OK, a little background:

1989 Corvette (duh) rebuilt 383 stroker 400+ est crank hp. 700r4 trans, stock style rebuild with transgo 2+3 shift kit (manual vb optional) and 2400 stall. 6600 miles on package, trans fluid and filter were changed at 1000 miles.

You may recall the last post I had on the trans with a bogging issue. The consensus was my stall with a low mph shift into 3rd was causing it, which I agreed with. If you recall, I also mentioned a harsh 1-2 shift at that time. It was pretty much always present since the rebuild.

The other night I backed into the driveway instead of pulling in. When I left in the morning and pulled straight forward, I noticed the 1-2 shift was very "soft" compared to normal. It was pleasant, and quick. Normally the 1-2 shift is hard and there is about a 1/4 second delay before it kicks in. I just chalked it up to the shift kit. There are no hard shifts from 2-3 or 3-4.

So yesterday I was able to do some testing in a parking lot. I was able to recreate the results about 90% of the time. Slightly more pronounced when the fluid is cold, but still there when it's warm. If I back up 20 feet in reverse then put it in 1, the trans and car "jerk" forward a bit. Start driving with mid-throttle and the 1-2 shift hangs and bangs. Put it in park for about 15 seconds, then go forward and the 1-2 shift is softer. Trans still loads up a bit and jerks forward in 1. If I put it in OD, the jerk isn't as pronounced.

I was reading and possible causes I found with similar complaints were a worn reverse input drum, broken accumulator spring, worn accumulator bore.

I don't think the spring is broken because that usually causes no 1-2 shift at all. It seems likes something inside is binding...like a clutch band, bore, spring, etc.

I don't know enough about transmissions to make an accurate assessment at this point.

Once I get my garage space back I think I'm going to pull the 1-2 accumulator housing off and inspect the bore and spring.

Any thoughts are appreciated!

Matthew

Hope it's easy.

If it's not the spring/bore, it's a rebuild, right?

I dunno. Pete mentioned little pieces of junk in the valve body itself can cause shifting problems as well. But since I can recreate this problem it doesn't seem like a random piece of clutch trash/metal shaving.

Matthew

Oh, as far as the rebuild I won't be doing that now. It still works fine, just a harsh shift. If it's a worn input drum then when I eventually do a rebuild that's a hard part I will replace.

Now your only problen is moving the landscape rock outa the garage.

If it jerks and bangs going into forward either 1st or OD, maybe check the C-Beam bolts make sure they are tight.. I know that will not be the answer to the whole problem nessacerily. But just an idea.... It's possible you have a sticking valve or an issue with an accumulator, or maybe the splines on one of the drums is worn though I would tend to think temperature would play more with a valve issues then a clutch pack sticking. That's just my guess as I am not a trans expert, though I've built a few 4L60E's.

-=Rick

Quote:

Rock is done...now it's left over garage sale crap!

Thanks, Rick. I'll double check the c-beam but it doesn't feel like that when I'm driving the car. I'm still leaning towards the 1-2 accumulator as my first point of attack.

Matthew

The 1-2 accumulator is the cushion (or shock absorber) for the 1-2 shift.
The aux valve body's job it to provide shock absorption of the park to drive shift, park to reverse shift, or drive to reverse shift.
Although I have never seen an aux valve body bore worn, it is worth inspecting. It is more common for trans builders to reuse a worn accumulator piston. This is a bad idea, as the center hole that rides up and down the hardened steel guide rod wears out the pistons.If the pistons are dated, replace them. Replacements are not date stamped.
I still think your problem is in the main valve body.
If none of the above solves it, I would gravitate towards the input shaft teflon seals as being a strong possibility. Especially if the builder used the scarf cut type seals.

Thanks, Pete!