox and engine pull

[SENC]

As I've been wiping and cleaning things down, I've been planning the various seal replacements. When I replace the sump, there isn't any good reason not to just rotate the engine on its stand and do that replacement upside down, is there?

[mbell]

It's what I did.

[SENC]

Did you find your leak?

Haven't finished cleaning the gearbox or pulled the seal, yet, but peering in it the seal housing is definitely damaged - and I pulled the propshaft and the yoke is clearly grooved, so little doubt the box was leaking from the rear. The forward propshaft u-joint movement is noticeably jerky in one axis, and the rear u-joint stiff in one axis - wouldn't be surprised if they haven't been greased in 50 years. Given the cost of a new yoke and 2 u-joints, I decided to order a replacement propshaft with all the bits from Kelvedon.

grooved propshaft yoke

[2cams70]

That grooving on the yoke surface is severe and abnormal. You will almost certainly need to replace the bush in the gearbox extension housing too.

[SENC]

That grooving on the yoke surface is severe and abnormal. You will almost certainly need to replace the bush in the gearbox extension housing too.

I'd say you're right. Took tailshaft off and bearing damage is also obvious. Looks to me like some debris (maybe part of the dryrotted seal) got in between the bush and the yoke.

gearbox tailshaft bearing

[2cams70]

I'm quite surprised too by the length of the contact pattern on the yoke. I would have expected the Elan with its supposedly rigidly attached final drive unit would have a fairly short contact pattern compared to something with a suspended live rear axle. Maybe check your mountings too? - engine / transmission / final drive.

[SENC]

The transmission mount was pretty bad, and I previously replaced a failed motor mount and not great differential mounts, so could very well have been some movement.

My bigger issue, on further inspection, is that the end of the gearbox extension is cracked, whether a previous problem, damage from pulling it, or damage from my trying to press out the bearing, I do not know. Regardless, I'll need another. I see that TTR/Kelvedon offers some reproductions, but before going to great expense does anyone have a spare? If not, what material would you choose preferentially?

[SENC]

Given findings so far, I've decided the wisest course is a full strip down of the gearbox to id and resolve any other issues. I see a number of resources suggest a special tool for extracting the reverse idler, is that really necessary? Alternate solutions? Any other special needs, tips, or tricks?

[SENC]

Have been pulled away from this project for a bit, but had a few hours yesterday and disassembled my gearbox. In prepping I found some youtube videos someone had posted on putting one together but none on disassembly and several comments that such would be helpful, so while I took some video to share. Not great lighting and awful commentary, but may be useful for someone planning the same in the future or as a cure for insomnia.

Overall, I was pleased with the condition of the shafts, gears, and rings - I was a little worried after my tailshaft bushing findings, but the box and parts were pretty clean so selector forks are the only internals I plan to replace.

As always, open to observations and suggestions.

https://www.youtube.com/watch?v=BHcXB_9y464

https://www.youtube.com/watch?v=DC3WL2GGVK8

https://www.youtube.com/watch?v=Hcgo3ufR4as

https://www.youtube.com/watch?v=Up7KMHMarZU

[SENC]

Main and lay shafts reassembled and reinstalled in the box. If I can carve out some time this afternoon I hope to get the extension on and selector rods and forks reinstalled.

A couple reassembly videos in hopes of helping someone downstream:

https://www.youtube.com/watch?v=0hUcB-4b9C0

https://www.youtube.com/watch?v=rlYP4NCYgys

[SENC]

Installing new sump pan and crankshaft pulley tomorrow - any tips, tricks or advice?

[2cams70]

Be careful where you source the crankshaft pulley. The offset is very slightly different on the Twin Cam compared to the regular crossflow pulley and some suppliers aren't aware of it. Can be corrected for though. Refer my posting about Burton cartridge water pump fitment issues. I take it you will be installing a new pulley seal whilst at it too.

[SENC]

Be careful where you source the crankshaft pulley. The offset is very slightly different on the Twin Cam compared to the regular crossflow pulley and some suppliers aren't aware of it. Can be corrected for though. Refer my posting about Burton cartridge water pump fitment issues. I take it you will be installing a new pulley seal whilst at it too.

Good call on the pulley, I believe I have the xflow rather than the tc pulley - any definite sources for the right one? In the meantime, I'll review the burton thread.

[2cams70]

The QED ones have the correct offset.

[SENC]

Thanks. New problem.

Got my gearbox put back together, all good until I tried to test fit the new yoke into the tail shaft. Starts fine on the splines, but a super tight fit into the bearing (tight enough it would require pressing in). I seem to recall a recent post with a similar problem and the poster concluding the new bearing was undersized, but can't find that post.

Looks like I'll need to pull the tailshaft extension and replace again - has anyone else done this recently that can confirm a source of a properly sized bearing?