Transmission parts

5th gear conversion for all 4-Cyl Esprits 1987-1999:

- Ratio 0.75 : 1 instead of the stock 0.82 : 1
- Reduce rpm /cabin noise when cruising (around 500rpm at speed) or....
- .....increase top speed with a tuned-up engine !!
- Max. possible speed rises from 173mph @ 7500rpm to a phenomenal 192mph @ 7500rpm !!!
- Very high quality hardened gears
- Easy installation: just remove the rear housing, G/B itself stays insitu !

LSD Limited Slip Differential, ATB-type, suited for ALL Lotus Esprits with Renault Gearbox (MY1988-2004)

- Automatic Torque Biasing (=ATB) patented design - Controlled power transmitted to both driving wheels - Automatic proportional operation, progressive curve but never locks ! - Eliminates harsh torque steer characteristics of other LSD - Completely gear operated design, NO plates - Works perfectly in all traction conditions - Direct fit ! Fits perfectly in your Esprit-Gearbox ! No modifications needed.




Technical principle:

Sets of floating helical gear pinions mesh to provide the normal speed differential action. In the event of one wheel slip, torque bias is generated by the axial and radial thrusts of the pinions in the pockets. Re resultant friction force enables the driving road wheel and sun gear to transmit a greater proportion of the torque. This effect is progressive but at no stage does the differential lock solid !

PUK uprated complete Esprit Gearbox upgrade Kit, for all Esprits with Renault Transmission (MY1988-2004)

Like you all know the Renault UN1 gearbox that is used in our beloved Esprits since MY1988 is not the strongest one on this planet. On the other hand its a very very well engineered device, yet not heavy (just around 50kg without bellhousing !!!!) that is perfectly suited to fit in a mid-engined car like the Esprit. The achilles heel when used with high power are mainly the weak primary shaft and the overhung 5th gear.

Problems in detail:
1) the overhung 5th gear (like many 5 speed boxes, the 5 speed UN1 is the earlier 4 speed version with an extra gear hung on the end!). This 5th gear likes to break (overhang shaft flexes and breaks) in the V8 Esprits quite regularly. This usually happens in 5th gear at around 5000-6500rpm when you lift the throttle for a second and initially put your foot fully down again. No fun ... ;o/
2) the small diameter splined link between the clutch/input shaft, and the first motion shaft
3) Flexing of the first motion shaft between the two ball bearings due to the thrust pushing them apart
4) second gear and second gear synchro rings

For more details have a look at: Bell Performance

Mr. Derek Bell developed a very good upgrade kit for the UN1 gearbox for his "Ford-Lola-race-car" applications. This upgrade is the basis for our gearbox upgrade. Of course we donot use a FORD-spline on the clutch/input shaft ;o)

As a core you have to use your original Lotus UN1-gearbox that gets upgraded using the following new and upgraded parts ...

- all new bearings
- one piece new "big" primary motion shaft
- new special bearings for the primary motion shaft
- stronger first gears
- stronger second gears






Please note ! Your existing gearbox must be in good running order ! For the upgrade you will need to reuse the complete housing and the final drive (= crownwheel and pinion and differential). At least these parts have to be in very good shape !
 
For ordering please also tell us what Esprit model you own:

UN1-016: 4 Cylinder G/Box - First variant of Lotus UN1- First used on X180 Introduction in 1988. This 'Box had rear cover with L/H shift lever

UN1-026: High Torque G/Box - Stronger Casings etc. introduced circa 1993. This 'Box had rear cover with R/H shift lever

UN1-027: V8 Gearbox - Introduced in 1996 on V8 Esprit. This box was basically similar to 4 Cyl High Torque unit with new Clutch Housing. It carried over the R/H shift lever. It had synchro on Reverse Gear. A higher 5th gear. The shift mechanism was changed to an improved version of the R/H mechanism from VIN W2272 - this requires a different shift master unit and cables

UN1-028: 4 cylinder G/Box for the Esprit GT3 (2.0 Litre) with a different Axle Ratio and Gear Ratios

!!! We offer this upgrade as a kit (including all parts) for DIY installation !!!

If you are planning on both a Limited Slip Differential and a Gearbox Upgrade, then why not order both at the same time ! :o)