Car slips out of gear

[Premmontecarlo5.3]

Hi everyone,
I've been having and issue with my monte carlo for a few weeks now. It's 1981 monte carlo with a 2004 LM7 engine and a th350 transmission out of a 1987 monte carlo. When I go over a bump or accelerate too hard, Sometimes the car won't accelerate no more and just idle. But today it just started reving up to 1600-2000 rpm as well and out of gear. So I turned it on and off twice then it was fine again. What could cause this?

 

[Sweet_Johnny]

I'm a bit confused here. Are you saying that the shifter physically changes position and goes to Neutral? = Check shift linkage.

Or are you saying that the transmission is slipping while driving in gear? = Burnt clutches, bad pump, or bad converter. Rebuild/replace the entire setup.

Is this a th350C with a lockup converter? If not, turning the car off won't reset anything and the only way it would help is if things were too hot, in which case you'd have to wait a while for a change to occur. The th350 has a mechanical speedo, vacuum modulator, and a cable to drop a gear when passing: i.e. no electronics. The "C" model has a lockup style converter which I won't even begin discussing, but there's a solenoid that can become stuck and turning the power on/off can occasionally help. They're not incredibly common.

I hate to ask, but are you 100% sure on the transmission model the car has? An old friend of mine had this exact issue on a 2004R, which is an entirely different system. We'd sometimes have to kill the ignition while rolling down the highway.

 

[Premmontecarlo5.3]

I'm a bit confused here. Are you saying that the shifter physically changes position and goes to Neutral? = Check shift linkage.

Or are you saying that the transmission is slipping while driving in gear? = Burnt clutches, bad pump, or bad converter. Rebuild/replace the entire setup.

Is this a th350C with a lockup converter? If not, turning the car off won't reset anything and the only way it would help is if things were too hot, in which case you'd have to wait a while for a change to occur. The th350 has a mechanical speedo, vacuum modulator, and a cable to drop a gear when passing: i.e. no electronics. The "C" model has a lockup style converter which I won't even begin discussing, but there's a solenoid that can become stuck and turning the power on/off can occasionally help. They're not incredibly common.

I hate to ask, but are you 100% sure on the transmission model the car has? An old friend of mine had this exact issue on a 2004R, which is an entirely different system. We'd sometimes have to kill the ignition while rolling down the highway.

To my understanding, the transmission is a th350 not a th350c. I know when the transmission gets warm it'll start jerk from 1st to second, but now for some reason if I go over a bump and I press the accelerater it won't work and a couple of seconds later it'll work again. Today it started to rev to 1500 rpm and it wouldn't accelerate. I guess since I turned it off and let it cool down it started working again.

 

[Sweet_Johnny]

Sounds like it's slipping. Is the fluid low or burnt at all?

 

[Premmontecarlo5.3]

Sounds like it's slipping. Is the fluid low or burnt at all?

Fluid level it good, I just checked it

 

[Premmontecarlo5.3]

Sounds like it's slipping. Is the fluid low or burnt at would it be better to get it rebuilt? Because if that's the case, I wanted to install a 700r4 so I can have 4 gears instead of 3

 

[CopperNick]

Sounds like the friction disks in the first/second pack are about done. Had that problem with my old 78 and it got so bad that the box would start in first and then barely touch base with second while headed for third. About the only thing I didn't dump into the pan was pureed bananas!!

Thing for you here is, it is already warning you that it is a very sick puppy. So do you flog it until dead? or pull it for a rebuild? or pull it and plug in that 700R4, which is something I have done with another of my rides.

Being that you say your engine is a Vortec and an 2004 LM7 which is both a truck motor and technically an LS1/2 (GM style weirdness because in a car they were called an LS and the Trucks were termed Vortec. If your coils are mounted on the rocker covers then that is, for all practical purposes, an LS) What you might find when you go to unbolt that 350 is that you might only have 5 bell housing bolts to remove, not 6, or that there is a spacer/adapter in there that both bolts to the LS style pattern and offers the correct pattern for an earlier transmission. (Built 400 to an LS comes to mind)

Instead of the 700R4, if the block is an LS, then what about the 4L60? as an option??


Nick

 

[Premmontecarlo5.3]

Sounds like the friction disks in the first/second pack are about done. Had that problem with my old 78 and it got so bad that the box would start in first and then barely touch base with second while headed for third. About the only thing I didn't dump into the pan was pureed bananas!!

Thing for you here is, it is already warning you that it is a very sick puppy. So do you flog it until dead? or pull it for a rebuild? or pull it and plug in that 700R4, which is something I have done with another of my rides.

Being that you say your engine is a Vortec and an 2004 LM7 which is both a truck motor and technically an LS1/2 (GM style weirdness because in a car they were called an LS and the Trucks were termed Vortec. If your coils are mounted on the rocker covers then that is, for all practical purposes, an LS) What you might find when you go to unbolt that 350 is that you might only have 5 bell housing bolts to remove, not 6, or that there is a spacer/adapter in there that both bolts to the LS style pattern and offers the correct pattern for an earlier transmission. (Built 400 to an LS comes to mind)

Instead of the 700R4, if the block is an LS, then what about the 4L60? as an

To swap the transmission to a 4L60, what are some of the things I'll need to take into account?

 

[Sweet_Johnny]

To swap the transmission to a 4L60, what are some of the things I'll need to take into account?

The 4L60e is a newer version of the 700r4. Installing it will require a factory TCM (and accompanying harness) or a standalone control module to make it shift. = Expensive. That's in addition to a different transmission crossmember location and shorter driveshaft just to upgrade to any 4 speed O.D.. You may want different rear gears afterwards but its not absolutely necessary.

I agree that the clutch frictions in your th350 are dying but was hoping to find a smaller problem with an easier solution.

 

[Premmontecarlo5.3]

The 4L60e is a newer version of the 700r4. Installing it will require a factory TCM (and accompanying harness) or a standalone control module to make it shift. = Expensive. That's in addition to a different transmission crossmember location and shorter driveshaft just to upgrade to any 4 speed O.D.. You may want different rear gears afterwards but its not absolutely necessary.

I agree that the clutch frictions in your th350 are dying but was hoping to find a smaller problem with an easier solution.

I have a 7.5 rearend with 3.73 gears at the moment