The Subaru SVX World Network   SVX Network Forums
Live Chat!
SVX or Subaru Links
Old Lockers
Photo Post
How-To Documents
Message Archive
SVX Shop Search
IRC users:

Go Back   The Subaru SVX World Network > SVX Main Forums > Technical Q & A

Reply
 
Thread Tools Display Modes
  #16  
Old 10-05-2005, 03:20 PM
pavanbabut's Avatar
pavanbabut pavanbabut is offline
Registered User
 
Join Date: Jul 2004
Location: Fremont. CA
Posts: 1,269
Send a message via MSN to pavanbabut Send a message via Yahoo to pavanbabut
Quote:
Originally Posted by lee
Could someone explain how this error could happen by a swap?

My understanding of the speedo setup is that a gear is driven from the right side axle, which in turn does some magnetic signaling that gets decoded and sent on to the speedometer.

My point is the speedo, since it's driven by axle revolutions, should register exactly the same (good or bad) before & after, regardless of the ratio installed.

So, which automotive class do I need to take over again?
same here toooo... not able to understand... maybe Tom[svxfiles] can explain this clearly as he is the master in swaps 4.11 and 4.44.

-Pavan.
Reply With Quote
  #17  
Old 10-05-2005, 07:33 PM
joeaxial joeaxial is offline
Registered User
 
Join Date: Aug 2005
Location: Wales, ND
Posts: 40
Quote:
Originally Posted by lee
Could someone explain how this error could happen by a swap?

My understanding of the speedo setup is that a gear is driven from the right side axle, which in turn does some magnetic signaling that gets decoded and sent on to the speedometer.

My point is the speedo, since it's driven by axle revolutions, should register exactly the same (good or bad) before & after, regardless of the ratio installed.
You got me thinking on this 'cause on a typical Front engine/rear drive car, the speed sensor senses transmission rotations and is independent of the final drive ratio. I did some research and found a copy of a tech document concerning our 4eat transmissions published by Subaru at this site http://www.ravensblade-impreza.com/t...ssion/4eat.pdf I'm now quoting from this document:

Vehicle Speed Sensor #1
Vehicle speed sensor #1 is mounted to the transmission and is basically electrical governor pressure. It is used to detect vehicle speed and it effects shift points, lock-up, and line pressure. In FWD transmissions the speed sensor reads parking gear rotation at the front output shaft. In AWD transmissions it senses the transfer clutch drum rotation at the rear output shaft.

Vehicle Speed Sensor #2
Vehicle speed sensor #2 is built into the combination meter. In FWD units, it is used as a back-up for speed sensor #1. In AWD units, it is used as the front output shaft speed sensor.


If I'm reading this doc correctly, #1 takes a reading from the rear output shaft while #2 takes a reading from the front output shaft before the front differential. I took a look at the wiring diagram for my 1992 SVX and it shows that the speedometer is driven by Vehicle Speed Sensor #2. Neither speed sensor would be affected by final drive ratio, so speedometer readings would naturally be inacurate after changing the final drive ratios.

I emailed the tech guy at http://www.terf.com/SpeedChangerPage.htm. He indicated that the SpeedChanger box would work with the Subaru electrical system, but I'm concerned that if it wasn't wired into the correct spot on the harness it could cause the TCU to think that the front wheels would be turning at a different speed than the rear and cause a whole pile of problems.

Any Thoughts?
Steve
__________________
1992 SVX lsl - >111K, pearl, 4.44 gears, ECUtune stage 1
2005 Outback XT wagon - i love that turbo!!!!
2004 Dodge Ram 1500 Hemi
Reply With Quote
  #18  
Old 10-05-2005, 07:44 PM
pavanbabut's Avatar
pavanbabut pavanbabut is offline
Registered User
 
Join Date: Jul 2004
Location: Fremont. CA
Posts: 1,269
Send a message via MSN to pavanbabut Send a message via Yahoo to pavanbabut
Quote:
Originally Posted by joeaxial
You got me thinking on this 'cause on a typical Front engine/rear drive car, the speed sensor senses transmission rotations and is independent of the final drive ratio. I did some research and found a copy of a tech document concerning our 4eat transmissions published by Subaru at this site http://www.ravensblade-impreza.com/t...ssion/4eat.pdf I'm now quoting from this document:

Vehicle Speed Sensor #1
Vehicle speed sensor #1 is mounted to the transmission and is basically electrical governor pressure. It is used to detect vehicle speed and it effects shift points, lock-up, and line pressure. In FWD transmissions the speed sensor reads parking gear rotation at the front output shaft. In AWD transmissions it senses the transfer clutch drum rotation at the rear output shaft.

Vehicle Speed Sensor #2
Vehicle speed sensor #2 is built into the combination meter. In FWD units, it is used as a back-up for speed sensor #1. In AWD units, it is used as the front output shaft speed sensor.


If I'm reading this doc correctly, #1 takes a reading from the rear output shaft while #2 takes a reading from the front output shaft before the front differential. I took a look at the wiring diagram for my 1992 SVX and it shows that the speedometer is driven by Vehicle Speed Sensor #2. Neither speed sensor would be affected by final drive ratio, so speedometer readings would naturally be inacurate after changing the final drive ratios.

I emailed the tech guy at http://www.terf.com/SpeedChangerPage.htm. He indicated that the SpeedChanger box would work with the Subaru electrical system, but I'm concerned that if it wasn't wired into the correct spot on the harness it could cause the TCU to think that the front wheels would be turning at a different speed than the rear and cause a whole pile of problems.

Any Thoughts?
Steve
Well Well... makes sense, but if we replace everything related to transmission (i mean along with rear differential that is matched to it); how come the front and rear wheels run at different speeds? I didn't get how this goes wrong with the swap. Come on SVX gurus, give us ur ideas on how to rectify this problem. I dont like putting more virtual miles on my speedo, as it makes me to think that my car is becoming older .

I need to know in first place wht causes this problem and secondly how to rectify it.

-Pavan.
Reply With Quote
  #19  
Old 10-05-2005, 07:59 PM
joeaxial joeaxial is offline
Registered User
 
Join Date: Aug 2005
Location: Wales, ND
Posts: 40
Quote:
Originally Posted by pavanbabut
Well Well... makes sense, but if we replace everything related to transmission (i mean along with rear differential that is matched to it); how come the front and rear wheels run at different speeds? I didn't get how this goes wrong with the swap. Come on SVX gurus, give us ur ideas on how to rectify this problem. I dont like putting more virtual miles on my speedo, as it makes me to think that my car is becoming older .

I need to know in first place wht causes this problem and secondly how to rectify it.

-Pavan.
You're right, the only thing that stayed the same after the swap is the speed sensor. You have to remove the sensor that came with the 4.11 donor trans and replace it with the SVX sensor because the donor trans used a two wire sensor while the svx uses a three wire. I wonder what gives?
Steve
__________________
1992 SVX lsl - >111K, pearl, 4.44 gears, ECUtune stage 1
2005 Outback XT wagon - i love that turbo!!!!
2004 Dodge Ram 1500 Hemi
Reply With Quote
  #20  
Old 10-05-2005, 08:03 PM
pavanbabut's Avatar
pavanbabut pavanbabut is offline
Registered User
 
Join Date: Jul 2004
Location: Fremont. CA
Posts: 1,269
Send a message via MSN to pavanbabut Send a message via Yahoo to pavanbabut
Quote:
Originally Posted by joeaxial
You're right, the only thing that stayed the same after the swap is the speed sensor. You have to remove the sensor that came with the 4.11 donor trans and replace it with the SVX sensor because the donor trans used a two wire sensor while the svx uses a three wire. I wonder what gives?
Steve
of course we have to swap the sensors tooo.. since we can't fix our speedo wiring harness which is 3pin to anyother sensor. But the only work it does is to change the mechanical rotations to electrical pulses. But i dont know how it effects in the speedo error. thts seems to be wiered for me..

