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Trans slips when trying to pass...

LS2 BLAZER

LS2 BLAZER

New member
ok everyone, 2001 GP GT 125,xxx miles on her... been in the family since she had 3 miles on her...

i recently took it off my moms hands for a DD since i have a TBSS as my toy... one thing i notice, while driving normally, the car shifts perffectly fine.. no issues, no slipping, nada.... but if i try to floor it, like say trying to merge onto a highway on the on ramp, or trying to pass someone on the street, the tranny starts slipping.. it will stay in the power band right up until the shift point, but when i goes to shift... vrrrrooooommmmmm it just sits and doesnt shift.. but this is only when trying to pass or "goose" it.. if i let off the gas once it slips, and the rpm's drop, it will shift into the next gear... again, while driving normally, keeping the rpm's between 3-4k, it will shift fine...

any ideas on what could be going on??
 


Does it matter that one was done 25k miles ago? Kinda was included in a 100k matinenace package at the dealership at the time

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Did they flush it or just do a pan drop? If it was flushed that's not to good on it but i can't see it being a problem 25K miles later. Check your fluid it could be a little bit low.
 
dsmuts said:
Did they flush it or just do a pan drop? If it was flushed that's not to good on it but i can't see it being a problem 25K miles later. Check your fluid it could be a little bit low.
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The did a flush and filter change, so yes a pan drop as well... fluids are ok as I jus got my oil changed last week.. no visual leaks either.. do these trannies have a passing gear in them?

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Not sure what you mean by passing gear. Your trans should downshift to pass. I'd put a bottle of lucas in it with a fluid and filter change. It's supposed to be done every 30K anyway so your getting close.
 


dsmuts said:
Not sure what you mean by passing gear. Your trans should downshift to pass. I'd put a bottle of lucas in it with a fluid and filter change. It's supposed to be done every 30K anyway so your getting close.
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Yes it downshifts, but then when it goes to shift to the next gear, it slips... but only under stress..

And 30k miles for a stock gp gt tranny service? That's odd... but its a starting point and cheap enough to give it a shot.. if the tranny goes, I might as well junk the car.. the price of a tranny and install would out weigh my efforts to keep the car

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Is the slipping when it tries to shift from 3rd to OD? If so then I fear you are slowly loosing OD. The splines on the end of the shaft that engages OD is not hardened and as time goes on they wear down and eventually won't engage the 4th clutch hub. Then you will be running about 2500 or so at 60mph. I drove my 00GT this way for at least 2 years before I replaced the trans. and it was still shifting fine, except no OD.
 
FordMan77 said:
Is the slipping when it tries to shift from 3rd to OD? If so then I fear you are slowly loosing OD. The splines on the end of the shaft that engages OD is not hardened and as time goes on they wear down and eventually won't engage the 4th clutch hub. Then you will be running about 2500 or so at 60mph. I drove my 00GT this way for at least 2 years before I replaced the trans. and it was still shifting fine, except no OD.
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Thx for the input.. I don't think that's what's happening... when the TC is locked and I'm at cruising speed (say 65 mph) and I go and try to pass someone or "drop the hammer" as they say, on the gas pedel, the TC will unlock (downshift I guess you could call it) then the car will pull, but at the top of the power band, right before it goes to shift into the next gear (mind you, my foot is still to the floor), boom.. no shifting... while driving normally, it will shift perfectly fine... and at cruising speed (65 or higher) it is fine.. I just took her for a 6 hour drive accross state last month and got 28.2 mpg's and I believe the rpm's were at or under 2000.. so I don't think its OD... but I could be mistaken, I am very unfamiliar with these trannies.. I'm used to my 4L70e's and newer lol...

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Could be as simple as cleaning the maf and checking the TPS. Might be an issue in the trans. If you hit if from a stop, does it have trouble shifting from 1st to 2nd?

If you are at highway speeds, heading uphill and give it some throttle w/o downshifting, does it slip? Does it slip if it's at any other throttle other than wide open?
 
BillBoost37 said:
Could be as simple as cleaning the maf and checking the TPS. Might be an issue in the trans. If you hit if from a stop, does it have trouble shifting from 1st to 2nd?

If you are at highway speeds, heading uphill and give it some throttle w/o downshifting, does it slip? Does it slip if it's at any other throttle other than wide open?
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Yes the issue is there from first to second from a stop if I goose it, but at half throttle to quarter throttle (when rpm's stay between 3-4000 rpm) the tranny shifts fine...

And no it doesn't slip w/o downshifting....at quarter throttle and sometimes even half throttle there is no slipping either.. but foot to the floor or almost foot to the floor, she slips everytime...

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Do you feel it slip in the gear at wide open or just doesn't seem to shift?

Slipping in gear may be input piston etc or clutches, at the shift.. like it just won't shift may be more electronic.
 
BillBoost37 said:
Do you feel it slip in the gear at wide open or just doesn't seem to shift?

Slipping in gear may be input piston etc or clutches, at the shift.. like it just won't shift may be more electronic.
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At wide open, there is no shifting at all... it just sits and revs between 4000-4800 rpm's with a ticking sound... once I left off the gas, it shifts...

I made 3 videos, one of normal driving and shifting, one of normal driving, then punch it and it won't shift, then one from a stop to WOT and it won't shift.. they are uploading to youtub right now, so I'll post when they're done

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That is definitely slipping. I'd do a pan drop and filter change with a bottle of lucas stop slip.
 
Pure2sin said:
Suggestions:

PCS Pressure control solenoid

Bad torque converter??
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where is this PCS located and how can it be diagnosed? And obviously i would have to drop the tranny to get the TC.. im just looking for a cost effective way on this for now.... hopefully its not looking like i need a new tranny...
 
I would have to say that is not a transmission issue.... Most likely a misfire etc, because it should have revved out to 5500 rpms and about 40mph in first gear when flooring it. If it never gets to 5500 it wont try to shift, and it wont make "slipping trans misfires noise".
 
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