4L70E Wont Shift Automatically
Thread Starter
Staging Lane
Joined: Nov 2010
Posts: 71
Likes: 0
From: West Texas
4L70E Wont Shift Automatically My son has an 07 VortecMax Pickup, When you put it into drive it wont move. If you manually shift it, it does fine. You also have to downshift it manually. It is stock and nothing has been done to it. He said he didnt notice any Engine lights on for a code to be set. Im more familiar with the old three speeds, i would say Governor. I wouldnt think the clucthes are bad if it does fine manually. Any ideas?
He could have rolled the sprag. When you manually select a lower gear it applies the over-run clutch. It will only work like this for a short while before it smokes the over-run.
It is more than likely going to have to come out for a rebuild/repair
It is more than likely going to have to come out for a rebuild/repair
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Yes, it sounds exactly like a broken forward sprag. Here are some similar threads:
https://ls1tech.com/forums/automatic...-problems.html
https://ls1tech.com/forums/automatic...ear-drive.html
When the forward sprag fails it sprays metal pieces all over the place. This unfortunately requires not only a trans rebuild, but the converter will need to either be replaced or at least sent to a converter shop to be opened and throughly cleaned. You CANNOT just flush a converter. Finally, any separate trans cooler needs to be replaced and cooling lines flushed. If you try to skip any of these steps, the replacement trans will likely fail too because any hidden metal particles can jam a valve or cut a seal.
Sorry to give you this bad news.
https://ls1tech.com/forums/automatic...-problems.html
https://ls1tech.com/forums/automatic...ear-drive.html
When the forward sprag fails it sprays metal pieces all over the place. This unfortunately requires not only a trans rebuild, but the converter will need to either be replaced or at least sent to a converter shop to be opened and throughly cleaned. You CANNOT just flush a converter. Finally, any separate trans cooler needs to be replaced and cooling lines flushed. If you try to skip any of these steps, the replacement trans will likely fail too because any hidden metal particles can jam a valve or cut a seal.
Sorry to give you this bad news.