-Pavan.
Reply With Quote
  #21  
Old 10-05-2005, 09:40 PM
svxfiles's Avatar
svxfiles svxfiles is offline
There's a storm coming.
 
Join Date: Dec 2001
Location: Wiley Ford WV
Posts: 8,650
Significant Technical Input Registered SVX
Gentlemen,
The speedometer sensor is driven by a gear on the passenger side of the front differential.
The amount of rotations of the gear is determined by the tire diameter, and the coefficent of friction, of the tire, controling the amount of rotations, of the axles, in relationship to the ring gear.
THE INTERNAL GEAR RATIOS HAVE NOTHING TO DO WITH THE SPEEDOMETER ACCURACY!
It is only the sensor accuracy, the speedometer accuracy, the wireing, tire diameter, and the ability of the splined shafts to transfer power, that can show inaccuracies!
That said, I would "be really interested" in joeaxial's new transmission # on the bell housing, by the starter.
If the trans came from a 1996 2.5 Legacy, then it should be a 4.44 ratio trans, and his 72 mph at 3000 rpm is correct.
If the trans is a 4.111, and the rpm is 3000 at 72, rather than 77 mph, there is some problem, like its not locking up the torque converter?

Think about this, in first, second, third and forth, the speedometer reads the speed of the car, without reguard to the gears inside the transmission unit.
The reason for this is, it only reads the speed/rotations of the front ring gear.

All cars to some degree have a speedometer error.
The internal ratios are not a factor. Tom
__________________
www.svxfiles.com
The first SuperCharged SVX,
the first 4.44 gears,
the first equal length headers,
the first phenolic spacers,
the first Class Glass fiberglass hood,
the first with 4, 4.44s in his driveway


Fiberglass Hood thread
My locker
4.44 Swap link
Reply With Quote
  #22  
Old 10-05-2005, 09:54 PM
pavanbabut's Avatar
pavanbabut pavanbabut is offline
Registered User
 
Join Date: Jul 2004
Location: Fremont. CA
Posts: 1,269
Send a message via MSN to pavanbabut Send a message via Yahoo to pavanbabut
Quote:
Originally Posted by svxfiles
Gentlemen,
The speedometer sensor is driven by a gear on the passenger side of the front differential.
The amount of rotations of the gear is determined by the tire diameter, and the coefficent of friction, of the tire, controling the amount of rotations, of the axles, in relationship to the ring gear.
THE INTERNAL GEAR RATIOS HAVE NOTHING TO DO WITH THE SPEEDOMETER ACCURACY!
It is only the sensor accuracy, the speedometer accuracy, the wireing, tire diameter, and the ability of the splined shafts to transfer power, that can show inaccuracies!
That said, I would "be really interested" in joeaxial's new transmission # on the bell housing, by the starter.
If the trans came from a 1996 2.5 Legacy, then it should be a 4.44 ratio trans, and his 72 mph at 3000 rpm is correct.
If the trans is a 4.111, and the rpm is 3000 at 72, rather than 77 mph, there is some problem, like its not locking up the torque converter?

Think about this, in first, second, third and forth, the speedometer reads the speed of the car, without reguard to the gears inside the transmission unit.
The reason for this is, it only reads the speed/rotations of the front ring gear.

All cars to some degree have a speedometer error.
The internal ratios are not a factor. Tom
Yep!.. i too agree with your statement, that transmission has nothing to do with speedometer reading. But what we are not able to understand is, why this inaccuracy is showing up in such a noticeable level only when we are swapping the trannies of different ratios other than the stock ratio. Afterall we are using the same stock sensor, if our stock one reads 4mph less as someone above stated, why is it now reading more than 7mph (i mean in percentage increase) when we are using the same sensor, same tires and all that is going to change is transmission. I hope now you got what we are worrying about. In my case it doeasnt matter for me untill I am able to make my speedo show me atleast or approximate to accurate reading.

-Pavan.
Reply With Quote
  #23  
Old 10-05-2005, 10:38 PM
lee lee is offline
Registered User
 
Join Date: Mar 2002
Location: Indialantic, Florida
Posts: 2,940
Quote:
Originally Posted by svxfiles
Gentlemen,
The speedometer sensor is driven by a gear on the passenger side of the front differential.
The amount of rotations of the gear is determined by the tire diameter, and the coefficent of friction, of the tire, controling the amount of rotations, of the axles, in relationship to the ring gear.
...snip... Tom
thanks Tom, I've had the unit apart and just couldn't see any way a gear ratio swap could affect speedo readings, but then I'm a bit challenged and so I thought maybe I was over looking something in the electronics.
Reply With Quote
  #24  
Old 10-06-2005, 03:17 PM
Manarius's Avatar
Manarius Manarius is offline
1995 Subaru SVX LSi Polo Green
 
Join Date: Jul 2005
Location: Grantham, PA (Near Harrisburg)
Posts: 2,119
Send a message via ICQ to Manarius Send a message via AIM to Manarius Send a message via MSN to Manarius Send a message via Yahoo to Manarius Send a message via Skype™ to Manarius
Registered SVX
Quote:
Originally Posted by svxfiles
If the trans came from a 1996 2.5 Legacy, then it should be a 4.44 ratio trans, and his 72 mph at 3000 rpm is correct.
If the trans is a 4.111, and the rpm is 3000 at 72, rather than 77 mph, there is some problem, like its not locking up the torque converter?
My 4.111 geared Legacy turns 70 (acutally 63) mph @ 3000 RPM. (70 on the gauge, 63 for the 10% allowed for small wheels)

And as I recall, on Legacy 4EAT's, the speedo is a cable, not a gear. I may be mistaken however.
__________________
-Jason
(8/23/07-Present) 1995 Subaru SVX LSi (197k) Polo Green (#1102) 03/95
Mods: DDM Tuning 4500k 35w Low Beam HID, 100w H3 Bulbs, Extra Ground Cables, 15 minute $12.96 mod,
svxfiles designed transmission mount (), sporting a "new" tail light bar,
silver BBS rims, custom power steering cooler (one that doesn't dump ATF constantly), new negative lead cable, no more third or fourth gear
(1977-Present) 1977 Chevrolet Corvette (81k) Silver
(12/01/2011-Present) 2005 Subaru Outback 2.5i Limited 5MT (97k)
I have a bad feeling about this.
-Obi Wan Kenobi
Reply With Quote
  #25  
Old 10-06-2005, 03:32 PM
svxfiles's Avatar
svxfiles svxfiles is offline
There's a storm coming.
 
Join Date: Dec 2001
Location: Wiley Ford WV
Posts: 8,650
Significant Technical Input Registered SVX
I am going to pull a 4EAT apart later this week, and post pictures of the speedometer drive gear in the front differential.
Just for the record every 4EAT SVx has a three wire front speed sensor, and every Legacy 4EAT, that I have seen, has had a two wire speed sensor.
__________________
www.svxfiles.com
The first SuperCharged SVX,
the first 4.44 gears,
the first equal length headers,
the first phenolic spacers,
the first Class Glass fiberglass hood,
the first with 4, 4.44s in his driveway


Fiberglass Hood thread
My locker
4.44 Swap link
Reply With Quote
  #26  
Old 10-06-2005, 04:44 PM
oab_au oab_au is offline
Registered User
Subaru Gold Contributor
 
Join Date: Mar 2001
Location: Coffs Harb, Australia.
Posts: 5,032
Significant Technical Input Registered SVX
Quote:
Originally Posted by svxfiles
I am going to pull a 4EAT apart later this week, and post pictures of the speedometer drive gear in the front differential.
Just for the record every 4EAT SVx has a three wire front speed sensor, and every Legacy 4EAT, that I have seen, has had a two wire speed sensor.
The three wires on the SVX unit, are the two normal wires, with a shield wire, to stop any interferance getting in. The Legacy may not have the shield on the wires.

I wonder if the drive gear has a different tooth angle?

Harvey.
__________________
One Arm Bloke.
Tell it like it is!

