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Engine to Gearbox alignment


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Hi Folks

I was planning to temporary fit the engine and box to the car to check all the panel gaps remain the same with some weight through the chassis before I send the shell for blasting/paint.

I've just been reading the post regarding gearbox noise and Roger made reference to "alignment bolts" I was expecting there to be the normal dowels on the box or engine block but there are none so I guess its important these bolts are in the correct position. Unfortunately I've none of the original fitting hardware or reference pics as to where each of bolts (or studs fit which I gather are the top three holes) and more specifically where the two alignment bolts fit in exactly in which holes in the bell housing bolt pattern. The Moss and Rimmers schematics aren't clear and the TR6 Brown repair manual makes no reference to the alignment bolts. nothing on much google images. 

Don't suppose anyone has any more specific diagrams or sources or tips getting the alignment right?

Thanks Andy 

 

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Hi Andy, if your doing a temp fit then I wouldn’t worry to much. The position of the two dowels are around 2ish and 7 ish o’clock .these are slightly larger diameter than the rest of the holes. Apart from starter motor bolt holes.

If bolts replace dowels they should have a shank that penetrates both engine plate and gearbox bellhousing.

hope this helps.

Mark.

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As Mark says for temp fitting it will not matter, BUT for permanent installation, two 3/8 shouldered bolts

fitted at 2 O'Clock and 8 O'Clock, as looking at the engine from inside the car,  are critical to the gearbox alignment on a 6.

I have had over the years, at least,  three different cars, that all had clutches replaced in

an ordinary garage, "Sure guv' straight forward that, " That did not know, and consequently did not correctly replace these bolts.

Result is a hobbible operating, on/off clutch with little or no progression that makes driving the car a nightmare.

There is nothing special about the bolts, other than that they are 3/8 UNF with about a 1 inch shoulder.

John.

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Thanks Mark, John, CK and Harald perfect info as ever! Bolts ordered. 

Don't you just love this forum.:D

Thanks again

Andy

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On 1/5/2020 at 10:04 AM, PodOne said:

Thanks Mark, John, CK and Harald perfect info as ever! Bolts ordered. 

Don't you just love this forum.:D

Thanks again

Andy

Just remember to fit the dowel bolts first before tightening anything else.   They should be a push fit.

Or you will discover the close tolerance holes in engine back plate and gearbox flange don't line up......

Peter W

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  • 2 years later...

Hi all,

Just received two shoulder bolts as mine were missing. I think the shank on these is too short, from the comments above the shoulder should extend through the gearbox housing and engine plate. Can anyone confirm?IMG-0115.thumb.jpg.09e4c2e0bb72b0bc6ed4df5256d5180d.jpg

Thanks Tim

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Thanks John,

Just measured the depth and the shoulder should be in region of 20mm.

First time working on the gearbox. The parts diagram indicate that the heads of the bolt are engine side, and no washer on the engine side. Locking washer and nut on the gearbox side. Is this correct, or should there also be a washer on the engine side too?

Thanks

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I agree, the shank should fill both holes (af least most of it), but not extend.

Waldi

Edited by Waldi
Typo
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On aluminium surfaces it is good practice to have a flat ring first to prevent damage by the hex head to the aluminium. It does not hurt having flat rings both sides, however.

Waldi

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Not sure if there is a preferred way Timo, but I have always followed the Moss catalog, even if I thought it did not matter (because sometimes it does, like with the trailing arm mounts).

Cheers,
Waldi

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  • 2 weeks later...

Thanks Waldi, Harry,

After a second failed attempt at getting bolts with a suitable length shoulder from one our main suppliers, I sourced some with a 15mm shoulder elsewhere. Up shot off it all is that I now have a super smooth clutch! Such a relief I didn't have to remove the gearbox.

Feeding back on my experience it was evidently easier to insert the alignment bolts from the engine side. In fact for one of the holes on the gearbox it appeared that it had not been drilled through all the way and could not even insert from the gear box side. Also with inserting from the engine side ensured the shoulder engaged well with both the engine plate and gearbox as the engine plate is the thinner than the gearbox casing.

regards Tim

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