Torque converter lock up question? - Page 2

**loufish** · 08-14-2006, 10:10 PM

Quote:

in manual 4th gear your TQ converter should not be locking up.

Who told you that? The TC should be able to lock up in 4th

Shane06fl · 08-15-2006, 08:09 PM

Do you feel it lock up when cruising in 4th, you actualy see the rpm's drop off? When your TCQ locks up that is exactly what should happen, it's called Over Drive. In other words the engine Over Drives the transmission. I was wrong when saying the trany and engine spin at the same speed when in OD, I was getting a head of myself.

I don't know about the rest of you but I pull a 4000lb trailer in 4th gear at least once a week and I have yet to have my TQC lock up and drop my RPM's.

If Nissan says it should be locking up in 4th gear manual shift then we can expect premature transmission failures for those of us that pull trailers on a regular basis and I will have to have mine repaired.

QWIKWHIP · 08-16-2006, 06:29 AM

Quote:

Originally Posted by Shane06fl

Do you feel it lock up when cruising in 4th, you actualy see the rpm's drop off? When your TCQ locks up that is exactly what should happen, it's called Over Drive. In other words the engine Over Drives the transmission. I was wrong when saying the trany and engine spin at the same speed when in OD, I was getting a head of myself.

I don't know about the rest of you but I pull a 4000lb trailer in 4th gear at least once a week and I have yet to have my TQC lock up and drop my RPM's.

If Nissan says it should be locking up in 4th gear manual shift then we can expect premature transmission failures for those of us that pull trailers on a regular basis and I will have to have mine repaired.

First of all, the tranny in our trucks DOES lock up in 4th gear, but only when you select 4th gear. If you select 5th gear, it will only lock up in 5th gear. So if you tow with the selector in 4th gear you should defenitly lock up when cruising over 60mph. If your not, there is a problem. Second, overdrive is NOT the act of the transmission locking up. Overdrive is nothing more than the final ratio at the output of the tranny being higher than 1:1. When the tranny goes into lock up, the output of the motor and input of the tranny are turning at the same speed. Also, lock up actually helps prevent tranny failure, not promote it. I'm not sure were you got your info from, but it isn't right.

**loufish** · 08-16-2006, 08:01 PM

Quote:

I don't know about the rest of you but I pull a 4000lb trailer in 4th gear at least once a week and I have yet to have my TQC lock up and drop my RPM's.

Ive only towed twice with about that same weight(maybe a little higher, but no lower) and the above has also been my experience...

QWIKWHIP · 08-17-2006, 06:50 AM

Quote:

Originally Posted by loufish

Ive only towed twice with about that same weight(maybe a little higher, but no lower) and the above has also been my experience...

You should defenitly be locking up in 4th gear. Something isn't right there.

QWIKWHIP · 08-17-2006, 06:56 AM

After digging more in the service manual, it looks to me like our tranny will lock up in what ever gear you select. If you manually select 3rd gear, it will lock up in third gear, etc. So you guys with nonlocking trannies should verify that they are not really locking. It they are not, something is defenitly not right.

Shane06fl · 08-17-2006, 07:44 PM

Wow, not surprised I was wrong but I am surprised the TQC locks up in every gear except 1st. When in D (5th) it only locks up in 5th but In manual it can lock up in all gears except 1st. That is amazing and not the norm. But I have to tell you guys, I never feel it lock up in 4th manual.

Now if the TQC is locking up in 4th and that is the recomended towing gear then why can't we pull in 5th gear. As the old rule in the past, don't pull in OD or 5th gear on a manual trany. I always did and never had a problem and I keep my vehicles well in to the 200,000 mile range. but what is so different about 5th gear in Titan trany that 4th that we shouldn't pull in 5th?

where did you get that data?

I am going to be pulling a 20ft trailer with 5 ATV's this Sunday weighing in at about 5000lbs and a bed full of gear and I will try and feel that sucker lock up.

Qwikwhip back to your original question. Those bigger tires are probably effecting the lock-up points of the TQC. Looking at the chart there is a slip lock up and lock up. You are throwing all that data in the garbage with the bigger tires. There is a formula to get the gear ratio back to stock with the bigger tires. You have to change the gears of course but then you get back the great gas mileage you once had

Shane06fl · 08-17-2006, 08:31 PM

The overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind the transmission unit. It can either couple the input driveshaft directly to the output shaft (or propeller shaft) (1:1), or increase the output speed so that it turns faster than the input shaft (1:1 + n). Thus the output shaft may be "overdriven" relative to the input shaft. It is actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of the clutch.

http://auto.howstuffworks.com/automa...ansmission.htm

Been 15 years since I took the auto trany class I can't remember every detail and technology has evolved since then.

Overdrive
By definition, an overdrive has a faster output speed than input speed. It's a speed increase -- the opposite of a reduction. In this transmission, engaging the overdrive accomplishes two things at once. If you read How Torque Converters Work, you learned about lockup torque converters. In order to improve efficiency, some cars have a mechanism that locks up the torque converter so that the output of the engine goes straight to the transmission.

