O/D while driving
- Thread starter NKlekas
- Start date
That is what the switch is for. But instead of making fun, I just googled it. Found this right off from this sight, from @AjRagno.
Overdrive off = torque converter clutch lockup in 3rd gear with 1:1 ratio
Overdrive on = torque converter clutch lockup in 4th gear (overdrive) with 0.69:1 ratio.
Though the gearing in overdrive is not great, it’s the TCC lockup that reduces the RPMs and effectively makes overdrive useless in many situations.
It’s not as simple as keeping overdrive off at all times because now the PCM is going to lockup the TCC too soon in 3rd. Instead, learn what gear you’re in and when the TCC is locked up.
With 3.73 gears and 31” tires, keep overdrive ON from 0-40 MPH and overdrive OFF 40-60 MPH. If you come to a hill in overdrive and the engine lugs, rather than forcing a downshift, keep steady throttle and turn overdrive off. This will unlock the TCC, downshift from 4th to 3rd, the TCC will lockup again in 3rd with a 1:1 ratio and you’ll have plenty of pulling power while also keeping the heat down.
The only real control you have with this transmission is the overdrive on/off switch. It does nothing more than control whether you will shift into 4th and which gear TCC lockup occurs.
Overdrive off = torque converter clutch lockup in 3rd gear with 1:1 ratio
Overdrive on = torque converter clutch lockup in 4th gear (overdrive) with 0.69:1 ratio.
Though the gearing in overdrive is not great, it’s the TCC lockup that reduces the RPMs and effectively makes overdrive useless in many situations.
It’s not as simple as keeping overdrive off at all times because now the PCM is going to lockup the TCC too soon in 3rd. Instead, learn what gear you’re in and when the TCC is locked up.
With 3.73 gears and 31” tires, keep overdrive ON from 0-40 MPH and overdrive OFF 40-60 MPH. If you come to a hill in overdrive and the engine lugs, rather than forcing a downshift, keep steady throttle and turn overdrive off. This will unlock the TCC, downshift from 4th to 3rd, the TCC will lockup again in 3rd with a 1:1 ratio and you’ll have plenty of pulling power while also keeping the heat down.
The only real control you have with this transmission is the overdrive on/off switch. It does nothing more than control whether you will shift into 4th and which gear TCC lockup occurs.
You also have the ability to control if it shifts out of 2nd or 1st gears.
Press it anytime without issue. It's not just O/D like @Kid Mechanic says, it changes the entire shift program to reduce heat generated by the transmission for towing. Early torque converter lockup, late shits and much less partial lockup of the torque converter. The heat reduction is why Jeep recommends towing only with the O/D off. It isn't just about overdrive, it's an entirely different shift program.
If you have larger tires than stock, the OD really isn't that good. I only use it on the freeway after I've reached the speed I want. Get up to 65+, then turn it on.