Correct auto towing procedure

[shack]

I have been wondering what the correct way to use an auto is when towing, ie. at what point you should drop back to third, especially if the car is not running hot and you are able to maintain lockup, is it still a good idea to drop back?

cheers james

[PhilipA]

I think as long as you can maintain lockup there is little to be gained by changing down. By definition that is on relatively light throttle above 80Kmh.

AFAIK most heat is generated in an auto when the Torque converter is slipping and that is under about 2200RPM in an older V8 or 2800 RPM in a TD5.
I always try to keep above those revs if off road and that just about always means low ratio in sand.
I have never had a transmission light on even on sand on a hot day towing my camper trailer.
Regards Philip A

[Blknight.aus]

I'll back phillipA, its near enough..

I'll also add put it in sports when you need to move off or drive it hard up a hill and kick down out of drive when you know your going to have to climb.

[R Miller]

are the discovery torque converters electronic lock up? could a circuit be made to lock them manually?

[Blknight.aus]

d2 yes, d1 no,

yes there are kits that let you override it...

IMHO, leave it alone, its pretty clever for what it is and if you're smart enough to know when you want the torque converter clutch to be locked up then your probably smart enough to be able to drive a manual instead of steering something thats making your driving choices for you.

[Slunnie]

Depends on what you're towing. With light trailers I use D and S mode to stop it from holding gears. With a heavy trailer I use 3 and S except on the open road to minimise labouring and unlocked time which happens between 3rd and 4th locked.

[gavinwibrow]

are the discovery torque converters electronic lock up? could a circuit be made to lock them manually?
The 4speed discovery is a ZF4hp22/24 , We have available a compushift that will control all shift characteristics for the Full Electronic version (ie No TV Cable ).
I am unsure of the year that this changes so you would need to check.
Cost would be around $1700.00 plus fitting

We also have available a lock-up switch for the electronic units that can control lock-up apply in all gears.
Wholesale Automatic Transmissions (http://www.automatictransmission.com.au/release.asp?NewsId=42068)
Cost $ 325 . 00 plus $25 .00 freight

[Pedro_The_Swift]

Gavin,, will this control un-locking?
as in "1st gear less than 40KPH" un-locking?

Shack, is it a rattler or V8?

[gavinwibrow]

Hi Pedro. From reading all the documentation from Wholesale Automatics, I think so, but until I can sort out some wiring issues in my RRC with 1999 D2 TD5 auto ECU (on another thread) and connect the unit up, I can't be 100% sure, especially as I don't know if there actually is a lockup for 1st and 2nd. Plus I have the heavier duty 4HP24. Will post when resolved, but might be a few weeks. Cheers Gavin

[shack]

Its a smooooth diesel :D

[Pinelli]

I think as long as you can maintain lockup there is little to be gained by changing down. By definition that is on relatively light throttle above 80Kmh.

AFAIK most heat is generated in an auto when the Torque converter is slipping and that is under about 2200RPM in an older V8 or 2800 RPM in a TD5.
I always try to keep above those revs if off road and that just about always means low ratio in sand.
I have never had a transmission light on even on sand on a hot day towing my camper trailer.
Regards Philip A

2800rpm?

I'm a bit of an auto novice here, but my TD5 cruises quite comfortably at about 2250rpm at 100km/h. I assumed it has locked at this speed, as it's usually a little higher when I start driving, and drops to 2250 after a few minutes. (I love that it will do this going up a hill as well, almost like clockwork, going home from work each day).

Are you saying its not locked sitting at 2250rpm?

[SiddersC]

It will be locked at 100 kph

You will see/feel it lock at around 80 kph

If towing a decent load, you may find it is lugging a bit at those revs, dropping back to 3rd will get the motor spinning much happier

[PhilipA]

I'm a bit of an auto novice here, but my TD5 cruises quite comfortably at
about 2250rpm at 100km/h. I assumed it has locked at this speed

Yes when you are cruising at over 80Kmh the trans is locked and it locks in 3rd or 4th.
But look at the tacho when you are doing say 70Kmh up a steep hill it will sit on up to 2800rpm, just before the transmission changes down or if you are gentle at say 60 Kmh it will run up to 2800RPM in 4th. That is the Torque converter stall speed ie the torque converter is varying the ratio by "slipping" and it is this slipping which generates heat.
Regards Philip A

[shack]

Just as an interesting side point to heat creation, was very interested to see that my car ran hotter towing in 3rd lockup than it did in 4th lockup at the same speed approx 100kmh,

I'm guessing this would have something to do with the speed the air is going through the small intercooler ,ie not enough time to cool down,as both inlet air temp and engine temp went up, maybe one causing the other.

[d2dave]

If you are towing anything heavy it is also a good idea when moving from stationary to have the auto manually locked in first. This will lock the rear band and take the strain off the one way sprag, which is a known failure point.

[shack]

Do you mean simply moving the gear selector to first to do this or some other means?

[d2dave]

Move gear selector to first. When ready to change to second throw it into drive and then drive it in auto.

If the sprag fails the vehicle will not move unless it is manually locked in first. Theoretically you could manually drive it forever, provided you gave it a very thorough oil change as the failed sprag produces fine metal filling that can jam valves.

I have repaired the odd three speed auto in XF Falcons that have had sprags fail.

A sprag clutch is used in some auto transmissions as a method of allowing the transmission to smoothly change gears under load. Various models of GM gearboxs have used this system.
A sprag clutch is used in most older automatic transmissions and some newer ones for shifts which require the synchronized engagement of one clutch with the disengagement of another. Using an overrunning clutch instead of a hydraulically actuated one makes this synchronization automatic. The sprag clutch simply "lets go" once the reaction force it provides is no longer needed.
In a Simpson gearset, common to many automatics, this happens on the 1-2 shift, and reverses on the 2-1 downshift. The 2-3 shift is done by engaging a single clutch, and nothing is released. Some newer electronically controlled transmissions make "clutch to clutch" shifts, without any sprags.
This can also be used exclusively in first gear (transmission shift lever in D, but auto valve body or management selecting 1st) on some autos. That way it will automatically provide forward drive, but will not provide any engine braking. This is done not so much to avoid engine braking per se, but rather to allow a low throttle opening 2-1 downshift as a car decelerates, to avoid a loud (and potentially abrupt) and unnerving jolt as a result of the downshift. On transmissions so equipped, manual selection of 1st gear typically engages an additional band that grips the same section as the one way clutch would engage, and thus allows for engine braking

By locking the selector in first, this band takes the strain off the sprag

[shack]

Another way to tell whether the trans is locked up is if you take your foot off the throttle the revs will stay up in relation to the speed when locked up.

cheers james

[d2dave]

Another way to tell whether the trans is locked up is if you take your foot off the throttle the revs will stay up in relation to the speed when locked up.

cheers james

This is the method I use. If not locked revs will drop substantially and instantly if you back off the throttle.

[Pedro_The_Swift]

not so instantly here,, I can provoke mine to unlock in 4th and a quick lift off the go pedal isnt met by a quick re-lockup,, its usually quicker to select 3rd and keep going.
yes I know theres a good reason it unlocks,, :angel::angel::angel:

mind you it hasnt unlocked yet with the new motor---:eek: