Speedometer 20MPH over what it should be

[chrismc410]

Hi

I have a 1985 Supra, analog cluster, as far as I know, everything on the car is stock. the speedometer is off by 20MPH. In other words, if it says 40MPH, its doing 20MPH. Tires are exactly what they should be according to the glove box, wheels are stock. I tried a new cluster, same thing. I'm at a loss on what else it could be. I keep hearing about a gear, but I cannot find this gear and should be a gear in the cluster, both the replacement cluster and the old cluster gears look fine.

Any sugesstions? If I cannot fix this problem, car will be sold ASAP, can't have a car with a defective piece of vital equipment


Thanks

[Tanya]

either the speedo gear in the tranny is wrong and/or your rear end has been swapped for something else.

[Malibyte]

Or, as more commonly happens, the spring attached to the needle gets a little weak and offers less resistance. My '84 was doing the same thing...it was reading about 10% over actual speed. Funny thing is, since I swapped out the 4.30s for 3.90s, it's now about right. The math is pretty close. :p

[chrismc410]

How is this repairable? If its repairable at all, and if so, how much will it run and where do I have to take it to do it?

Thanks

[jugalo]

Both of my cars do the same exact thing!
HELP US!!!

[ZZT231]

Buy another second hand instrument panel and try to see if it is the needle spring...

[Supra_devil]

Buy another second hand instrument panel and try to see if it is the needle spring...


...... I tried a new cluster, same thing. Thanks.......


some how i doubt both clusters were off the same amount, therefore the springs probably not the issue. i would check for a possible swapped tranny, with the wrong speedo gears.

[ZZT231]

Thanks Supra_Devel for highlighting out the cluster being swapped... Didn't see that...
Maybe diff maybe swapped, or transmission speedo gear might be different.

[KesekiSupra]

wat about the speedo cable itself?

[Supra_devil]

the speedo cable turns the same on all our cars, it won't change anything. IF it was going it would read slower, not faster.

[chrismc410]

If the rear end has been swapped, what can be done about that? If the previous owner did that, is the a way to correct the speedometer without changing the rear end? and if the transmission has been changed, what gear do I need to correct it? I keep hearing there is a gear thats at least 31 teeth, and according to the Toyota dealer, there are five possible gears that can be used. So again, what gear do I need if its a transmission issue or how can I correct the rear end issue if it is that without changing the rear end?

Thanks

[Rich64N]

My speedo has been off by 7% from the day if rolled off the floor room, with the original Bridgestone Potenzas. I do the math in my head.

[Supra_GT_R]

driver 20 mph slower :P

[Funkycheeze]

http://www.celicasupra.com/vbforums/showthread.php?t=10668

its all covered there, i even maid an excel spreadsheet to calc the gear you need, and all the pns for the avaliable gears - you just need to take the one out of your tranny to figure out which one you need - id say one thats at least 1 or 2 teeth smaller

[chrismc410]

How do I tell what ratio I have? I don't have enough mechanical aptitude to do this. Is it stamped anywhere on the car? Or will the VIN tell?


Thanks

[jugalo]

http://www.celicasupra.com/vbforums/showthread.php?t=10668

its all covered there, i even maid an excel spreadsheet to calc the gear you need, and all the pns for the avaliable gears - you just need to take the one out of your tranny to figure out which one you need - id say one thats at least 1 or 2 teeth smaller

That still doesnt address the problem...which is that BOTH of my cars are bone stock, one with auto and one with manual, yet they both are way off.

[CJSREDPRA]

How do I tell what ratio I have? I don't have enough mechanical aptitude to do this. Is it stamped anywhere on the car? Or will the VIN tell?


Thanks

Have you used the search feature yet??? Many MANY postings on how to look up your rear diff code & how you can do this by spinning the axle by hand.

[SilverMk2]

How exactly are you measuring the actual speed? When the gauge says 40 and you are doing 20 that's a huge error. If your measurements are accurate and you are a constant 20mph off you probably have something wrong with the cluster. The needle has slipped or something. If you have a gearing/tire change the difference is going to be a percentage different. I'd try to find a speedo shop nearby to calibrate everything.

[chrismc410]

I was being paced and one person was doing 65 and in order for me to keep that speed, I had to do 85. That and the police had one of those readers that tell you your speed, and that showed 20 MPH when the needle read 40MPH. It did the same thing with two different clusters. So I don't think the dash is the issue. I've already spent a good deal of money trying to resolve it with no success dash wise, which prompted the decision to sell the car if this is not corrected on this last attempt. If the car ends up being sold, Which years used an electrical dash instead of cable driven? 1986.5 and up? so this problem can be avoided in the future.


Thanks

[RedP85]

A rear end swap with different gear ratio would give a % error of reading, ie:
at 40, + 10% = 44 read -> error of 4
at 50, + 10% = 55 read -> error of 5
at 60, +10% = 66 read -> error of 6, etc etc
a constant error of 20 means it has to be the clusters, both.

[Dangerous Ken]

Reading through this thread, I wonder if you have a Digital cluster?
They are different part numbers 82, 83, 84+, and auto or 5 speed specific clusters do matter.

Ken

[chrismc410]

No, its an analog cluster with a 5 speed transmission

[Junkie]

20mph across the needle span,on 2 clusters ?

On an 84 with stock trans,3.42 gears,at 30 indicated,actual on radar was 32-5 .At 60-80 indicated,running next to a car known to be accurate,actual was 80-100 , so + 2-5 low speed,+ 20 just under 100mph.

Either you have 2 messed up clusters,or got the #'s wrong somehow/somewhere.

Really would like to help,but there are no known gearing combos in the trans,or rear end,except the above,where you can even get close to 20mph off.


:p indicated 130 "pegged speedo" clocked on GPS at 153 :p

[chrismc410]

Thanks for your help, I think I will just sell the car to someone more capable of dealing with it. I'm sorry, just something like that I'm not ok with and I don't have the expertise or the money to continue to try to fix it. I think the Mark III Supras aren't cable driven speedometers and hence less likely to go wrong.

Again, thank you

[CJSREDPRA]

I think the Mark III Supras aren't cable driven speedometers and hence less likely to go wrong.

Says who???????????????????????

<----------------- Has had to remove the dash cluster from a 87T to get the components for the Supra Monitor that I sold on eBay..... There IS a speedo cable to disconnect.......

[SilverMk2]

Buy a MkIV they have electronic speedo. Expensive way to fix what should be a simple problem.

[chrismc410]

Is there any year that has an electronically driven cluster?

Thanks

[CJSREDPRA]

Aaron just answered your question above.....

MKI's, MKII's & MKIII's are ALL cable driven..... Does not matter if it's a analog dash or digital display dash....

[chrismc410]

I've already dumped over $3000 into fixing this and other problems thats including the $1800 for the inital purchase. Seems I made a financial error in this car. No harm done, except to my wallet. Again, thank you.

[chrismc410]

Will a Celica's cluster work in it? They look simular Figure another $50 for a cluster from it if it will work might be worth a try before condemning the car

[RedP85]

Celica cluster will definitivaly screw up the tach needed, as 4 cylinders vs 6.
4 pulses for Celica vs 6 in the Supra for each revolution. Will show 4500 RPM when actually is 3000 ! The speed section should be direct swap, as same tranny, but again rear diff ratio may way (I don't know them)

[chrismc410]

The Tach in the old one says about 3100 RPM at "85" MPH so I assume you can take the old tach out and put it in its place?

[RedP85]

I never opened an analogue tach, but I guess they are made modular.
Sombody else ?

[lechner]

No, its an analog cluster with a 5 speed transmissionWell, in that case, I'm curious what gear you are in and what RPM the tacho indicates when the speedo indicates 60 mph. And does your speedo indicate MPH, or KPH? Cause 40 KPH is about 22 MPH.

[chrismc410]

its a MPH gauge and its its in 3rd and 4th gears that indicate 55-60MPH, driving around town. When the needle says 20-30 in town, people go right by you by a good margin and two, according to the radar, I'm going 10 when the needle says 20MPH or 20 when it says 40 and so on, no matter what gear you're in, 85, you're doing 65

[RedP85]

that is a soo big error !
Does on the side of the highways nearby your place have mileage posts every miles ?
If so notice the cluster miles value, including 1/10th, and keep going until the next post.
That will tell rapidly if there is a gearing error, or a needle error.
same as posts = needle error,
different as posts = gearing error.

[Dangerous Ken]

Will a Celica's cluster work in it? They look simular Figure another $50 for a cluster from it if it will work might be worth a try before condemning the car

What sticks out to me is the lower redline markings on the celica cluster, rather than supra cluster.

And if that's the very edge that you are on about the car, I have a cluster that you can have for the price of shipping. The 'stalks' on the lower left broke when it got shipped to me, but you can't argue with free to change your outlook toward the car.

Ken

[chrismc410]

Which kind of cluster is it from? Is it from a Celica or a Supra and what would be the cost to ship it to VA?

Thanks



What sticks out to me is the lower redline markings on the celica cluster, rather than supra cluster.

And if that's the very edge that you are on about the car, I have a cluster that you can have for the price of shipping. The 'stalks' on the lower left broke when it got shipped to me, but you can't argue with free to change your outlook toward the car.

Ken

[Dangerous Ken]

It's a 130mph supra cluster.
Should be under $10 to ship to va.

Ken

[SilverMk2]

When it comes to speedo errors the important questions are

Do you have factory sized tires?
Do you have the right rear diff ratio?
Do you have the right speedo gear combo?
Are you still using the original W58 transmission?
Is the instrument cluster working correctly?

These are the only things that matter for the speedometer.

Probably what you should do is go by one of those speed signs at like 3 different speeds and report the engine RPM and gear for the speed. If you've got a tire size you should be able to figure out what rear gear you have. One thing you might want to check is the condition of the trans speedo gears. If some of the teeth are stripped you could have a major error.

[chrismc410]

I can answer two of those questions, one yes, they are the original tires. Two, I believe its the same transmission. As far as the speed gears, that I dont know. And I dont know how to look for the right ratio for the rear differential. Two clusters are reporting 20MPH over, so either I have two bad ones, or they both are right. There is more than one gear? Where is the other gear? I know one is on the side of the trasmission, where is there other one?


When it comes to speedo errors the important questions are

Do you have factory sized tires?
Do you have the right rear diff ratio?
Do you have the right speedo gear combo?
Are you still using the original W58 transmission?
Is the instrument cluster working correctly?

These are the only things that matter for the speedometer.

Probably what you should do is go by one of those speed signs at like 3 different speeds and report the engine RPM and gear for the speed. If you've got a tire size you should be able to figure out what rear gear you have. One thing you might want to check is the condition of the trans speedo gears. If some of the teeth are stripped you could have a major error.

[DADSPRA85]

where in VA are you i have clusters that we change out first to see if it works
my speedo is a little off but no where near 20mph

brendan

[chrismc410]

I'm in Front Royal, VA, says you're near Richmond





where in VA are you i have clusters that we change out first to see if it works
my speedo is a little off but no where near 20mph

brendan

[Dangerous Ken]

Shipped a 130mph supra speedo cluster today.
Chris overnighted! $10, $14 for the overnight letter.

Hope it works out for you.

Ken

[chrismc410]

Had the car on a lift today, no tag can be found on the rear differential, but did find the gear for the transmission that drives the speedometer, its stamped 33/11. The rear looks like its original, what should the rear end ratio be on a 1985 Supra, P type? Transmission is questionable, no tag on it, and the front cover for it is gone and been gone since I've bought it, the mechanic has reason to believe the transmission was swapped out, so I dont know if it is the right transmission in the car now, should be a w58 transmission. But didn't Toyota use this in other cars too? Mechanic suspects this transmission came out of a truck

Thanks

[SilverMk2]

If its a 5 spd it should be a 4.30 for an automatic 4.10. An easy way to check this is to see how many turns the driveshaft does when the tires rotate once. If it goes around 4.3 times its a 4.30 and so on. The w series trans are used in lots of cars, supras, trucks, celicas....

[Carlos Brown]

Chris,

You may be on to something here because a 33/11 speedo gear set is suited for a 3:73 rearend, not a 4:30. Of course you still need to verify which rear is installed in the car currently. If it is in-fact a 4:30 rear, someone may have changed the tranny out and used an early model (82) one...

What do you think guys?

Regards,

Carlos

[Dangerous Ken]

Just is odd that someone would switch out the normal tooth gear and Not mess with the internals too. I'd think most would do whatever gear change and Then think to try to compensate to the correct speed reading by getting the right tooth gear.

For 20mph off though; the turbo folk here would be interested in the 'wrong' internal gears you have...

Ken

[chrismc410]

If it is in fact the wrong transmission, my mechanic suspects (which is also a transmission shop as well as general repairs) someone simply dropped this in since the front dust cover on it is missing without regard as to whether or not this is the right year, is there a way to make this one work right? or is it cheaper and easier to buy the correct year transmission, used of course. The cost of a rebuilt or new one is a bit much.

Thanks

[RedP85]

Even with a "3.73" drive gear, while the system was suppose to be "4.30" still only make:
85*3.73/4.30= 74 still far from 65..

[Junkie]

Like I said,the ONLY car I have seen 20mph off at ANY speed is Ophirs car.If you use the 3.73 rear end,or a tranny from a 3.73 car,10mph off would be correct as Jocelyn pointed out.We have the 4.30 set in the trans,and 3.42 gears in the rear,in O's car,and it DOES read 20mph off at speed.Has been verified by at least 3 known correct "or close enough" cars.Since I can't seem to find a trick trans from a 3.42 rear truck,I have not been able to rob the parts to make it read correctly.
Wish I could be more help,when you do figure it out,let us know what you find.This one is a bit strange.

[Carlos Brown]

Chris,

Based on the available speedo gear sets, the best you will be able to do (without changing out your drive gear) is a 35/11 combo @ 8% error. With the current 33/11 gearset you should be running at about a 15% error.

