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Oil leak Gearbox/Overdrive/Speedo Angle Drive take-off


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I have been under my car this weekend checking out two problems:-

1)      An oil leak on my 1974 TR6.

2)      Odometer working intermittently, whereas the speedo continues to work normally.

1) The oil leak

My initial investigations showed the oil to be coming from somewhere around the J-type Overdrive, possibly the angle drive for the speedo takeoff. I believe the angle drive may be part of the cause of the oil leak. The Angle drive appears to have a relatively large amount of movement on the joint below the collar which screws into the overdrive, which I would not expect.

Is this a possible leak source? And is any amount of movement on this collar joint normal?

Further investigations today from below suggest the oil may be coming from topcover above the overdrive.  Further investigations are ongoing, think I need to take the tunnel off to check from topsides today.

2) Odometer working intermittently

I have noted that the odometer had been stuck on 43999 for some while, but finally tripped over recently after being stuck for 20 odd miles,  whereas the speedo appears to be working fine.

In my oil leak investigation,  I have found the outer casing of the speedo cable has been melted in one location by the exhaust, having not been supported in one location.  I wonder if this may have had some internal impact to the cable, and be a contributary cause for odometer not working correctly?  Or is the speedo head the problem here?

Any thoughts/comments gratefully appreciated.

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The odometer fault is in the speedo itself Josh. There is a gear that wears or breaks and a pawl/ratchet that can cease to work properly. With luck since yours works now and then, it may just be that the rotors have become too sticky to move easily. 

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Josh,

To confirm the leaking  area clean the gbox & overdrive and dust with talcum powder, leaks will show up with trails in the oil. Then you know where to start.

Also locate the breather hole in the gbox ( not easy find) and check that it is clear it, is very small and easily blocks.

Alan

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2 hours ago, Josh said:

I have been under my car this weekend checking out two problems:-

1)      An oil leak on my 1974 TR6.

2)      Odometer working intermittently, whereas the speedo continues to work normally.

1) The oil leak

 

Further investigations today from below suggest the oil may be coming from topcover above the overdrive.  Further investigations are ongoing, think I need to take the tunnel off to check from topsides today.

 

Any thoughts/comments gratefully appreciated.

Hi Josh,

there has been quite a flurry of experiment and R&D on the seals for the selector rods.

The originals are simple 'O' rings and tend to leak.

I've tried 'Q' seals and they also leaked - from that I would suggest that the counterbore where the rings fit are worn.

It is possible to fit 3/4 x  1/2 lip seals.  I have great faith in this but not tried it on a working GB yet.

Read this thread  

 

 

The angle drive should not be loose. Pray that the PO has not cross threaded the nut.

 

Roger

 

Edited by RogerH
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Roger,

Many thanks for your suggestions.  Unfortunately I didn't get to it as planned, but hope to have another crack this weekend. 

In the meantime, having not opened up the top cover,  you mention 'O' rings may be the problem, when I get inside, which I will certainly check.

Also, could you enlarge on fitting of 3/4 x 1/2 lip seals - Where do these fit, and where can I source these if needed?

Thanks again

Josh

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Hi Josh,

firstly sorting out the 'O' rings is not straight forward but easy enough if you are adventurous.:blink:

See here for the 'O' rings  Item 100  3 off  'O' rings

You need to remove the selector rods so as to get at the 'O' ring counter bore.  This is not complicated but MUST be done is a particular sequence. Ask if you need to know.

If you go down the 3/4" lip seal route you will need to either obtain a special milling cutter with 1/2" pilot of we can sort something out  - where do you live.

The lip seals can be obtained from most Bearing/Seal suppliers - I used Brammer. Part Number     NBR07505013A

 

Roger

Edited by RogerH
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If you use o rings you need to make sure that they are locked by the plate, I think the ones supplied now are just that bit too small, if the ring moves it will pump oil out, I have fitted quad rings with backup rings to minimise the movement as the quad rings are a bit smaller in thickness, mine are still holding good.

John

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  • 5 weeks later...
On 7/2/2020 at 1:51 PM, RogerH said:

Hi Josh,

firstly sorting out the 'O' rings is not straight forward but easy enough if you are adventurous.:blink:

See here for the 'O' rings  Item 100  3 off  'O' rings

You need to remove the selector rods so as to get at the 'O' ring counter bore.  This is not complicated but MUST be done is a particular sequence. Ask if you need to know.

If you go down the 3/4" lip seal route you will need to either obtain a special milling cutter with 1/2" pilot of we can sort something out  - where do you live.

The lip seals can be obtained from most Bearing/Seal suppliers - I used Brammer. Part Number     NBR07505013A

 

Roger

Roger,

Many thanks, and many apologies for my belated reply, I have been tied up recently on a range of unexpected family business, so this has had to take a backseat.

Anyway, today I have finally got round to taking the tunnel off the gearbox, to find that I do indeed have a significant amount of oil being supplied from the selector rods (see picture) which would suggest that I have selector rod seal problems.

You mentioned that dismantling needs to be done in a specific sequence - I assume this the detail you shared on another thread with Z320 (Marco from Stuttgart) with details from Buckeye website?

Also, I'm thinking I'd like to pursue the 3/4"  lip seal route provided that is a more robust/long term solution than just replacing existing seals. 

Or is it possible to  combine the two solutions in one?

Do you have any sense of how long I should expect normal seals to last and how to go about installing?

I am based in Gerrards Cross,  Buckinghamshire,  so not a long way from West London.

I'd be interested in your thoughts

Thanks

Josh

 

 

 

DSC_1471.JPG

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Josh,

the seals in your GB are probably 50 years old and probably died quite a while ago.

If the rods are not badly weathered where they meet the 'O' rings then any decent seal would probably give a result. however I would stay clear of O rings.

The 3/4" lip seals need the O ring counterbore opening up. I have a special reamer for this (3/4" OD cutter _ 1/2" Pilot)

If you do not want to attack the rod removal  I would be happy to do this for you and put the seals in. The rods can be inspected at the same time.

The only problem with rod removal is that always one or more of the wedgelok screws break off. Getting the remnants out can be fun !!!

 

Roger

 

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Roger,

Many thanks for your kind offer of assistance, which I'd be delighted to take up, given that I am still a TR novice only having had my TR6 for a couple of years, and I'm finding problems that built up over time and were not addressed by PO.

Ordinarily I would like to work alongside you and learn from those of you who are much more experienced on the forum, but unfortunately, I am shielding a family member with COVID.  But I would still be very happy to order the lip seals and I could drop the top cover assembly round to you for your machining expertise if that would be ok?

If you could let me know how best to proceed, I'd really appreciate it.

I've attached another picture of the rods having done an initial clean up of the selector box now I have separated it from the gearbox

Many thanks

Josh.

DSC_1486.JPG

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Hi Josh,

they look a bit weathered but it must be worth a try.  

If you want perfection then you would need to get the rods cleaned , pickled, Chrome plated, and ground to size.  This could be done in the future if need be

 

Roger

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