Upshift 3 to 4 on V8 auto - Page 4

kaiser · 16th January 2012, 15:22

I have occasionally felt that as well./ I don't know if it is particularly from 3rd to 4th, but it is as if there is a momentary lack of power.
I think it has to do with the traction control somehow, which cuts engine power in certain conditions. I wrote to a company, which is inolved in the control. I will see if I can find the e-mail:

I wrote to them because my traction control light would come on for no good reason, and the my speed control would not function.
Before you all start writing, I think I have found the reason for that. I put two new front tyres on, original spec I think 225/50 and I have two rear tyres 235/45 (from memory!) the running circumference is big enough for the ABS sensors to register different speeds for the individual tyres. Normally that would be the precursor for a skid, and that would register on the traction control. I think that is the reason, as my incidents have become less frequent with time (as the front tyres are wearing a bit, I think)

Anyway here is the one e-mail: I have removed the name and the costs, and I hope this will be used in good spirit!

Hi Mr Kaiser,

To be frank this is going to be just about impossible to diagnose but I'll give it a go...

First some background: the xxxxxx unit constantly reads wheel speeds and at the point that wheel spin is occurring it feeds the information, including how much spin is happening and therefore how much power needs to be reduced, into the car's CAN system via an SCP gateway. The car's processing then takes the info and calls for a reduction in torque which is achieved via timing retardation.

So this version of our after-market traction control product is a bit different, and integrates with the car's systems that had nothing to do with us... Rover wanted it this way because they didn't like the idea of our box controlling the injectors, which is the way the unit normally works.

So the problem could lie in any number of places: you might have an ABS sensor going faulty; there could be a issue with the xxxxx control module; or it could be the car's ECU.

The only possible solution that I can come up with is to sell you a new control module to see if this fixes the issue but I must say I think it's very unlikely: they're incredibly reliable.

Let me know what you'd like to do.

J1MBO · 17th January 2012, 10:40

Kaiser that makes interesting reading and yes as you've found out both the abs and traction systems don't like different size tyres on front and back. A fact a friend found out with a 260 he bought fitted with 19" rims and wider tyres on the rear, this has now been solved by fitting 18" with the same width all round.

Never had any issues myself other than the traction kicking in when flooring the loud pedal from a standing start

J1MBO · 18th January 2012, 11:21

Quote:

Originally Posted by kaiser

The box on the smaller Rovers have a lock-up function, which effectively mechanically couples the input and output shafts, eliminating the losses in the torque converter in top gear.
When that engages, you get a drop of a few hundred rpm as the shafts lock solidly. That feels like an extra gear, but is just the torque converter slip taken up.
I am not even sure if our boxes have such a function. I seem to remember having read they do, but I am not sure I have ever noticed it engage.
Must try and find out.

Just a bit of lateral thinking - as the 4R70W auto box 4th gear is described as an overdrive ratio I wonder if as it changes into 4th maybe the torque converter is also locking up, hence the delay or "slur" in engaging it.

75SCO · 18th January 2012, 11:53

That's what I was wondering, and had hoped somebody on here knew. Didn't even know the thing was called a 4R70W but now I do. Will google it and see if other owners in other cars have something to say about it. Thanks.

J1MBO · 27th January 2012, 13:09

Quote:

Originally Posted by J1MBO

Mine does not want to go into top gear until at least 35/40 mph and only if the throttle pedal is lifted. As you say it does seem to take some time to change gear and at those speeds any pressure on the pedal will bring about an immediate change down.

I'm still amazed I've not been noticing at least one of the transmissions changes, I guess it must be my driving style and as I lift off it's changing up 2 gears. I'll have to check this out.

Not been using the V8 much this month so couldn't give any feedback regarding the autobox changes.

It's as I thought:

When on light throttle I've not noticed the 1st to 2nd change as it's virtually impossible to discern it - only noticable by watching the rev counter and seeing a slight dip in the revs as the change is made.

When on heavy throttle from a standing start the box is holding onto a lower gear and then changing up two gears, ie: 0-70mph under heavy throttle, the change from 1st to 2nd is felt then it holds 2nd until you lift off when it goes straight up to top.

Ho hum, wonder what else I've not noticed.

kaiser · 27th January 2012, 13:42

Quote:

Originally Posted by J1MBO

Not been using the V8 much this month so couldn't give any feedback regarding the autobox changes.

