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Keane165's 1970 LeMans

2022 June
of the Month

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Vin information

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The VIN will not tell you what transmission originally came with this vehicle, only the engine. For that you will have to order the paper work from Pontiac Historical Services (PHS). I would expect it would mostly likely have been built with 350TH 3-speed automatic transmission. However, it is possible, albeit rare, to have a manual 3-speed with a 301.

You VIN breaks down like this:

2 = Pontiac Motor Division

K = Grand Prix car line

37 = 2-door sedan

Y = 301 Pontiac 2-bbl engine

9 = 1979 model year

P = Assembly plant - Pontiac Michigan

610552 = assembly sequence number at Pontiac Assembly

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A 305 is doable. It was emissions legal for California in 1979 in the Grand Prix. So those parts like motor mounts and exhaust manifolds should be available. The 700R4 requires more work since overdrive transmissions didn't come into their own until the 1980s. 

A 700R4 case is longer than a 350TH. So you will have to shorten your drive shaft accordingly and may have to move your transmission cross member back to compensate.

The other big thing to worry about with the 700R4 is installing a TV-cable (throttle valve cable), which is a cable that connects your engine (e.g. carb) to your transmission in order to tell it when to shift.  

Other things to at least look at and evaluate:

1. Move/relocate/change the length of your emergency brake cables and/or brackets because of the transmission swap

2. Determine your rear axle ratio: is the stock ratio too tall with the overdrive transmission? If you have a stock rear end that is close or under 3.0:1, then you should consider moving to something like 3.31:1 or 3.55:1. A 2.73:1 gear may bring your engine revs so low that is will hard to sustain highway speeds.

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