The gearbox was changed in the lorry

[BethanT]

A while ago I posted about the speed of which my lorry was going, and that it couldn't get over 45mph on the flat.

Well it has been looked over by a mechanic and he said that the gear box has previously been changed, which means that it is running in low gears!

I am yet to speak to the Mechanic to find out how big of a job it would be for it to be altered back, or any indication as to why it would have been changed in the first place, but does anyone have any experience of this?

Lorry is 2002 Ford Iveco, and does actually have 6 gears......

 

[Gingerwitch]

what weight box is it ?

 

[BethanT]

Sorry, 7.5ton

 

[Gingerwitch]

It could be the wrong box for the diff was fitted, or it could be that the vehicle has been "limited" to that speed for some reason or another.

 

[BethanT]

It could be the wrong box for the diff was fitted, or it could be that the vehicle has been "limited" to that speed for some reason or another.

It has a rev limited on it due to its age. But Mechanic said that the speed being limited to 45mph is down to the fact the whole gearbox was changed at some point.

Just wanted to know approx costs of getting a proper gear box as can't find anything on google!

 

[Bob notacob]

what you need to change is your mechanic, or rather replace this non mechanic with someone who realises that in top gear , the propshaft turns at engine speed . This is prettywell universal,short of having overdrive. Changing the gearbox wont change the top speed.Far more likely is that the back axle has been changed. My appologies to your "mechanic"if I am wrong but I think it highly unlikely that a six speed 2002 ford Iveco 7.5 tonner has overdrive (ie the prop turns faster than the engine in the highest gear)if only for the fact that it would drink fuel like it was going out of fashion.

 

[popsdosh]

what you need to change is your mechanic, or rather replace this non mechanic with someone who realises that in top gear , the propshaft turns at engine speed . This is prettywell universal,short of having overdrive. Changing the gearbox wont change the top speed.Far more likely is that the back axle has been changed. My appologies to your "mechanic"if I am wrong but I think it highly unlikely that a six speed 2002 ford Iveco 7.5 tonner has overdrive (ie the prop turns faster than the engine in the highest gear)if only for the fact that it would drink fuel like it was going out of fashion.

Indeed Iveco did have a lower geared version of gearbox that went into ECs for town work deliveries and it is something you should check out when buying one. Many were caught out by this. OP when you say 45 are we talking MPH or KPH and what is the Rev counter reading at that speed . Is it also maybe on smaller wheels? Do you have the tyre size?
Bob Nac I think you got mixed up with your description of overdrive as surely they would save fuel and give a higher speed at lower revs . If my memory serves me well the normal 6 speed box for long distance work has 5 th as direct drive and 6th is an overdrive gear.
OP the only way to truly tell is to check out the ratios fitted to gearbox and Diff . If you can get the info off the ID plates on both I can help as I have the workshop manual somewhere here on a CD and can check out the ratios.

SH gearbox will be about £600 or rear axle a bit less. You can change the diff ratios on a euro cargo without removing the whole axle but you need to know what your up to.

 

[popsdosh]

Just had a quick check and indeed the six speed box does have over drive so most likely it is the rear axle diff ratio there are 8 options running from 3.15:1 to 5.5:1 so a huge range .

 

[turnbuckle]

popsdosh has it spot on.

Probably the original box broke and they put one from a breakers in without checking ratios.

Or could be the final drive ditto.

In any case, one or t'other will need swapping, hopefully popsdosh's CD will help or you need to get a Ford dealer (for love not money) to do some digging on specs and make sure whatever you swap in has the right ratios.

Where in the country are you?

 

[turnbuckle]

Just thinking over, I would go with the final drive too, which is good. Very quick to pull out, check number of teeth and make sure new (s/h) one has right number of teeth. And there are still plenty around in breakers yards.

 

[Bob notacob]

Yes ,even if 6th is an overdrive,you should still be able to go at least 45 in 5th which would be straight through ,so the problem is with the diff gear ratio .The easiest way to check the ratio is to chock the front wheels , jack up one rear wheel ,mark the tyre and propshaft , handbrake off .Turn the propshaft by hand counting the number of turns till the wheel has made a complete revolution.Then divide this number by 2 .So for example if it takes 14 revolutions of the prop shaft to turn the wheel 1 turn ,the ratio is 7 to 1 . Much easier than trying to calculate the ratio by counting teeth (remembering of course that both the crown wheel and pinion would need to be counted.)

 

[turnbuckle]

Cool trick! Thanks!

