Transmission locks up when it shifts

[Jim_4506]

When transmission shifts from 1th to 2nd and 2nd to 3rd it locks up the rear tires for a second or so and then frees up. Tires stop, it’s a posi, springs buckle
Then car continues to drive. Till it shifts to 3rd and does it again. Afraid to keep going. Ideas?

 

[thomas lauber]

When transmission shifts from 1th to 2nd and 2nd to 3rd it locks up the rear tires for a second or so and then frees up. Tires stop, it’s a posi, springs buckle
Then car continues to drive. Till it shifts to 3rd and does it again. Afraid to keep going. Ideas?

 

[thomas lauber]

sounds like a band adjustment issue

 

[1 Wild R/T]

sounds like a band adjustment issue

Yes & no... It's a shift timing issue, which band adjustment does effect.... Has the car had a shift kit installed? If so the orifice in the front clutch passage needs to be smaller...

As Thomas mentioned band adjustment can cause it and it's certainly worth checking the adjustment... But backing the adjustment off to far isn't good either...

The adjustment on the drivers side outside the trans is 2nd gear, typically you loosen the lock nut run it in till it gets snug, torque it to 72 in/lbs then back it off depending on engine size somewhere between 2 & 3.5 turns... I'd crank the lock nut loose & try loosening it 1/2-3/4 of a turn to see if it helps..

 

[khryslerkid]

Does the radio turn off?

(Sorry, couldn't help mysf.)

 

[steve340]

I would remove that transmission immediately. If it stays in two gears at once you could blow the back off the motor and lunch the trans and diff all in one go.

 

[1 Wild R/T]

I would remove that transmission immediately. If it stays in two gears at once you could blow the back off the motor and lunch the trans and diff all in one go.

It's called shift overlap, it can be fixed... You either slow down the application of the the component being applied or speed up the release or the component being released...

Honestly a flow restrictor or a band adjustment could solve it...

Or you can just remove the transmission immediately...

 

[steve340]

What you describe seems far from common.
I would be to scared to even move my car if it did that. If you have the knowledge fair enough - if you don''t get some help.

 

[RT K_line]

Put a manual shift valve body and be done. You won’t regret it.

 

[miller]

Almost sounds like the band adjustments got torqued down, and somebody forgot to back off the adjusters.

 

[RT K_line]

Ok I reread your post and need more info. Does it happen at any speed or throttle position. Meaning if you take off like a granny and let it upshift at 18 and then around 25mph does it still do it? Could be getting a 2nd and 3rd gear scratch, as it called. But usually happens under acceleration. I do agree with most above about checking basic adjustments first. Did it jut start out of the blue?

 

[steve340]

Have you checked the rear axle to make sure that is all working correctly?

 

[Jim_4506]

Ok I reread your post and need more info. Does it happen at any speed or throttle position. Meaning if you take off like a granny and let it upshift at 18 and then around 25mph does it still do it? Could be getting a 2nd and 3rd gear scratch, as it called. But usually happens under acceleration. I do agree with most above about checking basic adjustments first. Did it jut start out of the blue?

Yes out of the blue. I put it on my two post lift yesterday and ran at low rpm and when it shifted to 2nd and also when it shifted to 3rd it locked up for a second and then released. Tires came to complete stop and leaf springs tried to wind up. Once in third never locked up again. Car has wild 600 plus HP 440 with 410 posi. About 1000 miles on build. Double pump 727 with two shift cables, one for forward and one for reverse and park. After this happened, one of few times I took off like granny, I have not made a hard start or shift. Locks at low rpm automatic shift. Has major shift kit and clutches, rebuilt when building car. Put a Hughes 3000 stall converter in it new last year.

 

[RT K_line]

Does the converter still stall as it should on the ground? Did you just notice it when it was on the lift or did it happen while on the road? I had-a Hemi superstock unit ordered from direct connection back in the day and it would try to jump off the jack stands when it shifted. It jumped 1/2 a car length on the one two shift on the ground too. Have you checked the cable adjustment? Something may have moved. Especially since it’s a new build with basically shakedown miles.

 

[Jim_4506]

Does the converter still stall as it should on the ground? Did you just notice it when it was on the lift or did it happen while on the road? I had-a Hemi superstock unit ordered from direct connection back in the day and it would try to jump off the jack stands when it shifted. It jumped 1/2 a car length on the one two shift on the ground too. Have you checked the cable adjustment? Something may have moved. Especially since it’s a new build with basically shakedown miles.

Locked up the rear wheels when I was driving it as it shifted. Locked up wheels yesterday on the lift with low speed shift also. Looked at cables on tranny and one is locked in position with a both thru a hole on cable adjuster (no movement possible there). Other cable is tight and does not appear to have moved. Will look at connections on console sifter Monday or Tuesday as major car show here this weekend.
I will do band adjustment next week. Thanks for the input.

 

[Dipstick]

1-2 overlap is pretty common when manually shifting with a stock rear servo, when auto shifting there should be no overlap.

2-3 overlap can be cured with a simple restrictor orifice.

 

[1 Wild R/T]

1-2 overlap is pretty common when manually shifting with a stock rear servo, when auto shifting there should be no overlap.

2-3 overlap can be cured with a simple restrictor orifice.

Exactly
When left in drive theres nothing that needs to release when shifting to 2nd.. The sprag is holding & immediately allows the drum to overrun.....

Manual first gear the band is applied & needs to release to shift into 2nd...

2-3 overlap is the kick down band failing to release as quickly as the front clutch applies... So the restrictor goes in the front clutch apply passage...