tranny

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Jul 25, 2010 | 07:17 AM

EARLY BIRD 18

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tranny

i have a 79 bronco and am new to the auto tranny can some one tell me why it go,s in drive smooth but go,s in reverse hard kinda slams.previous trucks had 4 speeds so don,t know much bout auto,s.

Jul 25, 2010 | 08:37 AM

Encho

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Joined: Dec 2004

Posts: 6,902

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From: Caracas, Venezuela

Hey there, welcome to the forum. Well, as with anything trannys wear out and eventually stop working the way they were designed too, maybe yours is already failing, but there are some considerations. Maybe you have low fluid levels, to check/fill that old tranny, you should use Dexron III or it's Mercon equivalent. Measure the fluid level while the truck is at working temp. and in Park, fill up if neccesary. Other cause for the Slam you are feeling could be worn out tranny/engine mounts, check those out, also check your U-joints/driveshafts for play. If none of those seem to be the cause, i would think your tranny is dying, it still will last a long time, so don't worry too much. Good luck.

Jul 25, 2010 | 08:19 PM

greystreak92

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Joined: Sep 2002

Posts: 9,182

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From: Gateway to the West

Check fluid level in the transmission and if needs be change fluid and filter. The C6 auto in your 79 is probably one of the single most reliable automatics Ford ever put in the trucks and it will put up with quite a bit of abuse but fluid level is fairly critical. If it only behaves this way going into reverse, I would tend to suspect this to be the problem.

However, if it slams gears or shifts hard in all gears, check the vacuum supply to the shift modulator on the tranny itself. Poor vacuum supply or a dying modulator will often cause hard shifting.