New Tremec T5 Gearbox

It has come to light after more detailed measurements that my Borg Warner T5 I've had for some years is not suitable for fitting to the Rover V8 in the Scimitar. as such I have purchased a Tremec T5 with 30K miles on the clock form a TVR Griffith that met its doom with the aid of a lamp post.

The Box from the TVR is manufactured by Transmission Technologies Corporation (TTC) under the Tremec brand after a sale of the gearbox design, however the design and build of the box is identical to the earlier Borg Warner counterpart.

The new TVR box itself is in fact originally a derivative of the gearbox for the Ford Mustang and although the same basic gearbox as the Cosworth gearbox there are some dimensional differences between the two units, the main reason for opting to use the TVR Box over the Sierra Cosworth Box. The input spline is identical to the Cosworth box however the OD of the output shaft is larger and contains 27 splines over the Cosworth 25 splines but this isn't a problem, it just means a TVR slip yoke instead of a Ford slip yoke. The main reason to choose the TVR Box is the position of the gear selector, after a mock fitting it was found with the gear stick position is far too far back from the dashboard to be practical while driving.

 

Despite the differences in dimensions the gear ratios are the same as the Cosworth Borg Warner T5:

•  1st = 2.95:1

•  2nd = 1.94:1

• 3rd = 1.34:1

• 4th = 1:1

• 5th = 0.80:1

The reason for the swap is some years ago I turned down the face of the nose in the Cosworth box and parted off a section of the thrust bearing shaft in order to adept the nose to fit into the new bellhousing and work with the concentric slave cylinder.
It goes without saying I will replace the main taper roller bearing and the mating race pressed into the nose too, as its never clever to swap to races and bearings that have been ran in together.
The new Tremec 5 Speed box with light weight Rover V8 bellhousing and concentric salve cylinder built up and complete ready to be bolted up and fitted into Scimitar to begin getting the engine positioned and a new gearbox mount measured up and fabricated.

The current Scimitar rear axle final drive ratio is 3.31:1

The V8 will have a Peak power at 6000 RPM and an inflated Tyre diameter of 12.126."

Speed in each gear at peak power of 6000 RPM:

• 1st = 44.3 MPH

• 2nd = 67.4 MPH

• 3rd = 97.6 MPH

• 4th = 130.8 MPH

• 5th = 163.5 MPH

The Cosworth box will not go to waste, future plans will see it fitted to another project car. the new box is solid and with only 30k miles on the TVR's clock before it was glass-fibre dust the gearbox will not require a full rebuild like the Cosworth box.

 The Cosworth T5 box bolted to the engine in mock position.

A new hole was cut into the transmission tunnel for the gear stick to protrude, with the seat in situ  its obvious the gear stick is over 5" further back and going to be awkward to operate.

The Tremec Box will position the stick closer to the dashboard, actually approximately 3" closer to the dash than the original Scimitar gearbox.

I originally bought a JED lightweight bellhousing with a concentric type slave cylinder some years ago for the Cosworth box this will now be fitted to the TVR box. to do so I will need to swap the front bearing retainer nose from the Cosworth box to the TVR box and vice versa.

Some years ago I modified the bearing retainer nose on the Cosworth box to fit into the JED bellhousing. I did this by parting off a section of the noise originally the sliding surface of the thrust bearing to allow the gearbox to mate up with the concentric salve cylinder which replaces the thrust bearing. I also turned down and faced off a good 1/4" of the front face of the nose casting to allow it to mate correctly. 

As these two parts are identical swapping them over will be easy just a matter of 8 bolts and knocking out and re fitting the two bearing races.

This will allow me to us the TVR Tremec box without modifying its nose and return the Cosworth Borg Warner box back to stock, ready for the next project.

As I plan to use the Cosworth box with a different application in the future I will simply swap the modified nose for the original one returning the Cosworth box back to original spec.

It goes without saying I will change the taper bearing and race with the noses. as its not very clever to swap a bearing and race that have been ran in together.

The new gearbox assembly ready to assemble into the car for final engine positioning and  to allow for a new mount to be designed and built.