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Esprit GT3 "upgrade"

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  • 1 year later...
On 09/12/2020 at 16:11, plumdeplakmuis said:

V8 makes 400Nm so I guess the GT3 should be able to cope with it. 

GT3 gear box is NOT the same as later V8! I would suggest an upgrade!

All the UN1 Lotus Gearboxes are very similar. This is the 'simplified' history.

These changes included Revised Gearchange & Synchro on Reverse Gear. The introduction of the Esprit GT3 created another variant of the UN1 gearbox. This variant is only approved for the 2 Litre version of the Lotus Turbocharged engine. This version of the UN1 is designated UN1 – 028 and has a different Crownwheel & Pinion that is only suitable for use and validated for the GT3 engine. UN1- 028 is not recommended for use on the 2.2 Litre Engine.

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 units with new Clutch
Housing. It carried over the R/H shift lever. It had synchro on Reverse Gear and 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) w/different Axle &Gear Ratios - not suitable for 2.2 Litre Engine Torque.

In a nutshell the 026 & 027 Gearboxes are very similar except for the Clutch Housing, Synchro on Reverse, 5th Gear Ratio. The clutch Housings & Rear Cover (with shift lever) can be changed over easily. Minor improvements were introduced at the time of Sport 350 to improve durability.

The Lotus versions of the Box were very similar to Renault units at first sight. What people do not realize is that the Lotus versions had some very important differences. The main issue is the crown wheel & pinion. Although the Ratio is identical to some Renault vehicle applications the material is different. The Renault material will not survive the Lotus application (even the earliest non intercooled cars). Running on the approved oil is another critical item.

Basic History of UN1 Gearbox

UN1-016 -- Original Esprit application -- 315 Nm (232 lb-ft)

1988, DOM/ROW intro, 1989 Fed Intro, left side shift translator

UN1-026 -- Esprit Hi-Tork -- 400 Nm (295 lb-ft)

1993, intro, stronger case, right side shift translator

UN1-027 -- Esprit V8 -- 400 Nm (295 lb-ft)

1996, V8 bell housing, higher 5th ratio, synchro reverse.

1998 , a modified cross shaft for direct cable shifter .

Minor durability improvements with Sport 350 intro.

UN1-028 -- Esprit GT3 -- 300 Nm (220 lb-ft) WEAK!

1998, like 027 but with lower third & final drive ratios (1.41 & 4.11 ??).

CWP ratio not suitable for torque of the 910 or V8 (GT3 = 2.0 liters).


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