Therefore, your solutions will include changing the drive gear to the #10 tooth and then installing a 35 tooth driven gear, or replace the tranny with one that already has a 10 tooth drive gear installed. Remember that with a 4:30 rear gear you will need to achieve near a 3.5 speedo gear ratio (eg. 35/10). Send me a PM and I will send you a 35 tooth driven gear (for a 35/10 set).

Junkie,

For the set-up that you are running, the numbers come up saying you need a 2.8 ratio for a 3.42 rear gear and stock height tires. You can achieve this by using a 31/11 @ 2.82 for a 1% error (NOTE: A 32/11 will give you a 2.91 @ 4% error).

Regards,

Carlos

[Junkie]

Carlos............YOU ROCK !!! i have never taken the time to figure out what was needed.I just clock the car,adjust my driving as needed.Enough other issues to deal with on a performance car,that was like last on the list,LOL.

[chrismc410]

I found out I have a 4:30 gear ratio, mechanic says it has it stamped on one of the gears back on the rear. So the rear is right, the gauges are right, so the key must be the transmission? How hard is it to find the 10 tooth gear thats needed inside the transmission? If it involves almost rebuilding the transmission, will replace it with one that has the right gear

[chrismc410]

The saga continues, I have the 35T gear now it wont go in. I ordered the 10T gear since what was in the car was a 33/11 gear. How do you get to the 10 or 11T gear? Or does that require a transmission rebuild. If a rebuild is needed, then I will sell the car.

Thanks

[Carlos Brown]

Chris,

You may want to take a look at the TSRM on line as they will have an exploded view of the tranny internals. You will see the speedo drive gear near the end of the output shaft. As you scroll through the pages you will get an idea of what you are looking at...

http://www.cygnusx1.net/supra/library/TSRM_MKII/mt/MT_005.html .

Regards,

Carlos

[chrismc410]

We have the gear in, still can't drive it yet, the gearshift isn't set right. So the shop has to pull the tailshaft off and try again. We're hoping this will do it. When we put the 10T gear in, the 35T went right in. Again, we have hopes this will resolve the problem. We did find the internal parts of the transmission don't look worn, and suspects this trasmission may have come from an 82 or 83 car and someone didn't bother to swap the gears for an 85 car, since the rear ends are diiferent.

[chrismc410]

Hi,

I now have the 35 and 10T gears in the transmission, now it seems accurate, when the needle says 20 in town people aren't passing me anymore. Thanks for all your help

[Carlos Brown]

Chris,

I am glad to hear that you got your speedo issues worked out, that you found a mechanic to take on the job, and that you had the patience to stick with it and see it through. I hope you enjoy your new ride and I also hope that it gives lots of trouble free miles...

Regards,

Carlos

[RedP85]

I'm with Carlos above.
This tiny problem probably cost you much more than it's 'value',
but when you got to do it...

[Dangerous Ken]

Glad to hear it's fixed from suggestions from the mkII lovers here.



when the needle says 20 in town people aren't passing me anymore

Sounds like you were driving a geo metro for a while :)

Ken

[pdupler]

To revive an old tread, I know many of you were still left with a problem. I just visited a speedo shop on another issue and while there, I asked for those who have all stock parts and the speedo is still off, how this happens and how to fix it. The guy there has been in the speedo business since 1960 so I'm guessing he knows his business. This is what he said. Older Toyotas and Nissans with cable driven speedos are notorious for reading high and he has repaired many. He said grease from the cable migrates up through and into the speedo head causing it to read high. A another taletell sign he said is that if you stop quickly, the needle doesn't fall as quickly as you decelerate or may not fall all the way back to zero every time. A speedometer shop can take the speedo head apart, clean, lubricate, test and certify its accuracy. HTH.

[Donn29]

Damn, my 97 swift does this. take your foot off the gas, wait, then the speedo changes. Now I gotta fix that, and figure out why my Supra's Digital cluster can't decide what speed to show for more than half a second.
THANKS Phil!

[brandon82mk2]

i think the same as some of the other readers its something to do with rear differentials. you need to find out what gear ratio you have. I know for a fact 4 different rears if not a whole lot more came out from the factory. is your supra a p-type or an l-type and could it have the rear from one or the other being wichever car type you have. strange stuff

[Jose H. 3]

i think the same as some of the other readers its something to do with rear differentials. you need to find out what gear ratio you have. I know for a fact 4 different rears if not a whole lot more came out from the factory. is your supra a p-type or an l-type and could it have the rear from one or the other being wichever car type you have. strange stuff


--if you read the whole tread, you would have known the original problem this thread started for was solved (post #58)... phil just brought it back up again to help out others that have other probs with the actual speedo... not the gears... any of them... plus, a lot of your other questions were also answered in the tread already :hsugh: