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American Automatics

Specialising in Classic American Transmission Rebuilding

What type of gearbox do you have?

Literally hundreds of different gearboxes have been produced over the years but they fall conveniently into particular groups for most old American cars. They generally evolve year by year, by each manufacturer, as developments occur. The most common types are listed below for your interest. It's not meant to be a definitive list and refers to rear wheel drive layout only. If your trying to identify your gearbox and you're stuck, email me pictures and I'll tell you what it is. 

General Motors family tree 

Powerglides - 2 speed originally cast iron typically found in 57 chevy's. a weighty lump but very reliable. Air cooled bellhousing

Aluminium Powerglides - still 2 speed but lighter - sort after for drag racing for their shear strength

TH350 - all aluminium 3 speed - very dependable and stands abuse - sat behind millions of 350 motors. 4x4 versions. Fails with neglect and old age.

TH400 - more of a big brother to the TH350 - very strong but heavy and saps more hp to drive through it. Stands 500hp stock, 1000hp with upgrades. They just go on and on forever - fitted to mostly big block motors and Jaguar V12's Ferrari's and Rolls Royce so that says it all really

TH700R4 - first evolution overdrive - 0.70 in 4th gear. Has a lockup convertor for extra economy. Suffers from 3rd gear clutch failure in stock form.

TH700R4 - second evolution - larger input shaft - other internal changes - still suffers faults in stock form but better than the previous.

TH200-4R - medium duty overdrive from the 80's - excellent ratio spread - Can live behind a big block with mods - multicase bellhousing

4L60 - a 700R4 renamed! - More internal changes - best box of the overdrive bunch - still can fail unless parts upgraded - can be ok for 500Hp

4L60E - electronic controlled version of above. ECU controlled gear changes. No good for old chevy engines without ECU's. Needs an aftermarket transmission control unit to function which can be £600.

4L80E - bigger brother of 4L60E and electronic equivalent of TH400. Strong with overdrive. Bentley worthy big beast. Again dumb without an ECU.

Ford family tree

FX and MX -ford-o-matic / cruise-o-matic - yep! err?*! Early auto's best left in the scrap yard really.

FMX - evolution of above 2 types - Guts of an MX in a FX case. Alloy bell with cast iron case. Heavy.

C4 - 3spd - All aluminium - separate bell housings - 2 types, case fill (smaller) pan fill (larger) - fitted to everything you can think of due to the multiple bellhousings. Strong and reliable, only fail with age. Caution when interchanging parts like bell/ torque/flexplates! Some stuff just doesn't go!!

C5 - oilway modified slight variation of C4 - valve body mods - otherwise the same animal.

C6 - Big bruv to C4 - All Aluminium - Heavy duty like a TH400 - uses more HP to drive but stands abuse - best behind a 390 / 428 in a full body.

AOD - first 4speed - All Aluminium - weighty box - meaty parts - clever dual input shaft does not rely on lock up converter but does 'lock up'. Complex!

AODE - Electronic version of above - needs ECU to function like a 4L60E.

Chrysler family tree

Powerflite - 2spd - Cast iron - no park setting so don't forget the handbrake!!

Torqueflite - A904 - light duty 3spd - All Aluminium - reliable - mostly used on 6 pots

Torqueflite - A727 - Heavy duty 3spd - All Aluminium - this is the common box found in a ton of Mopar cars like the Dodge Charger. Strong and dependable behind a 440. Also used in Jensen Interceptors.

Torqueflite - A518 - overdrive version of above 727.

Torqueflite - A618 - Electronic overdrive version of 727

Buick / Olsmobile / Cadillac

Although really part of the GM tree these deserve an entry of their own

Dynaflow - Cast iron 2spd - damn strange - 220lbs!! weird dismantlable torque converter - short but wide - strickly in your 50's Buicks

Hydra-matic - 4spd - ditto weighty lump above - even heavier. 50 /60s Caddy's Old's. Not for the faint hearted to take apart.

Jetaway - 4spd - 50/60's Cadillacs - all these boxes are becoming hard to find parts for and those parts price themselves accordingly!