This blog is intended to document the build of my Gardner Douglas Mk4 Cobra; partly as IVA evidence, bit primarily to help others learn from my mistakes and/or successes.

I will endeavour to post as often as possible, with a view to entering a single post for a particular element of the build process, however inevitably some things may not be completed in one go. All posts will be tagged so it should be easy enough to find the information you seek.

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Tuesday, 2 February 2016

Gear Box Options

So the final decision of Orange with Carbon Fibre stripes has been made and the body is in the mould as I type.  I was hoping to pick it up this weekend, however one thing or another has delayed proceedings slightly, not to worry as there's still loads of prep and research to do.

Another decision I have already made is that I will be using an LS3 but as an engine and gearbox combination from new will set me back around £12k I've been exploring the possibility of a second hand unit.

LS3s are used in a myriad of American Muscle cars and a fairly readily available in the US, but after paying a minimum of $9k + shipping + import duty + VAT it's not that viable so I've ruled that out.  As far as I know the only UK sold car to come with an LS3 is the Vauxhall VXR8 which aren't exactly ten a penny, so finding a pullout is tricky, but I think I've succeeded.

There's a guy called Gary who runs a site called www.LSXV8.co.uk and is about the only UK breaker of Monaro's and VXR8s.  I got in touch and was surprised to hear that he had a low mileage (28k) 2009 LS3 with 6 speed manual available which has everything except ECU and loom, lovely.

Whilst I wait for him to put it back in a car so I can see/hear it run my thoughts turn to the gearbox and it's many guises.  He tells me it's a T56, however there seems to be about a million different variants with a million more gear ratio combinations and shifter locations, so I delve deeper....

After many hours/days of trawling Google and various forums, I 'think' it is either a TUET-2066 (T56), TEUT-2100 (T56) or TUET-10310 (TR6060) but am still waiting  back from Gary to confirm the correct part number.  In the meantime I have created a spreadsheet to compare the above three options and the T56 Magnum which GD use.

Tremec Transmission Comparison - Cruising

One of my considerations is the usability of 6th gear for cruising so you can see the relative RPMs at 80 MPH (not that I would actually drive that fast on UK roads!)  All are under 200 RPM so will offer reasonable full economy on long journeys.
Tremec Transmission Comparison - Speed
This time I've left the RPM the same so you can compare the speeds in each gear, the TUET2100 is my least favourite as I think 6th would almost become redundant so that is out.  The TUET2066 is a better set of ratios but reliability has been questions in the VXR8 community which is why Vauxhall ended up replacing a lot of them with TR6060s under warranty.

The TUET10310 is said to be much more reliable a less agricultural than the standard T56 so this would be my preference if it turns out that is what is currently attached to the engine, however both the T56 and TR6060 in a VXR8 would have a remote shifter so this would need to be repositioned.  Worst case I may end up having to get just the engine and sourcing a new T56 Magnum.

The spreadsheet automatically calculates everything by changing the ratios, RPMs or wheel and tyre sizes.  If anybody out there wants a copy let me know.

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