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1995 5.7L trans am hard shifting at high rpm
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osiris5217
Novice
Sep 30, 2012, 10:12 PM
Post #1 of 11
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1995 5.7L trans am hard shifting at high rpm
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So I bought her yesterday, seems to be well maintained and ran on and off by a married man with four kids. The engine runs great no knocks or any noises. My problem is that when I go to give it some gas and it jumps to 4.5k rpms or so it shifts hard and sounds like someones dropping a 5lb weight on the car floor about midway in the car. I spose inbetween the front seats. It does this only in first to second gear shift, I checked the fluid; it's got plenty and the fluid has a good pink/red color to it and isn't burning. It doesn't drop hard into reverse or drive at all, smoothly actually. And it'll shift up and downshift fine, it'll shift at 2k rpms on a smooth takeoff no problem but once I get to about 4k rpms on a take off it'll jerk on the shift from first to second and making the noise previously mentioned. Every shift up from there is just fine but just 1st to second from 4k rpms and up will jerk hard and make a noise. Does anyone have any clues as to what it could be and if it's a serious issue I should get taken care of immediately?
The car has 140,000 miles on it and seems to be very well maintained, original everything and unwrecked.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 1, 2012, 4:53 AM
Post #2 of 11
(3419 views)
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Re: 1995 5.7L trans am hard shifting at high rpm
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Rule out things like engine and motor mounts. Didn't you check this car out at all before buying it?
T
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osiris5217
Novice
Oct 1, 2012, 1:22 PM
Post #3 of 11
(3383 views)
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Re: 1995 5.7L trans am hard shifting at high rpm
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Yeah I checked out all the fluids, looked for leaks/cracks under the front end after jackin it up and he said the tranny was just rebuilt so I wasn't concerned about it. I looked into the crank case, it was clean. I did check the motor mount when I was buying but not the tranny. I didn't crawl that far underneath it. I also didn't accelerate it hard when I test drove it haha, I figured it common courtesy to not rag it hard with the owner in the vehicle.
I just looked under at it after taking it to my towns oil change place and yeah the rubber tranny mount is slicing in two and being forced outward. I think that's the problem and I'll be replacin it.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 1, 2012, 1:45 PM
Post #4 of 11
(3379 views)
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Re: 1995 5.7L trans am hard shifting at high rpm
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If you can see that you know it's bad and probably the clunk. Even if not the whole problem it is a problem so do that. Motor mounts may appear fine until under load + looking at them or just with hood open you may notice engine moves too much doing what I'll call a brake stand (fighting engine with brakes without moving) for a second NOT to be done by anyone who doesn't know what that is about or how to do that safely,
T
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nickwarner
Veteran
/ Moderator
Oct 1, 2012, 3:56 PM
Post #5 of 11
(3365 views)
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Re: 1995 5.7L trans am hard shifting at high rpm
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Trans mount can certainly make a hell of a bang, but have you had the PCM scanned for any codes, specifically is a P1870 present?
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osiris5217
Novice
Oct 1, 2012, 7:47 PM
Post #6 of 11
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Re: 1995 5.7L trans am hard shifting at high rpm
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Yeah I just checked the motor mount while it was running in idle, I'll be sure to keep that break stand in mind.
And nah, it's not throwing any codes so I haven't scanned it, I'm gonna be replacing the mount tomorrow and I'll update you guys afterwards. The mount looked terrible so I believe it's the sole factor as the transmission shifts so smoothly afterwards it can be hard to tell when it shifts sometimes because it does it so smoothly and responsively.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 1, 2012, 8:41 PM
Post #7 of 11
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Re: 1995 5.7L trans am hard shifting at high rpm
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I meant back in post #2 to say engine and trans mounts. Got my knuckles rapped for calling an "engine" a "motor" - words that were abused so long ago nobody could be alive to remember!
Brake Stand: I said that so I'll finish what I mean better on that. It would be getting the car in a place where you have nothing to harm in front or back of it. Have parking brake set firmly and hold service brakes firmly as well. Open hood while just temporarily fighting engine with the car locked still looking at mounts from the side best not in front in case it took off. Takes a driver and a person to watch for the best view of course.
In forward engine would lift on one side and be putting force down on other and opposite that in reverse.
For trans mounts some you can see easily and some just a careful lift in known right spots will show one (more if more than one used) separate.
In this case you can see a problem. Codes as Nick mentioned would likely need a better scan tool and doubt would set a light on dash. No telling if more than just a mount lurks with some info.
If doing this/these mounts yourself use care where you support things, push or pry so no other items get damaged in just replacing them.
Good luck with it,
T
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osiris5217
Novice
Oct 1, 2012, 8:57 PM
Post #8 of 11
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Re: 1995 5.7L trans am hard shifting at high rpm
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Yeah things can go bad if that tranny drops haha but yeah I've done it a few times before. I've seen a lot of people complaining about trans ams going through tranny mounts regularly.. Might be due to the high torque people love and the oem daily driver mount. But I'm also going to be double checking the motor mount so its not causing the tranny to twist
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osiris5217
Novice
Oct 2, 2012, 10:07 PM
Post #9 of 11
(3308 views)
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Re: 1995 5.7L trans am hard shifting at high rpm
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Okay I replaced the tranny mount and yeah that fixed it very much so. The clunk is gone and it shifts a ton greater. I still think it could shift better though comin off first into second. Its still not 100% smooth but it's within a normal high rev shift on a take off with an automatic. I'm thinking at this point a valve or a solonoid could stand to be replaced, the engine mount is solid. I'm not so sure how I could detect it aside from jacking it up again and dismantling it though. Do you think this would be a good next step?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 2, 2012, 11:09 PM
Post #10 of 11
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Re: 1995 5.7L trans am hard shifting at high rpm
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I plead IDK what the OE plan was for a 1-2 shift on this at higher RPM. It is the most likely to be the most stressed shift with most. Car hopefully thought of some aggressive acceleration and some bragging rights. Abrupt shifting wastes less time plus if nothing plain breaks should be easier on the wearing parts of the trans.
The propensity for higher pressures from trans pump to have plenty of pressure to actuate the shift is good right then. Consider you also have some miles on this too. Any history of fluid change service on this? AYOR as if untouched changing it all out can either help or expedite its demise.
Granted it can be fun but this constant (if so) pushing 1st gear to 4-4,500 RPM for shifts to 2nd is going to take its toll. It wasn't meant to be a grocery-getter but it still is hard on it.
Motor/engine mount probably would be noticed as a unique feel of too much engine motion/twist upon acceleration or intentionally looking for it. Usually just one is bad if bad on the side that lifts with torque which is/was usually the driver's side mount,
T
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osiris5217
Novice
Oct 3, 2012, 7:37 AM
Post #11 of 11
(3285 views)
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Re: 1995 5.7L trans am hard shifting at high rpm
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It's not that I have to push it to 4.5k rpms its just that when I do the first to second shift can jerk the car some about like a manual transmission shifting, it does perfectly fine shifting; no hangs or noises or anything. Maybe that's how this car shifts? I've never had an automatic car with 320+ torque so I don't know how smooth an automatic can shift with that much torque dropping into second. It will shift through the other gears so smoothly you can't even tell its shifting. The tranny was just rebuilt, the bell house still has a fresh coat of silver paint, I would say within the past 30k miles. The fluid is perfectly colored, so I don't think the transmission is all gunked up or anything. I'll check out the engine mount again.
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