Hard Shifts from 1-2, 3-4 and P to D

Drewsdmax

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Jul 16, 2012
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So this is a recent problem (2 days ago), i haven't modified my truck in like 6 months so its not a tuning issue as far as i know. All of a sudden it's been shifting pretty hard from 1st to 2nd at partial throttle, it's almost like it revs up a bit, then hammers in gear. 3-4th is similar but not quite a noticeable, and 2-3 and 4-5 are super smooth like it was before. Even when i shift from park to drive it jumps pretty hard, but not into reverse or neutral. on a side note, when i shift back to park from reverse it makes a loud clank sound, which also never happened before.
I changed the fuel, oil, and spin on filter about 3 weeks ago, and all the fluid levels seem fine. I'm kinda at a loss, and thinking of bringing it in to get it looked at. No codes either? Any input would be great, thanks

Here is a video of the sound from R to P (1/2 way through the video):http://api.viglink.com/api/click?format=go&jsonp=vglnk_jsonp_14023573981698&key=5d6502d39d69ed43baae82b0e2e9a891&libId=9bfcb877-59c4-49b0-9013-2eccb4e23020&loc=http%3A%2F%2Fwww.duramaxforum.com%2Fforum%2Ftransmission-shop%2F436970-hard-shifts-1-2-3-4-p-d.html&v=1&out=http%3A%2F%2Fs454.photobucket.com%2Fuser%2Fandrewc56%2Fmedia%2FIMG_1830_zps78759b88.mp4.html&ref=http%3A%2F%2Fwww.duramaxforum.com%2F&title=Hard%20Shifts%20from%201-2%2C%203-4%20and%20P%20to%20D%20-%20Chevy%20and%20GMC%20Duramax%20Diesel%20Forum&txt=IMG_1830_zps78759b88.mp4%20Video%20by%20andrewc56%20%7C%20Photobucket
 

Drewsdmax

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Jul 16, 2012
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No codes, had it at the mechanic on Tuesday, reset the taps but didn't really help. 3-4 shift is getting worse and slams into gear now. Talked to the builder, who is a 2 hr drive away, and he said I should do I line pressure test??? And probably a stuck valve or solenoid problem?
Is the spring in the trim valve something that is easy to change out? It's just hard to find a place around here that know about Allison's. Anyone recommend a good shop in Calgary?

Thanks for the reply.
 

Drewsdmax

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Jul 16, 2012
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This is probably a dumb question, but if it was a broken spring on a trim valve or stuck valve could this be repaired without removing the tranny? I ask because I know if you put on a transgo shift kit (which it has), the tranny has to come out... Thanks
 

Mike L.

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Trans only has to come out to install full Transgo kit because of the C2 piston mods in the front rotating assembly. The controls are in the valve body. Sounds like a spring problem in the A trim valve in valve body.
 

Drewsdmax

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Jul 16, 2012
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Thanks a lot Mike, I'll try and make some time to have a look at it. Really appreciate the input. If I find anything, I'll keep u posted (might be a little while).
 

Drewsdmax

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Jul 16, 2012
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Update: So I pulled the valve body out last night and checked out the trim valves and springs. And what do you know? The small spring above the check ball in the B-trim valve was collapsed pretty good. I have a pic, but can't upload it right now. I put everything back together with a new transgo jr kit. I only drove it about 5 km last night after filling it up with fluid, but it shifts pretty damn hard still, which I guess is expected.
Can I get away with not doing a relearn and just take it easy for a few days? I have a 6 hour drive ahead of me, all highway. Also, how long typically should the "smoothing out" process take with something like this....? I just hope that was my issue!

Thanks for the help fella's
 

Mike L.

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Aug 12, 2006
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It will eventually learn the hard shift out. At this point it really needs the Fast Learn procedure done with a Tech 2. You should be ok after a while but it will take some time as it is in slow learn.