transmission banging into second

I have a 96 chevy van w/350 engine and automatic. I let it set for about 3 months and decided to drive it the other day. When it shifts into 2nd gear it shifts really hard. Before this it was shifting perfectly. I changed the fluid and filter and of course that didnt help. Any suggestions?

 

Good chance you have a tranny about like the one in my '94 wrecker (GM 4L80E). If so, when mine starts slamming the 1-2 shift it's because the input speed sensor has gone south.

 

Yes, it is the same transmission. Does that fix it with yours? Are they expensive and hard to change?

 

A broken accumulator spring will cause the same effect. I have seen that happen to trans. that sit for awhile. Most of the time it is from sitting longer that yours did. It may have going bad anyway.
Just a thought.

Travis

 

The speed sensor runs about 50 bucks I think. I actually carry a spare around in my glove compartment, although I haven't had one crap out in quite a while (knock on wood). Every once in a while I'll get a semi-hard 1-2 that I can fix by turning the key off and then restarting. I've got some quirky wiring doing that.

The speed sensor is on the left side of the tranny housing and has one bolt I think and a wiring connector, but there are two sensors there and I'm trying to recall which is which.

I can get tranny error codes when I pull codes, not sure if you can or not.

 

I replaced both speed sensors and still same thing. FYI they are only 19 bucks at Oreilly in case you need to buy anymore. Anyone else have any suggestions? As for reading codes, this is a 1996 model but is OBD1 and the code I pulled is 73. From what I have looked up, is transmission pressure control solenoid. Anyone know if this will cause hard shift from 1st to 2nd?

 

I don't know, but at this point I would think an error code in the tranny would pobably put you on the right track, but of course codes often don't point directly at the bad part. Probably going to need some professional help; any good tranny shops in your area?

When I'm out and around tomorrow I'll try to quiz my tranny guru on it and see what he thinks.