OVER DRIVE vs 4 Speed auto

[Razzmaniac]

On my 2007 X (115,000 miles), I normally take the tranny out of OD before I take off. I have driven up to 60 mph or so with it off. The redline is around 6250 and the highest ive ever seen my rpms at out of OD is around 2500. Is there any damage im doing and does it effect the drivetrain at all?
by the way, I only us OD oh highway because of the little extra play the drivetrain causes a clunk in back after I let off he gas a re-accelerate.

 

[Muadeeb]

OD is just another gear, 6th I believe for the G2. The only reason to turn it off would be for towing, as it causes the engine to start to turn less than the output shaft. You are loosing a non-zero amount of mpgs, but then again you are driving a brick. I wouldn't worry about damage running 60@2500.

I'm more concerned with the slap you're hearing/feeling.

 

[Prime]

Turning off OD has absolutely no benefit unless you're towing.

That being said, I seem to remember a big conversation about that driveline slop and clunking. I'd be checking U-Joints, driveshaft, etc. It shouldn't do that.

 

[Razzmaniac]

thanks, going Tuesday for that

 

[TJTJ]

Might be a U-joint for example.

 

[Razzmaniac]

Had the mechanic at the dealer check out the u-joints during the tranny service. He test drove and heard the slap, but said there was no play felt in the driveshaft and the u-joints were fine and wasn't the differential.
Any other suggestions?? Rear axles possibly?

 

[Muadeeb]

Crazy question, and don't freak out, but I noticed you're a 2007... Have you bypassed the tranny cooler in the radiator?

 

[Razzmaniac]

No I have not. I had the radiator replaced last fall though. By a mechanic. What would bypassing it do?

 

[Muadeeb]

There was an issue with the transmission fluid used in the early G2 models, that was fixed around 2008/2009. Basically, the fluid would corrode the cooler in the radiator and cause the fluids to mix. The real fix was to change the transmission fluid to Matic-S. I'M NOT SAYING THIS IS THE ISSUE.

You have an issue where when the OD is not engaged, you get smooth shifting from 1-2-3-4. With OD engaged, you get smooth 1-2-3-4, a slap into 5. What happens after 5th? With the OD engaged, the transmission will then attempt to lock up the torque converter (some may feel this as an additional shift); without it the transmission will stop at 4th. Looking at the FSM, the torque converter should lock up when you're in D3 and D2 as well.

Try this... Put the truck in 3 and count the shifts. If you get 3 RPM drops with no slap, the torque converter locked up fine and the problem is not there. Do the same in OD; if the slap is on the 5th drop, it is when the torque converter lockup engages. If it's on the 4th, there is an issue with shifting into the OD gear.

 

[Razzmaniac]

The slap doesn't come on the shift. It actually happens when I let off the gas to coast then give it gas again. It slaps in the back. Does it only normal Drive. When the tranny has upshifted. If I take the OD off, it wont do it ever. In OD letting off the gas brings the RPMs down when letting off the gas then when given gas, RPMs usually stay down because it was in a higher gear. When OD is off and I let off the gas then give it gas again, RPMs are brought back up because its in the lower gear.

 

[Dmilli0501]

The slap doesn't come on the shift. It actually happens when I let off the gas to coast then give it gas again. It slaps in the back. Does it only normal Drive. When the tranny has upshifted. If I take the OD off, it wont do it ever. In OD letting off the gas brings the RPMs down when letting off the gas then when given gas, RPMs usually stay down because it was in a higher gear. When OD is off and I let off the gas then give it gas again, RPMs are brought back up because its in the lower gear.

I recently purchased an 06 having the same issue. When I drive around with OD engaged, I have no clunking issues as a slow down. If I drive around with OD disengaged, especially in the warmer days, the clunking happens every time I slow down. In addition to that, when I set the cruise around 40-50 mph, it jutters almost like a shift solenoid isn't engaging.

Is there any update to this? I was thinking of draining the transmission fluid and adding some Lucas Transmission Fix along with Valvoline Max ATF...