Lotus Elan

Gearbox Question Re Interlocking Plungers

PostPost by: ceejay » Tue Apr 10, 2012 9:21 am

Hi all.
While doing a top end gearbox check and minor rebuild of the gates and selector rods,
the interlocking plungers were displaced, they ended up in the bottom of the box
which has been drained and thoroughly flushed out, so it wasn't a problem to recover
the plungers with the G/box mounted on the engine stand.

While looking at the exploded diagram in the W/shop manual I can see what looks
like three interlockers. Which makes me think that one is missing and has perhaps
never been in the box which has been in service for 27 years as is.

Hence the question re the number of interlocking plungers?
Any body know how many there should be?
Ceejay.
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PostPost by: garyeanderson » Tue Apr 10, 2012 10:33 am

Hi CeeJay

These are what come with every Ford box in an Elan there is also two other shift rails and 3 jam bolts for the 3 shift forks

Elan gearbox interlock and detents.JPG and


Elan gearbox interlock closeup.JPG and


Elan gearbox.JPG and
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PostPost by: ceejay » Tue Apr 10, 2012 10:50 am

OK, thanks, no dramas with the springs and ball bearings...all Ok there.

The problem was with the interlockers, and it looks like there are only
two... so that's OK, but I do not have the smaller diameter pin that
appears to pass through the hole in one of the the shift rods.

I have a spare standard ford escort gearbox. so might "borrow"
some parts from that tomorrow to complete the rebuild.
Strange that small bits and pieces can be omitted in
a gearbox, yet it has been a gem of a box for decades.
Thanks for your input.
Ceejay
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PostPost by: garyeanderson » Tue Apr 10, 2012 11:11 am

Check in with the needle bearings. There are 20 on each end of the countershaft (second motion) and one more that Ford used to hold the Reverse select dangler in place. They are not the same size or shape but they all fall into the bottom of the box (you need to rotate the center shaft 90 degrees) when you extract the shaft for the shift lever engagement area when you dis-assemble (except for the reverse dangler retainer pin). The part number for the pin (gear change shaft interlock) is 105e - 7235. Probably only one per car, if not certainly only one per gearbox. If you want a length I can find one and measure if you want to make one.

Gary
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Elan gearbox interlock and detents diagram.JPG and
Last edited by Guest on Tue Apr 10, 2012 11:17 am, edited 1 time in total.
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PostPost by: ceejay » Tue Apr 10, 2012 11:16 am

Thanks again.
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PostPost by: garyeanderson » Tue Apr 10, 2012 11:38 am

Ceejay

I measured two one was .425 inch and the other was .422 inch and the ends are sightly rounded. Diameter is .140 inch

Elan gearbox interlock pin length 425 thousants.JPG and


Elan gearbox interlock pin length 425 thousants1.JPG and


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PostPost by: Tonyw » Tue Apr 10, 2012 2:10 pm

Ceejay,

I have a trashed box so if you are stuck PM me and I will post the offending bit to you (assuming I can find it)

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PostPost by: garyeanderson » Tue Apr 10, 2012 5:07 pm

Tonyw wrote:
The complete information source for Lotus Elan sportscars.



Hi Tony
That's a much better offer than what I could do, I hope you can find the part...

Gary
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PostPost by: ceejay » Tue Apr 10, 2012 8:52 pm

Thanks guys, I think I will be OK now, everything else is ok with the box,
it was just the qty of interlockers... the small pin has never been in the box
but operated as per normal.
Thanks for the offer Tony.
Ceejay
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PostPost by: Elan45 » Wed Apr 11, 2012 1:37 pm

I'm afraid I couldn't sleep at night knowing there is a possibility that that pin is still in the bottom of the gearbox. It is loose things like this that wreck perfectly good gearboxes. Try a magnet on a stick or even remove all the gears from the box to find it. I just went through a similar experience when completely rebuilding my box last year. I knew it was there but lost it after starting reassembly. I finally found it on my brick driveway where I had dried the parts after washing. I suppose it may have been left out during a rebuild, but I'd have to know for sure.

Roger
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PostPost by: ceejay » Thu Apr 12, 2012 10:32 am

To ease my fears and yours Roger, while the gearbox was still mounted on the engine
stand I drained all of the fresh 90 gear oil out and poked and prodded with a bit
of thin wire while tilting the box through some steep angles, and also blew high pressure
air down through the shift rails and gears... the result... nothing, no stray pin.

It was never in the gearbox, that is why I asked the question in the first place
about the plungers, I had two fat interlockers... but no thin pin, and was very
careful when I pulled the shift rods out. The missing pin was probably the
reason why on very odd occasions in the past when changing from third to second,
reverse was nicked with the resulting brief gear screeching sound.... yuk!

BTW, the stand that the gearbox is mounted on is a multi purpose stand,
I have made attachments to hold the engine, gearbox, cylinder head,
and the Diff for rebuilding etc, plus another special bracket to hold and
work on a brass radiator, but I don't need that now as I have a nice
PWR Alloy cross flow.
The gearbox mounting tube has a special threaded adapter
welded to the tube which is screwed into the gearbox filler hole,
and pulled up firm with a cross bar.
Ceejay.
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multi-purpose-stand-0007.jpg and
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PostPost by: rgh0 » Fri Apr 13, 2012 11:11 am

Hi Col
with the centre pin missing the interlock function that prevents selection of more thyan one gear would not have worked. Its a compliment to your driving and gear change precision that you only had the occasional crunch when you happened to pick up two gear at once

cheers
Rohan
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PostPost by: ceejay » Fri Apr 13, 2012 11:26 am

Well thank you Rohan, it bugged me for awhile, but it is only just
occurred to me why it used to happen, I must admit I was a but
timid at times when coming back through the gears.

Maybe the neat gear selection was because as a youth (15-16 year
old) I perfected changing gears in 1949 KM series Bedford farm truck
fitted with a four speed crash box.... and believe me, if you got it wrong,
there was an almighty gear crashing sound.... this old thing also
helped me to perfect the double de clutch action.... like riding
a bike, once learnt, never forgotten.

I reckon the elan gear box is the sweetest thing for cog swapping,
there ain't many gear boxes like it.
Col
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PostPost by: rgh0 » Fri Apr 13, 2012 11:33 am

Yeah I agree
Coming onto the sweeper into the main straight at Phillip Island you change up from second to third to to fourth while holding the car on the limit and accelerating hard on the limit of inside rear traction and outer front tyre steering grip. It really helps to have such a sweet box where you can shift quickley and surely with minimum effort while concentrating on keeping the car on the track.

It why the Elan is such a joy to really drive hard :D :D :D :D :D :D :D :D

cheers
Rohan
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PostPost by: ceejay » Fri Apr 13, 2012 11:38 am

I have never driven on PI track, would love to experience it one day,
I better put it on the bucket list
Col
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