1976 Tranny Slipping
Thread Starter
Cruising
Joined: Aug 2005
Posts: 12
Likes: 0
From: Ohio
1976 Tranny Slipping
Greetings,
My 1976 TH350 seems to be slipping. When I first start driving it is okay; at 70 mph the tachometer reads around 3500 rpm. After about 20 minutes or so, to maintain the 70 mph, my tachometer goes up to 4000 - 4200 rpm. Is this a tachometer problem or transmission problem? Also, is it the torque converter? I believe I have 3.08:1 in the differential and am running the stock 350 CI. I have replaced the transmission filter and fluid and added transmission "fix" fluid to it; the problem persists. Any suggestions will be appreciated...thanks!
My 1976 TH350 seems to be slipping. When I first start driving it is okay; at 70 mph the tachometer reads around 3500 rpm. After about 20 minutes or so, to maintain the 70 mph, my tachometer goes up to 4000 - 4200 rpm. Is this a tachometer problem or transmission problem? Also, is it the torque converter? I believe I have 3.08:1 in the differential and am running the stock 350 CI. I have replaced the transmission filter and fluid and added transmission "fix" fluid to it; the problem persists. Any suggestions will be appreciated...thanks!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Well, normally, slipping could be caused by low oil level. But, since yours works fine until it gets really hot, I suspect your oil level in the tranny might be too high. If you get too much fluid in an auto tranny, it starts "churning" and foaming up. The 'foamed' oil does not have the same frictional characteristics and can start slipping in gear. Recheck your oil level with the engine and tranny fully warmed up. Do that after you take it for a short drive, sometime.
Racer
Joined: Apr 2010
Posts: 291
Likes: 1
From: Lake Mary, FL
Instructor
Joined: Sep 2010
Posts: 218
Likes: 3
From: East Bethel MN
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Pull the tranny dipstick and smell the oil. If it smells 'burnt' [instead of having a 'sweet' smell], the clutch plates in one of the clutches are worn out and slipping when activated. Time for a rebuild or tranny swap.
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Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Sound's like it's time for a re-build, as the whining is usually a bad pump bearing and the burnt smell a bad clutch pack. If you can pull the tranny yourself, and take it to a shop for a standard bench re-build, probably save yourself some pretty good money. Risk is, if the shop messes up and doesn't road test afterward's, could turn into a real headache.