our 1996 outback is 1 mph off for every 10 mph. I was going 72 down the highway and found myself getting a ticket for 79 mph. how is the speedometer that slow? the car has the correct sized tires on it 205/70-15. we can't figure out what's making it that far off. we checked the speedometer with a gps speedometer app on my phone and sure enough its off. cop wasn't lying. could be because of the wiring in the dash? I replaced the hole dash with one out of a legacy L sedan.

I replaced the hole dash with one out of a legacy L sedan. 

 

That's probably the problem as the Legacy and Outback have different final drive ratios and the speedometers are calibrated differently for these two ratios. 

well, I left something out. I'm still using the outbacks speedometer/gauge cluster. would the wiring harness in the dash be different? I thought the ecu tells the dash how fast your going

the problem is either the speedo it self or the trans .

 

does the speedo go up to 120 or 140?

the outbacks usually have a different ''face plate'' then the lego.

in my experience, the legos go up to 140, and the outbacks only go up to 120.

this is a function of using the same speedo for both models,

but adapting it to work correctly for the different ratios and tires.

 

if the trans was swapped (rear diff too) with one from a lego L or brighton,

the speedo drive gears in the trans do not match the tires or speedo.

this MAY be correctable by swapping in the matching speedo.

(EDIT: i don't think so but smaller tires may help. or a combination of the two.)

or if not absolutely correctable at least making the error much less.

 

 

to check and see if the trans has been replaced,

read the trans ID# on the bell housing at the starter.

it is a a 10 character ID#.

please post all 10 here.

it will start with TZ102Z.......

please be accurate.

Edited September 30, 201312 yr by johnceggleston

95 and maybe 96 have the 140mph speedo, and 97-99 have 120mph across the board, difference being ej25 equiped cars(whether outback, gt, or lsi) got red indicator needles, and the ej22 cars got white needles.  The wiring in the dash makes no difference, it just sends the signals. 

the trans code on that plate on the strut tower says TZ102Z2ABA but the trans is TZ102Z2AAA. would that make any difference?

the trans code on that plate on the strut tower says

 

TZ102Z2ABA - this is the 96 outback auto trans

 

TZ102Z2AAA - this is a 4.44 final drive ratio trans, but not an outback.

it is either a GT or LSi trans, probably an LSi.

this means that the speedo is geared for smaller tires.

 

the GT tires are 205/55/16 which is about 1.5 inches smaller in diameter than the outback 205/70/15 tires.

but iirc, the LSi tires are are the same size as the lego L and brighton, 185/70/14 (or probably 195/60/15 on 15" alloys)

 

this tire size difference (LSi to OBW) explains 8.6% of the speedo error (79 / 72 = 10.9%).

so i think you have found your error.

 

the best way to calculate your actual error is to clock 100 miles with the odo and the GPS  during a long trip.

what ever the difference is when the slow one hits 100 miles is the error.

 

the next time you need tires you can buy slightly smaller ones to reduce the the error.

it will also reduce the height of the car.

 

another solution is to remove the needle on the speedo and reset it to 65 when actually driving 65.

this is very complicated, and can be very dangerous.

i posted the tale years ago of my experience .

i was putting a 96 lego speedo in a 97 GT.

if you search you should find it.

this link shows the TZ102Z2AAA trans was used in the 96 LSi.

 

http://opposedforces.com/parts/legacy/us_b11/type_30/automatic_transmission/at_transmission_assembly/

 

it also shows it was used in the 96 GT.

(click on the part number and then ''usage info'')

 

there is a 2.7% tire size difference between the GT and LSi.

this means one one, or both of them, left the factory with a speedo error.

or, I could go to the guy who did the transmission work. he got us a new case and rebuilt it cause the original trans was too wore out. this sounds like his error and he should have to fix it.

he may have charged for a rebuild,

but he actually did a replacement.

 

good luck with that.

haha. lol. I'm forgetting my own crap. we got that trans from a scrap yard. we handed it over to him to be rebuilt when he told us our original trans was too wore out.