T5 Gearbox S10 Tail Housing conversion

Before I begin I must mention David Byron to thank him for his assistance and guidance with this modification.

All TVRs from late Griffith onwards use the Borg Warner T5 gearbox. Griffith and Chimaera used an earlier tail housing for the T5 box which required an additional linkage to bring the shifter out in the correct place.

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On the later ‘T’ cars TVR used the S10 tail housing which presented the shifter in the correct place and did away with the additional linkage.

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The basis of this modification is to retrospectivily fit the later S10 tail housing to the T5 gearbox in my Griffith, thus deleting the additional TVR linkage and improving the feel of the gearbox. I also opted to complete a number of other small enhancements along the way.

John Reid at Readman Racing (Grantura Engineering) has been offering this upgrade for a while and supplies reconditioned S10 tail housings with a new top section with all new bushes and the new selector etc so that the two complete units can just be swapped straight over. From speaking to other owners who have completed the modification a new mount for the gearbox is required and also the TVR remote linkage offsets the gear lever by about 2 inches toward the driver so a dog leg needs to be introduced into the shifter to present it in the same position as before.

As part of the S10 package I also purchased a bronze shift cup and bronze shift forks to replace the standard plastic items again supplied by John Reid.

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I also opted for a replacement Hurst shifter with improved pre-loading to make shifting from 2nd to 3rd easier. I purchased a custom Hurst shifter from Core Shifters built specifically for S10 T5 boxes and with a custom fulcrum height designed for the 6 inch TVR stick.

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Finally I decided upon a custom Stainless Steel gear knob from Chris at Lathewerks in the USA. Machined from a solid block of steel and weighing in at 550G it is approximately 3 times heavier than the original TVR item and has a slightly bigger circumference.

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David Batty my TVR specialist has completed the modifications to the gearbox while changing the clutch and replacing the leaking rear main oil seal.

First impressions are good, it is now easier to select gears at the far end of the box (5th and reverse). The Hurst shifter has reduced the distance between the gears slightly and has a more positive self centering effect. I will update this once I have done over 1000 miles to get a feel for it.

1000 mile update – I have since completed a RWYB day at Santa Pod, a number of long 300+ journeys and a track day at the Lotus test track. I am pleased with the improvements to the gearbox and definitely worthwhile if the box is coming out anyway, I would personally not recommended spending the money on labour removing the box just to have this mod done. The difference is not night and day different just subtly improved.

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