4.8 GRX transmission lockup speed

Transmissions, Transfer Boxes, Axles, Drive Shafts
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Re: 4.8 GRX transmission lockup speed

Post by Picasso »

Hi

Can I please ask another laymen's question without high-checking the treat .

Would all the info above also relate to an older 4.5 auto transmission ? :think:

i.e. / quote
Lockup goes on on my Patrol around 105 km and if i slow down and drive at 90km/h (1500 rpm)
do your throttle position learning first as everything is related

For whatever reason there seams to be very little information regarding the 4.5 autobox around

I don't know if it is because there are not many around ? / should not be... ?
Or is it that they do not give any problems ?

Your input is appreciated :salute:
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Re: 4.8 GRX transmission lockup speed

Post by Peter Connan »

I am not entirely sure Henning, but I am under the impression the 4.5 doesn't have a lock-up clutch?
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Re: 4.8 GRX transmission lockup speed

Post by Picasso »

Thanks Peter :salute:

You know... I had the car dyno tuned about 1 1/2 years ago.

the printout (torque / power) showed a spike between 3200 and 3500 rpm which was explained as the torque converter locking up.....

This would mean that it has a lockup clutch ? :think:
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NMAD
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Re: 4.8 GRX transmission lockup speed

Post by NMAD »

It has a lock up function as stated on the work shop manual page 207.

Lock ups between 118-126 km/h and locks off between 114-122 km/h
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Re: 4.8 GRX transmission lockup speed

Post by Clem »

NMAD, you referring to the 4.8?

In any event, that's exactly my issue.
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Re: 4.8 GRX transmission lockup speed

Post by NMAD »

Clem wrote:NMAD, you referring to the 4.8?

In any event, that's exactly my issue.
I am referring to your 4 speed transmission

It has an overdrive switch on the selector handle and depending if this is on or off you won't be able to engage 4th gear or as they call it overdrive 4th gear.

overdrive switch

on-for normal driving push the overdrive switch on
with seletor in drive,the transmission will go into
overdrive as you increase speed

off--for driving up hill and long slopes and going down steep hills
and for driving around town
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Re: 4.8 GRX transmission lockup speed

Post by Clem »

Noel, I'm totally confused. My vehicle (2013 4.8) has a 5 speed transmission and there's certainly no overdrive selector switch. (?)
Picasso
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Re: 4.8 GRX transmission lockup speed

Post by Picasso »

Sorry Clem ... my fault....

further up I pushed in a 4.5 auto question (even so that the treat started of as a 4.8 auto issue)

Peter and Noel were so kind and tried to answer those.

Thanks to both of you Peter and Noel
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NMAD
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Re: 4.8 GRX transmission lockup speed

Post by NMAD »

Clem wrote:Noel, I'm totally confused. My vehicle (2013 4.8) has a 5 speed transmission and there's certainly no overdrive selector switch. (?)
That last lock up spec post for the 4 speed gearbox was for Picasso 4.5 Patrol, sorry mixed you up with him.

The first lock up spec post is your 5 speed box like mine on the 4.8 GRX

Hope that clears it up
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Re: 4.8 GRX transmission lockup speed

Post by NMAD »

NMAD wrote:I am not a mechanic but I see it like this: the auto box has a torque converter and this locks when you are in top gear ie 5th and it almost acts like an extra gear as its lowers the revs more, so if you are cruising at 120km hour in 5th gear at say 2400 rpm and then the transmission locks up the revs will drop lower to say 2200 rpm and you will still go the same speed: it saves fuel but not sure how much.


https://en.wikipedia.org/wiki/Torque_co ... converters

Lock-up torque converters[edit]
As described above, impelling losses within the torque converter reduce efficiency and generate waste heat. In modern automotive applications, this problem is commonly avoided by use of a lock-up clutch that physically links the impeller and turbine, effectively changing the converter into a purely mechanical coupling. The result is no slippage, and virtually no power loss.

The first automotive application of the lock-up principle was Packard's Ultramatic transmission, introduced in 1949, which locked up the converter at cruising speeds, unlocking when the throttle was floored for quick acceleration or as the vehicle slowed down. This feature was also present in some Borg-Warner transmissions produced during the 1950s. It fell out of favor in subsequent years due to its extra complexity and cost. In the late 1970s lock-up clutches started to reappear in response to demands for improved fuel economy, and are now nearly universal in automotive applications.
I was looking through the 4.8 workshop manual and I see that if you put the box gear lever into the manual mode its will go into 4th gear and it can also lock up in 4th gear which will be really good for towing as mentioned in this thread.For the automatic usage the manual says that if you leave it in drive mode it will go up to 5th gear and then lock up with the correct conditions. :thumbup: :salute:
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