It's as I thought:

When o......................s made.

When on heavy throttle from a standing start the box is holding onto a lower gear and then changing up two gears, ie: 0-70mph under heavy throttle, the change from 1st to 2nd is felt then it holds 2nd until you lift off when it goes straight up to top.

Ho hum, wonder what else I've not noticed.

No, that's just because you loose the nerve when the fun starts.

Close your eyes a bit, and press the pedal to the metal, and you will see shift into 3, then into 4, quite progressively.
Go out and try, if you dare!!

J1MBO · 27th January 2012, 14:37

Quote:

Originally Posted by kaiser

No, that's just because you loose the nerve when the fun starts.

Close your eyes a bit, and press the pedal to the metal, and you will see shift into 3, then into 4, quite progressively.
Go out and try, if you dare!!

Wish I could, just checking what the op had originally asked for on the "full of camera's" local bypass whilst I was seeing if I could feel the gearchange I seemed to be missing.

A year or so ago at Bruntingthorpe had it up at 130+ from a standing start - nice, hope to be able to do it again later this year

kaiser · 27th January 2012, 15:07

I see. Thought your one slipper got caught under the loud pedal

()

16th January 2012, 15:22	#31
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	I have occasionally felt that as well./ I don't know if it is particularly from 3rd to 4th, but it is as if there is a momentary lack of power. I think it has to do with the traction control somehow, which cuts engine power in certain conditions. I wrote to a company, which is inolved in the control. I will see if I can find the e-mail: I wrote to them because my traction control light would come on for no good reason, and the my speed control would not function. Before you all start writing, I think I have found the reason for that. I put two new front tyres on, original spec I think 225/50 and I have two rear tyres 235/45 (from memory!) the running circumference is big enough for the ABS sensors to register different speeds for the individual tyres. Normally that would be the precursor for a skid, and that would register on the traction control. I think that is the reason, as my incidents have become less frequent with time (as the front tyres are wearing a bit, I think) Anyway here is the one e-mail: I have removed the name and the costs, and I hope this will be used in good spirit! Hi Mr Kaiser, To be frank this is going to be just about impossible to diagnose but I'll give it a go... First some background: the xxxxxx unit constantly reads wheel speeds and at the point that wheel spin is occurring it feeds the information, including how much spin is happening and therefore how much power needs to be reduced, into the car's CAN system via an SCP gateway. The car's processing then takes the info and calls for a reduction in torque which is achieved via timing retardation. So this version of our after-market traction control product is a bit different, and integrates with the car's systems that had nothing to do with us... Rover wanted it this way because they didn't like the idea of our box controlling the injectors, which is the way the unit normally works. So the problem could lie in any number of places: you might have an ABS sensor going faulty; there could be a issue with the xxxxx control module; or it could be the car's ECU. The only possible solution that I can come up with is to sell you a new control module to see if this fixes the issue but I must say I think it's very unlikely: they're incredibly reliable. Let me know what you'd like to do. Last edited by kaiser; 16th January 2012 at 16:21..

18th January 2012, 11:53	#34
75SCO Regular poster Jaguar X-Type Estate Join Date: Nov 2011 Location: Scottish Highlands Posts: 97 Thanks: 0 Thanked 1 Time in 1 Post	That's... That's what I was wondering, and had hoped somebody on here knew. Didn't even know the thing was called a 4R70W but now I do. Will google it and see if other owners in other cars have something to say about it. Thanks. __________________ Six-thirty-one sold

27th January 2012, 15:07	#38
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	I see. Thought your one slipper got caught under the loud pedal () Last edited by kaiser; 27th January 2012 at 15:09..

17th January 2012, 10:40	#32
J1MBO This is my second home Roverless & now carless Join Date: Dec 2008 Location: Wilmslow Posts: 15,583 Thanks: 2,457 Thanked 2,428 Times in 1,301 Posts	Kaiser that makes interesting reading and yes as you've found out both the abs and traction systems don't like different size tyres on front and back. A fact a friend found out with a 260 he bought fitted with 19" rims and wider tyres on the rear, this has now been solved by fitting 18" with the same width all round. Never had any issues myself other than the traction kicking in when flooring the loud pedal from a standing start