rezrunner92

I don't think you are dumb either. You are most definitely however uninformed.

Slippage equals friction equals heat.
Lower gear, more torque, more torque converter slippage heat rises faster.
Higher gear at cruising speed, less torque, less torque converter slippage but still slippage so there is heat.
Torque converter locked up, little to no slippage, little to no heat generated.

*edit* The number one enemy of automatic transmissions is heat.

slosurfer

I don't know about the fuel savings, but you aren't losing any fuel savings compared to running with OD off. Like mentioned before, heat is the #1 killer of automatics, you would be amazed how fast the temp cools when OD kicks in. I too, have the 33's with 4.88's so I feel your pain. My OD is constantly kicking on and off, but I can tell you that I appreciate everytime it kicks on and I see my tranny temp take a dive.

Dublin

Thank You rezrunner92 & slosurfer,
This makes it much clearer. Correct me if i'm wrong. Hwy speed vairiable or constant & unlocked TC higher = higher friction & temps. the same with locked TC = lower Friction & temp. Now, what if any effect with 45mph to 65mph and back over & over a short distance on acceleration. I'm thinking longer transmission life and reduced gas mileage. The reason I ask is this is almost a daily route for me.

yota_krazy

rezrunner hit it on the nose. There is no reason not to have overdrive on when highway driving, its just wasting fuel and building heat to not have it on. Just poke the button and your problems will probably disappear. Did they cut and clean your old torque converter when the trans was rebuilt?

rezrunner92

The time you want to have overdrive cancelled is if say you are pulling a trailer. You don't want to use overdrive in a towing situation except when you are cruising and not pulling big hills.

Dublin

New torque converter, that one was a freebee, Seems it got knocked off the bench and they didn't want to chance it. Unlucky them, Lucky me.

Dublin

Still OD off in the city right? Or is there no way that the TC can lock at lower speeds if OD was left on.

rezrunner92

Lucky you indeed, last week I accidentally gave the TC guy one I was supposed to keep as a core. That customer got a new one on me. he didn't need it but hey, new parts is new parts right?

BTW I don't really tell my customers to take it easy when I do an overhaul on a tranny. I tell them to drive it like you stole it, because I know they are probably going to give it heck the next week anyway to make sure I did a good job. Good thing I do.

yota_krazy

you dont need to have the OD on in the city, I would just use it for highway/cruising speeds.

rezrunner92

I think that the tc will apply as long as the switch is not cancelled. IIRC the cancel button prevents lock up. I may be wrong about that one.

slosurfer

I don't think you will have reduced gas mileage, your acceleration from 45-65 is going to be the same as with OD off, because with your gears and tires it won't hold OD for that acceleration. What it will do is once you get to speed OD will kick in and will help your tranny temps at least till the next time it kicks out of OD. I feel for you, I don't like driving mine for short trips on the highway. Mine isn't a DD anymore, otherwise I would have kept my set of 31's that I just sold. I can't wait to regear. I have a 5.29 geared front diff ready to put in, but now I have to find one for the rear.

slosurfer

I have not noticed any difference between OD on or off in the city.

ChickenLover

I leave my OD on all the time. The only time you need to turn OD off is during long/steep highway inclines and when towing.

95RunnerSR5

x2, even though you are shifting into and out of OD in the city, the time spend in OD is helping to cool your tranny. I leave it on all the time except for when towing and have never had a problem.

Dublin

Thanks Guys, You are a great help. The slushboxes have always been an unknown area for me, I grew up with Detroit 70's Muscle spinning syncro's & gears. But when it comes to something that bleeds red it's like "Yikes" that goes for my rig or me.

Dublin

Ok back to revisit this problem, As it turns out I was driving with OD "on". I thought it was like the work truck button in OD on, but on the Yota I pushed the button in and the lite says "OD off". So now what would the problem be, I had been driving the old tranny with over 238,000 for 5 years no problems with the exception a few years ago high temp came on after a 200 mile drive, then went out never to rear it's ugly head again.

rezrunner92

Your torque converter clutch or some other friction element within the unit could be starting to fail. When they start to fail they will slip a little before applying completely. If this is the case you will be looking at a tranny overhaul shortly. Could also be the cooler is restricted. but there wouldn't be any reason for the cooler to be restricted unless the unit is giving off fiber or metal. I would say first off add an external cooler.

Dublin

Wouldn't they have replaced these parts? I know the TC is new, but I would think you could get a bit more than 200 miles on a rebuild. At this rate I'll need to stock up on at least 50 or more rebuilts to make it through the year. I'll check with the shop and get the specifics on what was and wasn't.

slosurfer

What was the reason for getting the rebuilt tranny in the first place?

Dublin

Tranny was slipping badly in all gears.