05 GT problems with reverse

- Sometimes (about 30% of the time) when I put the car in reverse (auto trans) it goes extremely slow and when I give it gas it revs really high.
- If I rev it too much the car goes in to limp mode. Weirdly enough, when it's in limp mode, reverse works normally. (just have to restart car to get out of limp mode)
- It doesn't always happen and there is no rhyme or reason as to when the car is hot or cold, happens randomly either way.
- Throws a P0720 code (Output Shaft Speed Sensor Circuit) & a P2106 (Throttle Actuator Control System - Forced Limited Power). I ordered an output shaft speed sensor/vehicle speed sensor but that just seems too easy.

Anyone else have this issue? OR any other ideas?

Does it ever hang up or delay shifting from reverse into drive? How many miles since the fluid has been changed?

Solenoid block failure is common in these cars. That causes problems with reverse.
P0720 can be thrown from worn out fluid. Car is over 17 years old. Electrical connections start to corrode. Check them.

LAGA thanks for the top tip mine lags going to reverse sometimes not often but every once in awhile......I think the ambient temp may be the factor that determines when it does this. I think it could also be the fluid although it hasn't been forever since I changed it it has been a bit.

I haven't noticed a delay shifting from reverse to drive.

I don't know when the fluid was last changed unfortunately. I do know that when I got my last engine oil change they told me they weren't legally allowed to change tranny fluid in Florida if the tranny has over 100K miles (112K) and I'd have to go to the dealer.

ZwookY said:

..... they weren't legally allowed to change tranny fluid in Florida if the tranny has over 100K miles (112K) and I'd have to go to the dealer.

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WTF kinda BS is that? I've never heard of such a thing.

07 Boss said:

WTF kinda BS is that? I've never heard of such a thing.

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I don't know but I'd rather they say something like that then try it and mess it up.

Also, forgot to add:
When I am in reverse and it's working normally, if I go too fast I get a major vibration when I hit the brakes.
Definitely weird.
Hopefully it is just the sensor but I'm not holding my breath.
I'll find out tomorrow if it gets delivered before football (unlikely). Otherwise it'll be after work Monday.

07 Boss said:

WTF kinda BS is that? I've never heard of such a thing.

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They just didn't want to do it, so they gave him that BS law.

Update - 10 Months Later
Reverse eventually stopped working altogether.
Shifting from 2nd to 3rd was a little slow and shifting from 3rd to 4th even slower.
After a couple months like that, 3rd gear was totally gone. Would rev really high in 2nd until finally slamming into 4th.
1,2,4 and 5 were fine.
Took to the shop to get a rebuild.
Paid $2800 total and it is running better then it has in years.
All 3 bands were wrecked and the planetary gear. Otherwise no broken parts. Standard tranny rebuild kit.
Got a 12 month 12,000 warranty. Lasted me almost 18 years (116,000+ miles) and this was my first major repair on entire vehicle (well I replaced all shocks/struts, control arms, tie rods, sway bars, calipers, and rotors myself during covid shutdown) so don't think I should have an issue for a while.

Every so often mine hesitates going into reverse. Putting it in park and moving back to reverse always fixes it. I suspect a sensor and/or possibly pump but I did change trans fluid at ~120k and noticed a significant difference in shifting (smoother) used to shift harder - even chirping the tires which truth be known I actually liked. Been running fine otherwise.

ZwookY said:

I haven't noticed a delay shifting from reverse to drive.

I don't know when the fluid was last changed unfortunately. I do know that when I got my last engine oil change they told me they weren't legally allowed to change tranny fluid in Florida if the tranny has over 100K miles (112K) and I'd have to go to the dealer.

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That was not explained properly. It has nothing to do with Florida also. When someone comes in to us for service, if they don't have documentation of the fluid ever being changed prior most times we will not change it either based on higher mileage cars. We don't want to take responsibility for the transmission.

86GT351 said:

That was not explained properly. It has nothing to do with Florida also. When someone comes in to us for service, if they don't have documentation of the fluid ever being changed prior most times we will not change it either based on higher mileage cars. We don't want to take responsibility for the transmission.

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What about engine oil, rear end fluid, power steering fluid, brake fluid, radiator coolant. If people don't bring their "vehicle maintenance log" you don't do any maintenace! hell of a way to run a business.

bambam 06 said:

What about engine oil, rear end fluid, power steering fluid, brake fluid, radiator coolant. If people don't bring their "vehicle maintenance log" you don't do any maintenace! hell of a way to run a business.

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I did not say that. We are discussing Transmission. The general rule of thump in the Auto Industry is if there is no proof of previous service, most shops shy away from it. Sadly many many customers will ask for a Transmission Service when they actually have an internal concern. When that happens and we do the service, now we are responsible for the transmission.

Think of it this way... transmission internals are comprised of friction wear materials. The old fluid although burned, stinky and varnished has a high content of friction material (clutches and bands wearing) so the transmission still performs at an acceptable level.

Drain the transmission of this old fluid and replace with new fluid which does not have any friction material and the transmissions are known to start slip.

Thats why it's better to sometime leave it alone if the service history is unknown.

JC SSP said:

Think of it this way... transmission internals are comprised of friction wear materials. The old fluid although burned, stinky and varnished has a high content of friction material (clutches and bands wearing) so the transmission still performs at an acceptable level.

Drain the transmission of this old fluid and replace with new fluid which does not have any friction material and the transmission are known to start slip.

Thats why it's better to sometime level it alone if the service history is unknown.

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Bingo!

YOU OWE ME A COLD ONE!