How Can I Tell If My Automatic Transmission Needs An Overhaul?

How Can I Tell If It's Internal Transmission Damage Requiring An Overhaul?

The biggest give-away, that your vehicle's automatic transmission is kaput and in need of an overhaul or replacement is that it will ‘slip’.

Here are some more specifics that will let you know if it's time for an overhaul or replacement:

1. The transmission fluid level is OK, but it's very dark to black and has a ‘burned out’ smell.
2. Usually (but not always), the PCM will set a ‘gear ratio error’ transmission diagnostic trouble code. Here are some more specifics:
   • P0730: Incorrect Gear Ratio.
   • P0731: Gear 1 Incorrect Ratio.
   • P0732: Gear 2 Incorrect Ratio.
   • P0733: Gear 3 Incorrect Ratio.
   • P0734: Gear 4 Incorrect Ratio.
   A gear ratio error trouble code is the PCM's way of letting you know that it knows the transmission is ‘slipping’.
3. As you accelerate your vehicle, the transmission feels like it was thrown into neutral all of a sudden.
4. No 1st gear. Specifically, you put the transmission in drive but no matter how much you accelerate the engine, your vehicle does not move.
5. The transmission shifts into 1st gear a few seconds after you've come to a complete stop causing a very noticeable jolt (this jolt is more pronounced the faster you've been traveling and the quicker you come to a complete stop). The normal behavior is the transmission shifting into 1st gear before you come to a complete stop.
6. No Reverse gear, although the transmission seems to work fine in Drive.
7. When you remove the transmission oil pan, you find dark sediment. This sediment is the friction material that has fallen off the friction discs (which are located inside the transmission).
8. You may find metal shavings in the fluid pan mixed in with the friction material sediment on the transmission's oil pan.

Removing the transmission oil pan to see if you have metal shavings and/or friction material sediment on the pan is what will give you the definite proof that you have internal transmission damage (and in need of a transmission overhaul).

Transmission With Both Solenoid Failure And Internal Damage

I wanted to make you aware that it's possible for your 4T60-E/4T65-E equipped vehicle to have a failed shift solenoid and internal transmission damage. This is especially true in cases where the internal damage is in the components that create 3rd or 4th gear. What makes the ‘slippage’ (this damage creates) unnoticeable is the simple fact that the transmission doesn't upshift into its higher gears because it's in ‘Limp In Mode’.

From personal experience I have seen cases where the vehicle had a solenoid or transmission sensor issue, along with a specific transmission trouble code and a bad shift solenoid or bad transmission sensor and yet once the failed solenoid/sensor was replaced and the transmission started shifting again, it started to slip in 3rd or 4th gear.

There are a few ways to find out if this is the case in your particular case (like checking for sediment and metal shavings in the pan as you're replacing the shift solenoids) but ultimately it all boils down to replacing the defective solenoid/sensor and road-testing the vehicle.

In Conclusion

Hopefully this article has given you the info you need to be able to say that the issue affecting your automatic transmission is an electrical issue or an internal issue (that requires an overhaul).

If you'd like to share your particular experience with the rest of us (which I'll include in an update to this article), you can use the contact form below: