77 L48 Auto Slips in revers when cold.
Thread Starter
2nd Gear
Joined: Jul 2008
Posts: 2
Likes: 0
From: Buffalo NY
77 L48 Auto Slips in revers when cold.
Recently I purchased my first Corvette, a 77 L48 Corvette with an automatic transition. I am new to Corvettes so please excuse me if this is a stupid question or hopefully a simple fix.
When the car/transition is cold and I put in in reverse it will slip for 5-30 seconds than grab. Once it grabs I can put some pressure on the gas without a problem. After I drive it I can go into reverse without issue on flat ground. My driveway has an incline to it and it will occasionally slip a little backing into the garage. The car seems to shift fine in all other gears. I checked transition fluid and its dead on. What should I check next?
Also my dip stick is loose where it attaches to the motor. I hear this is a common problem. Whats the best way to fix it. I didn't want to start a new post on a dipstick question.
When the car/transition is cold and I put in in reverse it will slip for 5-30 seconds than grab. Once it grabs I can put some pressure on the gas without a problem. After I drive it I can go into reverse without issue on flat ground. My driveway has an incline to it and it will occasionally slip a little backing into the garage. The car seems to shift fine in all other gears. I checked transition fluid and its dead on. What should I check next?
Also my dip stick is loose where it attaches to the motor. I hear this is a common problem. Whats the best way to fix it. I didn't want to start a new post on a dipstick question.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
When you checked the fluid level was the engine hot and RUNNING? The engine must be hot and running to get an accurate fluid level. Clarify this and we'll go from there.
As for the dipstick, is it loose at the transmission or where the tube tab bolts to the bell housing. If it's loose at the bell housing then the bolt itself might be loose and you simply need to reach down and tighten it. At the same time, if the tube is loose where it stabs into the transmission you may need to remove the dipstick, and bend the tube tab so that when it's inserted and bolted to the bell housing it holds itself in tight. When you remove the dipstick, check to make sure the O-ring is in good shape.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Okay if the fluid level is fine then next check the vacuum line from the engine to the vacuum pod at the transmission. I have had several '77 Vettes and all of them had a cracked and loose vacuum line down at the transmission. It transitions from metal to rubber and that rubber gets soaked with oil over the years and cracks. Without good vacuum the transmission won't operate correctly.
The bottom end of the dipstick is probably just caved in a bit. You should be able to remove it o inspect it but an option aside from replacing it would be a high temp silicon coating the part that gets inserted. Let it cure for at least 24 hours before starting the engine, and don't slop so much on that it'll drip down into the pan.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If you have no slippage in any of the forward gears, you must have some internal leakage problem in the transmission. The reverse range still uses the same clutches as the forward gears. There must be a leak path somewhere in the reverse shift valve circuit which applies the appropriate clutches. Low apply pressure (due to internal leakage somewhere in that circuit) would allow a 'good' clutch pack to slip.