 

[Keith_Beef]

jack up one rear wheel ,mark the tyre and propshaft , handbrake off .Turn the propshaft by hand counting the number of turns till the wheel has made a complete revolution.

I've not tried doing that, but it seems to me that it would be easier to turn the wheel by hand.

You'd be standing next to the wheel, rather than laying under the lorry trying to turn the propshaft, so you would be able to use your leg muscles, not just your arms, and I think it would be easier to get a bar on the lug nuts, rather than get some grip on the propshaft.

It also seems to be a job for two people, one laying under the vehicle counting the turns of the prop shaft, one by the wheel, counting its turns.

I'd also be wary of working alone with a vehicle up on axle stands...

 

[Bob notacob]

Its not like you are taking the wheel off . The wheel just needs to be just clear of the ground. Also the other wheel is still on the ground . Yes it helps to have a second person ,though you can mark the inside of the tyre and do it yourself. Turning the wheel and counting revolutions of the prop is going to be far harder particularly if the box has skirts.

 

[Keith_Beef]

Its not like you are taking the wheel off . The wheel just needs to be just clear of the ground. Also the other wheel is still on the ground . Yes it helps to have a second person ,though you can mark the inside of the tyre and do it yourself. Turning the wheel and counting revolutions of the prop is going to be far harder particularly if the box has skirts.

Like I mentioned, it's not something I've tried, so I may well be wrong in what I'm imagining. I noticed that you didn't mention removing the wheel, but you did mention jacking it up...

I suppose that under a vehicle of that size, there's enough clearance to lie underneath it even without jacking it up or putting it on axle stands (I remember hiding under buses and lorries as a kid).

Maybe another way to do the counting is to put a cheap camera and a battery powered lamp under the lorry. You set things up, set the camera going, wait for ten second, then start turning for the number of turns you need for the calculation, then afterwards you watch the video and you'll see after the pause that the other component starts turning and there you start to count the turns.

 

[OldFogie]

One thing I'd ask is - has your lorry always behaved like this or is the 45mph a new thing? With the lorry out of gear and standing still - what revs will the engine do? (Don't over do it!)

All Fords have an electronic engine management limiter designed to prevent you inadvertantly damaging the engine by driving too fast in certain circumstances such as low oil pressure - they have been know to go into fault mode without the symptoms being present. Guess what speed it limits you to?

 

[DabDab]

Hehe, this thread is why my job drives me nuts at times - any mechanical issue and every man in the vicinity rocks up to give an opinion, many of them saying exactly the same thing in a slightly different way and managing to disagree about it....

Bob, pops and tb - I'm pretty sure you are all saying exactly the same thing, coming at it from different directions

KB - Bob said to Jack it up to turn the wheel because how else would you turn it

OF - I have no idea what the limp mode limits an iveco EC to but I would be surprised if it's more than about 20mph

Sorry OP, no answer to your question, did the mechanic offer you a quote? Probably worth taking it to someone else for a look

 

[popsdosh]

Hehe, this thread is why my job drives me nuts at times - any mechanical issue and every man in the vicinity rocks up to give an opinion, many of them saying exactly the same thing in a slightly different way and managing to disagree about it....

Bob, pops and tb - I'm pretty sure you are all saying exactly the same thing, coming at it from different directions

KB - Bob said to Jack it up to turn the wheel because how else would you turn it

OF - I have no idea what the limp mode limits an iveco EC to but I would be surprised if it's more than about 20mph

Sorry OP, no answer to your question, did the mechanic offer you a quote? Probably worth taking it to someone else for a look

Yes well I thought I would let them get on with it . The easy way is to read the id label on the axle as they very rarely come off .the ratio will be marked on the axle. Alternatively assuming the axle is the original it should be on the vehicle data plate next to box that says rear axle.
As I say if its six speed gearbox theres eight different diff ratios that could be fitted a five speed has seven options.
It takes about an hour to swap the diff ratios with the axle in situ. Not a job for the inexperienced though as backlash in the gears is critical to get right but you dont need special tools. Did it on the hard shoulder of a motorway once to get a friends horse box moving when they stripped the diff.
OP if you have a competent mechanic I could email the info over so they have the methods.

OP the model number is the most helpful thing at this stage which gives away most of the build spec .This is on the plate at the front of the driving position when you lift the front cover as if checking the oil level. Sadly this will not give the ratio but would narrow down the gearbox and rear axle numbers. It will start ML

 

[Bob notacob]

Sure but you make the assumption that the ID label os still there after 16 years and that no one has changed the diff within the axle.