In this transmission, when overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing. Let's go back to our chart again, this time with the planet carrier for input, the sun gear fixed and the ring gear for output.

Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) = 0.67:1
So the output spins once for every two-thirds of a rotation of the engine. If the engine is turning at 2000 rotations per minute (RPM), the output speed is 3000 RPM. This allows cars to drive at freeway speed while the engine speed stays nice and slow.

Yes I worded it wrong, my fualt. But that is what I was getting at. The engine is spinning at 1/3 the RMP as the output of the trany when OD is used.

That gets me to thinking. With the new transmissions going to these higher range of gears 1-5 and 1-7 like the Lexas do they even use a OD set up or do they end it at 1:1 ratio? If it ends at 1:1 then the Titan should be able to pull in 5th gear depending on the load without damaging the transmission.

I am still learning all the tricks this truck has. I just learned the other day that if I hold the unlock button down the windows roll down and the doors lock and set the alarm.

**loufish** · 08-17-2006, 11:27 PM

Quote:

Now if the TQC is locking up in 4th and that is the recomended towing gear then why can't we pull in 5th gear. As the old rule in the past, don't pull in OD or 5th gear on a manual trany. I always did and never had a problem and I keep my vehicles well in to the 200,000 mile range. but what is so different about 5th gear in Titan trany that 4th that we shouldn't pull in 5th?

Almost every manufacture recomends NOT towing in overdrive, unless it's a very light load. For the Titans that means staying out of 5th. When you tow in OD, it's a very tall gear, and with a planetary gear set such as used in modern automatic transmissions, one portion of that gear set has to be held from rotating, there by forceing the other part of the gear to rotate at the set OD speed.
Now, the more torque applied to the trans which comes from towing heavy loads, or pulling up-hill, the more load is applied to the part of the gear set we want to stay stationary, so the clutches the keep the part from turning can over time start to slip when that much torque is applied.
The slippage can slowly increase while towing in OD so that you never feel it, right up to the point that the trans starts to act funny...
Of course by towing in forth, it still has a part of the gear set that has to be held from spinning, but because 4th has a lower gear ratio it's easier to keep that part from spinning and that's why you don't tow in OD...

gyrate · 08-18-2006, 01:47 AM

not related to towing, but mine locks up at random. i am still to figure out what criteria it uses to do it. the older nissans simply used speed/engine load and no matter what they would lock it. this one, like the infiniti has a mind of its own.

QWIKWHIP · 08-18-2006, 08:16 AM

Quote:

Originally Posted by Shane06fl

Wow, not surprised I was wrong but I am surprised the TQC locks up in every gear except 1st. When in D (5th) it only locks up in 5th but In manual it can lock up in all gears except 1st. That is amazing and not the norm. But I have to tell you guys, I never feel it lock up in 4th manual.

Now if the TQC is locking up in 4th and that is the recomended towing gear then why can't we pull in 5th gear. As the old rule in the past, don't pull in OD or 5th gear on a manual trany. I always did and never had a problem and I keep my vehicles well in to the 200,000 mile range. but what is so different about 5th gear in Titan trany that 4th that we shouldn't pull in 5th?

where did you get that data?

I am going to be pulling a 20ft trailer with 5 ATV's this Sunday weighing in at about 5000lbs and a bed full of gear and I will try and feel that sucker lock up.

Qwikwhip back to your original question. Those bigger tires are probably effecting the lock-up points of the TQC. Looking at the chart there is a slip lock up and lock up. You are throwing all that data in the garbage with the bigger tires. There is a formula to get the gear ratio back to stock with the bigger tires. You have to change the gears of course but then you get back the great gas mileage you once had

That data is from the 04 service manual. As far as towing in fifth, loufish explained that pretty well. In simple terms, the higher the gear, the more stress the drivetrain sees.

As for my tires, I agree that the bigger tires are playing a bit of havock with the computer and shift points. But until someone comes out with gears and some programing to help fix it, I as well as many others are stuck.

There are five sensors the ecu is reading to get it's info from. The wheel hub sensors (four of them) and there is an internal tranny shaft speed sensor. So they are now seeing diferent speeds with the larger tires. This is similar to the issue RB'sTitan is having after he put the 3.36 BT gears in his non BT truck. They just make these things too damn complex these days. lol

Shane06fl · 08-18-2006, 06:22 PM

I would like to do some mods to my truck mainly for better pulling and lowend a$$ kicking power, not that these trucks don't have plenty and I can tell you first hand from pulling with every type of 3/4 ton truck made these Titans will come very close to being equal. But I don't see a lot of aftermarket support. It's too bad too. I know there are ways to get the TQ over 400pound feet but at low end but all the aftermarket stuff is all top end high RPM add on's. I haven't looked for lower gearing and really don't think for that is the cure all but I am sure you can get a gear set up that will come close to bringing back to stock.