Just changed gears, why is my speedo still accurate?

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Blenderhead

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This weekend I swapped the 3.27s for a set of 3.73s in my 98 LSC. I didn't have the correct speedo gear at the time, so I figured I would just change it out some time this week. Well after the swap it seemed like I was at a higher rpm for the same speed showing on the speedo, even without changing the gear, and I double checked it this morning by calculating out what speed I should be at a given rpm and what the speedo is showing, and sure enough, the speedo is still accurate, even before changing out the speedo gear. Does the speedo work off the wheel speed sensor or something weird like that?
 
I could have sworn the speedo jumps up when I lose traction. I'll have to double check that. So if it works off the wheel speed sensor, is there any reason to put the new gear in the trans?
 
Blenderhead said:
is there any reason to put the new gear in the trans?
Click to expand...

for such a minor gear change, I doubt it.

The adaptive learning in the second gens will "account" for up to two ratios in either direction.

For instance..

307s to 327 or 355 (no worries)
from 327 to 355 to 373's (no worries)

but if you jump from 307's to 373's you are outside the adaptive learning of the PCM...

hope that made sense.


Now with that said..are you feeling MUCH of a difference between the 327's and 373's?

When I went from 307's to 373's I was disapointed in how "small" the change actually was, and how little performance feel was increased.

I regretted such a small gear change from the first dragstrip pass til the day the car was stolen.

IMHO if you already have 327 gears and you do anything less than 410 or 430 the end result will be a disapointment.
 
Does the T45 have a speedo gear and an OSS?
If so, are they plugged in?
 
Well I have a T45 in the car as well. I would think if I still had the auto, it wouldn't be as noticable an improvement, but with the 5-speed the 3.73s are absolutely perfect. I drive fast on the highway, generally cruising about 80-85, so 4.10s would have been too much gear for me. I actually didn't think it would be that big of an improvement going to the 3.73s from 3.27s, but I'm very happy with it. Plus with the 5-speed, any more would have made 1st gear way too short. Before the gear change, the car would pull nice through first and second, but then completely bog down going into 3rd. Now it pulls much harder through first and second, and keeps pulling hard through 3rd as well. By the time I wind out 3rd gear, I'm well over 100mph. Also on the highway, dropping it down to 3rd used to not be quite enough to pass someone, and dropping down to 2nd was way too much. Now dropping it down to 3rd at 70, the car just takes off. I'm quite happy with it, and I definitely think 3.73s and a 5-speed are the way these cars should have come from the factory.
 
The T45 does have a speedo gear, and it is plugged in. No OSS though. I was just surprised cause I thought the speedometer went off of the speedo gear, but it continued to read correctly after the gear swap without changing the speedo gear. Now I need to know if there is any reason to bother putting the correct speedo gear in there.
 
Blenderhead said:
Plus with the 5-speed, any more would have made 1st gear way too short.
Click to expand...

I agree..
My SVO had 410's and first gear lasted about 8 feet literally.
making a gear change before the 60' clocks wasn't very conducive to low ets..LMAO
 
Blenderhead said:
The T45 does have a speedo gear, and it is plugged in. No OSS though. I was just surprised cause I thought the speedometer went off of the speedo gear, but it continued to read correctly after the gear swap without changing the speedo gear. Now I need to know if there is any reason to bother putting the correct speedo gear in there.
Click to expand...


well if you had a 4r70w I'd say yes.. to help with the shift and TC lock up schedules.

but since you dont.. I'd lean towards "not messing with it" unless it becomes a problem.
 
Well it must be going off the rear wheel speed sensors, not the front, because when I break the tires loose the speedo jumps up. I looked up the wiring diagram, and the speed sensor in the trans is used for the variable assist power steering and also the ride height, so probably this weekend I will put the right gear in there.
 
i was gonna chime in and say rear. i learned yesterday, cuz my RR crapped out on me. it sucked the abs light came on and trac control lights came on as it knocked me down to a crawl and the speedo went ape shyt. it was funny i got to work and put in park and the speedo head was still jumping all around

oh and a side note ford has completely discontinued all of our wheel speed sensors, all years........theres still lots of motorcraft ones online though so ford sold off there stock, so when there gone there gone. and supposedly the 98 has a specific RR sensor (of course :rolleyes:) 97 the rears are the same
 
That is a massive bummer.... I have been wanting to find some spares...

I really want to know what makes the 98 year specific... cause that is BS.
 
If it's anything like the VII's it's just the plug/connector that changed on the sensors...
 
dont matter, 97 are just as discontinued as the 98's odd one, but yeah pin location could be it, dunno. hell kid dont solder, just repin the connector
 
If I get some time to go hit up a yard and look around I'm going to try and get a 93-97 sensor set and a 98 set and really try and figure it out.... I've heard that 93-97 interchange.
 
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