TH 400 Gear sets

[Thomas Alberts <talberts@aero.odu.edu>]

For Kirby and whoever else may be interested in this, there are
apparently several sources for modified planetary gearsets for the 
TH400 transmission.  These include John Kilgore in Burbank CA
and TCI.   As far as I can establish, there is no factory
gearset for any TH400 that provides anything other than the ratios
that come in the XJ-S.  Those are 2.48:1 first, 1.48:1 second.  I
have seen listings for "straight-cut" gears for these transmissions,
that I believe fit the existing planetary carrier, but have not been 
able to establish for certain what gear ratios these produce.  Some 
people seem to believe they modify the gear ratio, others, including
John Kilgore, say no.  Straight cut gears apparently came in some 
heavy duty applications like ambulances and the likes.  In any case 
they would surely be louder than the angle cut versions, and thus 
perhaps not of interest to Jaguar owners.
As I understand it, the typical performance modification is performed 
by removing one of the two gears from the sun gear, and either welding
or press fitting and keying on a sun gear from another GM transmission.
Kilgore says he uses a 0.003" press fit and a key in his.
The TH400 planet carrier is then modified to accept a mating set of planet
pinions and ring gear.  This produces a first gear ratio of 2.75:1 and 
second gear of 1.57:1 while 3rd gear, of course, remains at 1:1.  John
Kilgore says it takes 3 transmissions to perform the modification.
He uses part of the sun set from a Metric 200 transmision, and the
planet set from a TH350, in addition to the obvious TH400 parts.  Kilgore 
currently sells his gears for $375 but one of his distributors quoted me 
$485.  TCI sells theirs directly for $358, but I got a price of $325 
from one of their distributors.  Personally, I felt more confident in 
John Kilgore as he seemed more knowledgable about these gears than anyone 
I could get on the phone at TCI.  Turbo Action also says they manufacture 
such a gearset.  They quoted me a price of $536 but indicated that their 
distributors would sell them cheaper.  John Kilgore also manufactures a 
gearset that produces a first gear of 3:1, however they make fewer of 
these and the price is higher.

TCI and Turbo Action are listed in Kirby's book.  John Kilgore
can be reached at:

John Kilgore
412 South San Fernando
Burbank CA 91502
(818) 843-7180

In the recent discussions about GM400 transmisions, nobody has 
responded with any direct experience with these gears.  If 
anyone is out there that has anything to add, I would be
grateful for their input.

Thomas E. Alberts

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