Where is located the transmission ground strap

The strap with 3 ends....connect it to the frame. You can strap the alternator to the block.

The alternator is grounded to the engine block. The lights and most of the accessories are grounded to the chassis. Since the engine and transmission are mounted on rubber shock mounts, they are isolated from the chassis. What is probably happening is that because you have no solid ground bonding strap from the engine block to the chassis, ground is being made thru some other, high-resistance path, such as , say a transmission cable linkage that connects from the column/floor shifter to the transmission. This causes a voltage drop and reduces voltage to the electrical items. This problem will eventually damage the voltage regulator and alternator as it must work harder to maintain proper output. Get a bonding strap from a bare metal point on the engine block to a bare metal point on the firewall ASAP.

I doubt that it would.
The engine and transmission are bolted together, and the battery is grounded to the engine and the body. So if it will crank, the engine would be grounded to the battery, and therefore also the transmission.

Transmission bolt on passenger side by starter

ground straps on engines are either from the battery earth post to the engine or to a body point . If it is to a body earth point the engine earth strap will be around an engine mount. From the engine bolt around the rubber to the body mount bolt. probably on the mount closest to the battery

When you go to an auto store and they give sell you spark plugs they should already be gapped to spec. There is no need to adjust the gap. This may be the reason your car will not start. I would try new spark plugs first then wires. Since the vehicle is a 99 it probably could use a tune up (spark plugs, wires, coils, cap, rotor, chassis lube, and transmission fluid check and flush if needed). Also make sure that the engine block ground strap is in good condition and that there is no corrosion covering the ends of the ground strap. The ground strap is typically located near the firewall and is directly attached from the engine block to the frame of the car.

That is a pretty robust transmission but its computer is very sensitive the quality of the electrical supply. If you take it to a shop, they will probably put a known good battery in the car and check and clean the electrical grounds before they even look at the transmission. If this is your original battery, you will probably save yourself some money (and perhaps a trip to the transmission shop) if you replace the battery yourself and clean any ground connections you can find. Sorry, but other than the one near the battery, I am not familiar with the ground locations on this model, though there should be a ground strap around one of the engine mounts that should be inspected/cleaned.

The transmission solenoids are not working properly. Probably requires a transmission rebuild.
I don't think it's in the ground strap or wiring.
It's an internal problem with the transmission.

the ground strap is bolted to the transmission housing next to the starter bolt.the transmission not shifting may be caused by the computer and may need to be reprogrammed for the new transmission.

1. Remove or disconnect the following:
   • Negative battery cable
2. Raise the vehicle and support the fuel tank with a transmission jack.
   • Fuel line from the front of the tank
   • Ground strap
   • Inboard side of the fuel tank straps and front T strap fastener and lower the tank about 6 inches
   • Fuel lines from the fuel pump module
   • Fuel filter
3. Installation is the reverse of removal. Tighten the fuel filter bolts to 40 inch lbs. (4.5 Nm), the main tank straps to 40 ft. lbs. (54 Nm) and the T strap to 250 inch lbs. (28 Nm).
4. Start the engine and check for leaks.