95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels.
97 Liberty GX Auto sedan. 320,000Kls.
04 Liberty 30R Auto Premium. 92.000kls.
Reply With Quote
  #27  
Old 10-06-2005, 07:21 PM
michael's Avatar
michael michael is offline
What Potholes ???
Subaru Bronze Contributor
 
Join Date: Sep 2002
Location: Scranton, PA
Posts: 2,425
Registered SVX
Not sure if I misssed something or am ovresimplifying but. Couldn't you follow a friend going say 60 according to their accurate speedometer, set your cruise control and properly reposition the needle at 60mph. A passenger might be helpful,along with a nice straight empty road.
__________________
"The things you own end up owning you. It's only after you lose everything that you're free to do anything."

92 Pearl White Ls-l (138k) Euro Headlights & Blinkers, 97 Grill, Euro Tail Lights, SS Brake Lines, Stebro Exhaust, Slotted Rotors, Classic Registration
96 Legacy Outback (206k) 5-speed 2.2 Lightweight Crank Pulley, Group N Trans & Motor Mounts SOLD
Wanted: Steering Wheel
Reply With Quote
  #28  
Old 10-06-2005, 07:28 PM
pavanbabut's Avatar
pavanbabut pavanbabut is offline
Registered User
 
Join Date: Jul 2004
Location: Fremont. CA
Posts: 1,269
Send a message via MSN to pavanbabut Send a message via Yahoo to pavanbabut
Quote:
Originally Posted by michael
Not sure if I misssed something or am ovresimplifying but. Couldn't you follow a friend going say 60 according to their accurate speedometer, set your cruise control and properly reposition the needle at 60mph. A passenger might be helpful,along with a nice straight empty road.
Yeh.. of course that is one way to check the speedo accuracy, but not all speedos are accurate and i myself checked with a radar meter on the road and I personally can feel the inaccuracy and can tell for sure my speedo shows over reading than the actual speed.

Coming to repositioning, this variation is not by a fixed value. But its a proportionate difference depending upon the speed of ur vehicle and changes according to it.

-Pavan.
Reply With Quote
  #29  
Old 10-06-2005, 08:18 PM
svxfiles's Avatar
svxfiles svxfiles is offline
There's a storm coming.
 
Join Date: Dec 2001
Location: Wiley Ford WV
Posts: 8,650
Significant Technical Input Registered SVX
Quote:
Originally Posted by oab_au
The three wires on the SVX unit, are the two normal wires, with a shield wire, to stop any interferance getting in. The Legacy may not have the shield on the wires.

I wonder if the drive gear has a different tooth angle?

Harvey.
Since all the transmissions I have looked at were WV and MD transmissions, there is NO UNIFORMITY TO THE TEETH!!!






OK, that was fun....



As long as the teeth were of the same #, and they drove each other, the angle is not important.
However, the HAL effect speedometer sensor COULD be affected by the distance when seated. I do not know this for certain, but it "sounds logical"
Harvey, can the third wire be a shielding wire if it does not surrond the two pulse carring wires?
__________________
www.svxfiles.com
The first SuperCharged SVX,
the first 4.44 gears,
the first equal length headers,
the first phenolic spacers,
the first Class Glass fiberglass hood,
the first with 4, 4.44s in his driveway


Fiberglass Hood thread
My locker
4.44 Swap link
Reply With Quote
  #30  
Old 10-07-2005, 10:57 AM
pavanbabut's Avatar
pavanbabut pavanbabut is offline
Registered User
 
Join Date: Jul 2004
Location: Fremont. CA
Posts: 1,269
Send a message via MSN to pavanbabut Send a message via Yahoo to pavanbabut
Guys, come on, some one help us what we can do to rectify this. We are not saying that the speedo off is due to transmission faults or someother. Just we don't know what's causing this. Give us your ideas on what we can do. As far as we can say-

1) There is no mismatch of tire sizes and they are all of stock size and are same as they are on old tranny.
2) Stock speed sensor is installed

we are trying to say tht the only ones that are been changed are the tranny and the rear end. Hope now you can get what we are trying to say.

-Pavan.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 04:49 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
© 2001-2015 SVX World Network
(208)-906-1122