transmission issues
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 45
Likes: 0
transmission issues
hello. I am new here and just bought my first vette two years ago and have loved working on it. I since have an issue with the transmission. I have the 79 L48 with Auto(not sure which trans, i was told TH350). this past summer i drove it quite a bit and then one day i fired it up to drive and it barely moves. I hit the gas and it wont speed up. it took the vette until 3rd gear to start really moving at which point i can speed up and drive normally. Until that point however it will shift but wont move very fast. Last year i replaced the transmission filter(not sure the history of the vette and when it was done before that) and im worried it might be the entire trans. Any tips? im about to replace the filter again. I have a small leak where the shaft goes into the trans but the fluid level showed full no matter how much leaked while it was stored for the winter. Any help would be awesome. Thank you!
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
Not sure. I have the same car and transmission. Whenever I had problems with the car not moving it was because my fluid was low (I also have a small leak). I know someone will chime in and know the exact answer, they have been helping me for 4 years now.
Welcome to the club, hope you enjoy working on it and spending money on like the rest of us.
Dan
Welcome to the club, hope you enjoy working on it and spending money on like the rest of us.
Dan
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
You are checking the tranny oil level when the engine is running and warm, aren't you? Checking it with engine off will always show that it's full....well, it'll show that it's overfilled. Your symptoms could be due to many things, but one of them is "low oil level". If that's not it, your problem is likely to be internal with worn/damaged clutches.
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
Welcome to the forum. If you determine that it is time for a rebuild you may want to think about a 700R4 or 2004R transmission swap. It'll give you a fourth gear and better highway mileage. I'm with the others fluid would be my first thought.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
Likes: 6
From: Austin Tx
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Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
As long as the fluid is at the proper level and looks/smells normal (not dark or smells burned) then it sounds like a weak pump or a dying torque converter. Modulator controls low speed high vacuum shifting so if the hose is off it will upshift like you're holding the pedal to the floor. A clogged filter will usually cause a whine and weak shifts. A sticking pressure valve will also cause the problem you have as will a loose valve body. Too much to diagnose this way. Have a competent mechanic pressure test it.
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
5th Gear
Joined: Mar 2011
Posts: 5
Likes: 0
From: California, Southern
Ok, so I got new tires and pushing 99 when the tranny slips out of gear!
I just got the car and after stopping at the nearest Napa Auto Parts, I check the tranny level. It's two inches over full and I limp home in first and sometimes second gear. What a bummer! OK! This week she's going into the air in the garage.
My Question, besides a general service and checking valuum lines, what is there to look for when opening the bottom? Thanks!
My Question, besides a general service and checking valuum lines, what is there to look for when opening the bottom? Thanks!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Metal debris in the pan. Any solid/hard metal parts/particles are an indication that a mechanical failure has occurred. Normal pan material is blackish, sludge like material which is a mixture of tranny fluid and abraded clutch plate material. The 'offical' [GM] name for that stuff is "swarf" and is expected to be found in the sump of an auto tranny.
The Dexron flluid should also smell sort of "sweet"; if the oil smells burnt, you probably have one or more "fried" clutches.
The Dexron flluid should also smell sort of "sweet"; if the oil smells burnt, you probably have one or more "fried" clutches.
