Gearbox Part 1 - Now for a Live Transmission from our on the spot reporter....

For those of you who have been following this blog, you will recall that my original intention was to use an LS3 engine with a Tremec TKO600 gearbox.  The TKO600 is a 5 speed transmission capable of handling up to 600 lb-ft of torque.

So despite my change of plans on the engine front, with my Kyle Rushall-built LS7 chucking out a whopping 603 lb-ft of torque, the TKO600 unit should still have sufficient capacity (let's face it, the tyres will probably lose traction before the gearbox implodes....).  There was just one small problem....

Having left my decision to order the said transmission from Roadcraft UK to late Spring 2020, the ongoing COVID pandemic was resulting in a shortage of deliveries from the US of A.  There were no TKO600s to buy!

Plan A - Tremec TKO600 5-speed Transmission (Photo courtesy of Tremec)

Then in Autumn 2020 Tremec made the decision to stop making the TKO gearboxes, replacing them with its new 5-speed TKX transmission.  This is basically an improved TKO, with improved durability for high RPM shifts, still with a torque capacity of 600 lb-ft, but intended as an aftermarket replacement transmission that can be fitted without significant modification to chassis / floorpans.  Small problem though, still no deliveries from the States and Brian at Roadcraft UK wasn't even sure when deliveries of the new transmission might commence.

Some of the bits that make the TKX improved...but still can't get one! (Photo courtesy of Tremec)

Brian contacted me in March 2021 and said that he had a consignment of Tremec T56 Magnum transmissions on the way and due for arrival shortly.  The Magnum is the top of the line of the Tremec aftermarket transmissions.  It is a 6 speed transmission, capable of handling 700 lb-ft of torque, and is essentially an aftermarket version of the TR6060 transmission which is factory fitted to recent cars such as the Dodge Viper, Dodge Challenger and Chevrolet Camaro.  Its basically bulletproof!

T56 Magnum Transmission (Photo courtesy of Tremec)

My only concern with using the Magnum 'box is that it is slightly longer than then TKO gearboxes, which results in a very short prop shaft and, due to the slight misalignment between the output shaft of the gearbox and the input shaft on the rear differential, ends up with the prop shaft being at a significant angle to the line of the gearbox and differential; I was worried that the angle would put undue pressure on the universal joints, especially given the power output of the engine.  

Resulting prop shaft angle due to short distance between diff and end of T56 transmission (photo courtesy of Mark Clayton's build blog)

However, a quick chat with Jon at AK Sportscars reassured me that they install a large number of Magnum boxes in their factory builds and demo cars and do not see the prop alignment as an issue.

So decision made, a deposit was paid to Brian at Roadcraft UK, and I could put my feet up and wait for my gearbox to arrive!