Efficiency on the motorway

[da SLUG man]

The gearbox used to lock at 50 MPH but seems to lock at 48 MPH since I fitted 31" tyres.

surely it would read the same as before?

the only thing that's changed is that the tyres make you travel further at 48mph(indicated)... the gearbox is doing exactly the same speed now at 50mph as before?



um.... i think i've just confuded myself.... just gonna have to draw a picture!

[dave95979]

my 91 2.4 that i am selling did 31 mpg from ipswich to winchester cost
21 quid to do it oll though that was with a verry light foot !!

[kitesurf_phil]

surely it would read the same as before?

the only thing that's changed is that the tyres make you travel further at 48mph(indicated)... the gearbox is doing exactly the same speed now at 50mph as before?



um.... i think i've just confuded myself.... just gonna have to draw a picture!

That was the point of mentioning it. It just doesn't make sense.

[dirtydog]

Gearbox oil condition does have an effect on the revs for a given speed in any auto. Check condition of oil and level. If its ever been burned or seriously overheated it looses efficiency and so the engine will have to produce more revs to get to the same speed as a simillar car with an auto box in tip top order.

Al.

it towed lots so i changed it a few months back and didnt make a difference really, i thouht the same as you though. havent really towed since.

[dirtydog]

just out of interest i can get my box to lock up at 35mph if im clever.
something is way off here if you can't get yours to go until almost 50!

[Slugger]

just out of interest i can get my box to lock up at 35mph if im clever.
something is way off here if you can't get yours to go until almost 50!#

What is meant by gearbox locking off ? , as you can probably tell , i am not that familiar with this mechanical lingo !

[dirtydog]

its when the gearbox drops into top gear

[andy]

its when the gearbox drops into top gear

It will already be in top gear at around 40mph, the lock up is explained more here.

http://dnr.louisiana.gov/sec/execdiv...p/auto/f/f.htm

[Bludger]

I'm thinking of getting a Hilux Surf (2.4 1991) but I do a lot of motorway driving. How efficient do you think it would be on a long run?

Fill it with Vege !!

. . . Fill it with Vege !!

. . . . . . Fill it with Vege !!

Makes the cost fuel 'Cheap as . . . well . . . Chips!'

[Slugger]

its when the gearbox drops into top gear

Thanks M8 , will check in morning after me night shift !!

[dirtydog]

It will already be in top gear at around 40mph, the lock up is explained more here.

http://dnr.louisiana.gov/sec/execdiv...p/auto/f/f.htm

anyone notice a pattern here... i defo dont get any other drop in revs after 40mph and my truck eats fuel!

thanks for the link!

[kitesurf_phil]

anyone notice a pattern here... i defo dont get any other drop in revs after 40mph and my truck eats fuel!

thanks for the link!

That is what i have been trying to get across for a year since several people said that their 70 MPH was at 3000 RPM or more. The lockup is very noticable, especially if it locks when you are on the slip road getting up to motorway speed, when the revs suddenly die back. That is why, when I am about to join the motorway or I am about to overtake, I flick the overdrive off.

[dirtydog]

well mine will change at 50-60 if im on the power and i know the feeling!
a roundabout near me on the A406 goes up the slip road and keeps going up for about 1/2 mile. revs dies off at 50 odd and your stuck with no power!

just keep your foot down!

you saying your revs are much lower than that phil? im sure i can get mine to lockup just below 40. want to come try mine?

[Diezel Weazel]

Over the last week or so bi running up to N/Lincs & back twice in all, both times round trips 450 kms x 40 litres @ 65-75 mph = nearly 30ish.

[slim]

it all depends on your final drive ratio, I thought i had a problem with the torque converter not loading up some time ago because i was doing 60 mph @3000 rpm high i thought!!! well having done research i did find out that this was correct,then i had a problem with the rear diff so bought a set of diffs from tonyn the original ones were 4.8 the new ones are 4.3. now at 67 mph is 3000rpm not a lot of diffrence but i suppose to make a real diffrence the box would also need changing too. research your final drive ratio and see wot u come up with....