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Isuzu Impulse 3.90 Diff Gears | Opel GT Forum


Old Opeler
Joined Jun 15, 2003
5,564 Posts

Yep - the Imulse diff to use - or get gear parts from - was used right up to 1989 in RWD Non-Turbo Impulses and has a torque tube that looks very like Opel diffs (mainly because they were made in the same GM factory and supplied to both Isuzu and Opel - plus early years of Vegas, Astres and Chevettes - but with different lengths of driveshafts/torque tubes and disc brakes in Isuzu's case).

Turbo Impulses with auto trans used the same type of diff till about mid-1987 when it was found the 180ps from the turbo motor shredded them (thus the limit on hp that they can sustain - about 150/160 hp).

The opel torque tube bolts on to the Impulse housing and the Opel driveshaft slides on to the Isuzu barrel spline on the front of the pinion - so as long as the wider Isuzu diff fits your chasis and disc brakes are allowed in your racing class - the whole rest of the Impulse diff can be used in a Manta with a little spring cup and location bar alteration ... If you can find an early Vega or Astre or Chevette LSD unit (Aurburn made one!) that will fit too! Pic of a NOS one that was on EBay a couple of years ago attached below.

BTW: The Impulse front suspension is also very similar to the Manta/Ascona/1900 front suspension - and as an aside ... the Impulse front spindle can be fitted to the GT/Kadett front suspension with a 10mm spacer above the Opel top ball joint; with the Opel lower ball joint bolting up with the same taper as the Impulse one .... nice, light 246mm vented discs and Isuzu calipers on GTs and Kadetts!


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