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Discussion Starter · #1 ·
I just finally got my Suzuki back on the road! So a recap since I am new here...1995 4 Door Sidekick JLX. 5 speed, 4x4.
I had to replace the transmission. I bought a 1997 Sidekick, 5 speed, 4x4 with a "bad engine" for $200 and pulled the transmission/t-case from the '97 parts rig and put mine back together. The rear diff in my '95 was super noisy, so I pulled the rear end from the '97 as well. Got it all put together today. Put my GPS on the dash, and as it turns out, now my speedo is about 15 or so MPH off. It was within 2 or 3 MPH before. All I can figure is there must be a difference between the speedo gear setup or the speedometer head itself between the 2 years. Can anyone shed any insight on this?
The speedo was also off with the '97 trans/case and original rear diff. As far as I can decipher the diffs should be the same ratio. As far as I could count tire revolution wise the "new" diff is a 5.12 as well as the old unit.
 

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speedo showing 15 mph too fast or too slow and at what speed?
if its too slow it could be just the cable not engaging fully
a 15mph error at 30 is not the same as at 60...
Then do an easy check: plan on the gps a trip ad note how many miles it is going to take, zero the trip counter and do the trip, compare numbers...
have to add that also my Vitara's speedo is extremely accurate, just a few km/h off at 100, almost zero error on trip meter over very long distances.
 

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A parts catalog lookup shows the same part number for the speedo drive gears and also the front ring & pinions in the manual transmission 95 & 97, the numbers for the actual speedometers are different, which I believe is due to the different design more than anything else - the fact that the axle ratios are the same and the speedo drive gears are the same suggests that the actual speedometer should have the same rev/mile ratio.
 

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Discussion Starter · #4 ·
Okay, did leave out the vital info on this...when the GPS is reading 65ish, we are over 80 on the dash. I am wondering about swapping the dash from the '97 to see if the speedo reads differently. It is frustrating, because before the speedo was pretty accurate, especially considering I have oversize tires. It was not perfect, but close enough I didn't worry about it.
 

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Discussion Starter · #5 · (Edited)
So, more info gathered, and more interesting as it goes along...
When I started driving the little monster a week ago the speedo was reading 15 mph or so fast at highway speed. Now, it is reading around 9 mph fast. Also, this morning I reset the trip on the dash and on my GPS. The GPS showed we travelled 31.5 miles and the dash 29.8. So my speedo is reading fast, and the odometer is running slow. I have 235/75/15 tires on the thing, which is around 6.6% larger than stock tire size. Doing the math, the 29.8 on the dash multiplied by the 6.6% oversize comes out to 31.7. So the odometer is almost dead on where it is expected to be with oversize tires, but the speedo is acting like the tires are undersized.
Real brain itcher here!
 

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If your odometer is working, then it indicates that the cable, etc.,is ok. But there are other components to the speedometer itself, as indicated above.
 

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Discussion Starter · #7 ·
Thanks Bex! Now I have some info to dig with!
 

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odo/speedos are known to have varying degrees of accuracy that are not necessarily matched,
the odo in all the subarus i had was always spot on while the speed reading was easily 10% too high.
explanation? odo counting is based on gears, so no wear. in speedos, there's a magnet creating eddy current in a concentric cup, any little change in distance between them throws speedo reading off.
is it an issue at all now with free accurate speedos in your phone?
 

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Discussion Starter · #9 ·
No speedo apps for a flip phone! I suppose pulling the cluster and cleaning/inspecting the speedo is in order. At this point it will have to wait until late July. Starting Saturday I begin my busy season, working 12-14 hours a day, 7 days a week. It is really boggling the ole brain though. Today when I took my son to his baseball game the speedo was only about 5 mph off of what the GPS was showing. I have never before this compared mileage readings between the GPS and odometer, but when I was driving the vehicle daily 3 years ago, the speedo registered within a mile or 2 off of actual, or at least close enough I just drove it like it was accurate with no worries. As I stated above, after doing a comparison of Odometer readings, it is pretty much dead on with what I would expect with my tire size.
 

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sure, if you have a NAV thing with GPS, accuracy is just as good as a smartphone, if not better
save yourself the trouble of dismantling the speedo cluster, you will not find there anything that you can fix/service/calibrate, at least from my experience.
 

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LOL….well, it appears that whatever the issue is, it is beginning to ‘self-correct’: first 15 mph off, then 9mph off and now 5 mph off. Maybe by next week it will be accurate??? ;)
 

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save yourself the trouble of dismantling the speedo cluster, you will not find there anything that you can fix/service/calibrate, at least from my experience.
I haven't pulled apart a gen one speedometer, but, on the cable driven "spinning disk" style, the needle return hair spring is usually adjustable - trying to calibrate it by trial & error however is likely to be an exercise in frustration.
 

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i used to mess around when i was a poor student with the Smiths-Jaeger speedos on my old brit-bikes, the really old ones had an amazing clockwork mechanism inside which you could oil and tune.

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the newer ones with magnet/eddy current/spring? not enough of a challenge compared to this :) ...
 
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