Thanks to the State of West Virginia I now know my speedometer is slow

[Nocheez]

I converted to a 5-speed a couple months ago and thought my drop in gas mileage was due to the different gearing and the fact that I've been enjoying rowing through the gears.

Last night I left Charlotte to head to Ohio for vacation. In Charleston, WV I got pulled over and was very confused as I had my cruise set at about 8 over, and I've been driving that way for years and never been pulled over for it. The officer claimed I was doing 74 in a 60, but I thought he was trying to make cash off of me. I took my ticket, didn't argue, and continued on.

I got the idea to start checking my trip odometer against the mile markers and sure enough, it wasn't lining up. My car was somewhere around 10% off, meaning I had been blasting through most of my trip at around 85 MPH! I'm lucky I got pulled over when I did, it could have been a lot more expensive.

Anyways, I've still got the old speedometer gear (at home in Charlotte) from my automatic. I've got 3.73 rear end gears, and I'm assuming that the R154 I'm running now has a different speedometer gear in it, maybe it was from a 4.3 rear-end car. I never bothered to check it before since I assumed all turbos had a 3.73 rear end.

Can someone confirm that all I'll need to do is swap over to my old gear, and that it's a plug and play affair?

Thanks!

P.S. I'm not whining about my ticket, I was speeding and got pulled over for it. I wasn't purposely going as fast as I was written for, but it's probably not even worth fighting it.

 

[foreverpsycotic]

Not possible that it was a 4.3, that only came in NA cars with a w58 or a340. More likely it was a 3.91 car.

It is always worth fighting a ticket, more likely than not, you will have a reduction in fine or points.

 

[Nocheez]

Not possible that it was a 4.3, that only came in NA cars with a w58 or a340. More likely it was a 3.91 car.

It is always worth fighting a ticket, more likely than not, you will have a reduction in fine or points.

It's not worth it when it'll cost twice the price of the ticket in gas to drive up to fight it, plus the lost time at work.

Just did some math, I stopped at exit 93 in North Carolina to gas up and stopped again in Ohio at exit 6. My odometer indicated 243.4 miles, while I actually travelled 273.6 (according to Streets and Trips). That's 12.4% difference!!!

I also put 275/40/R17 tires on the back, so I'm sure that's a small portion of it, but damn!

 

[deabionni]

There was a thread that was posted last October from a guy that worked at a shop that could make a ratio-adapter for your speedometer, and make it accurate again. Might be worth checking something like that out, that way your speedometer can stay accurate no matter what changes you make to tires/tranny/rear end.

Here's the thread

 

[IwantMKIII]

3.91LSD. I have a gauge cluster if you need one cheap

 

[Nocheez]

Won't it just be easier to swap in my 3.73 gear from my auto? I mean, supposing that's feasible.

 

[foreverpsycotic]

A cluster is such an easier swap, and idk if the auto gear will fit in an r154, doubt it though. Besides, pre 89 clusters > post 89 clusters.

 

[Justin]

It's not worth it when it'll cost twice the price of the ticket in gas to drive up to fight it, plus the lost time at work.

You can contest a ticket by mail. If you write a really good letter and explain what's going on you have a good chance of it getting thrown out.

My dad went from cali to oregon where the speed drops from something like 70 to 55. His cruise wasn't working in the supra and he just went right on through around 78-80. Got a ticket for it. Wrote a letter and sent in a check. Must have been a damn good letter cuz he got the check back in the mail a few weeks later

 

[JonoTurbo]

Swapping the cluster will have no effect on speedometer accuracy. There is a small adjuster in the speedo for fine tuning but I doubt it will correct that much.

Your only choice is to change the ratio on the cable by swapping the gear out or using some sort of adapter.

 

[CRE]

Jono's right, the speedo can be adjusted to about +/-15%. This doesn't correct the odometer or trip meters though. If you can't source the correct speedo drive gear then an intermediary gear box is the best way to go.

 

[Nocheez]

I have my gear from the automatic in my garage, can anyone confirm if it is the same or not for an R154?

 

[Dan_Gyoba]

It seems that your R154 came from an older turbo with a 3.909:1 differential in it, but that doesn't account for the full difference.

The difference between a 3.73 and a 3.91 only accounts for about 5% Tire size accounts for another 3.2% (225/50R16 diameter=631.4mm, 274/40R17 diameter=651.8mm)

I calculate that if your odometer/speedometer were working correctly to start with, you should be going about 8.2% faster than your indicated speed.

That is, assuming that your R154 had an appropriate gear for a 3.909:1 differential, AND that there aren't differences in the number of rev/mile for the speedos.

I have a transmission from an '87T in my '89NA. My '89NA is an early '89, so has more in common with the '88 than the '90.

The speedo in the '87T was rated for (IIRC) 1025rev/mile. My '89NA speedo was rated in km, however, it was rated at 637rev/kilometer, which is so close that it might as well be the same.

If you take out your gauge cluster, the speedo face will list how many revs/mile your speedo is callibrated for. (Or more accurately, your odometer. Your speedometer is roughly based off of that.

 

[tissimo]

The trans out of my 91s had different gears then the 89s i've seen. The 89s were like 31/10 adn my 91s were 33/11 or something.. I dont know the exact numbers but I tried to put my 91 speedo gear in my 89 transmission (since hte 89s was off) and it was still off..

 

[MassSupra89]

Funny, I left Charlotte yesterday with the opposite problem. My speedo would be reading 5mph faster than my GPS.

 

[Nocheez]

It seems that your R154 came from an older turbo with a 3.909:1 differential in it, but that doesn't account for the full difference.

The difference between a 3.73 and a 3.91 only accounts for about 5% Tire size accounts for another 3.2% (225/50R16 diameter=631.4mm, 274/40R17 diameter=651.8mm)

I calculate that if your odometer/speedometer were working correctly to start with, you should be going about 8.2% faster than your indicated speed.

That is, assuming that your R154 had an appropriate gear for a 3.909:1 differential, AND that there aren't differences in the number of rev/mile for the speedos.

I have a transmission from an '87T in my '89NA. My '89NA is an early '89, so has more in common with the '88 than the '90.

The speedo in the '87T was rated for (IIRC) 1025rev/mile. My '89NA speedo was rated in km, however, it was rated at 637rev/kilometer, which is so close that it might as well be the same.

If you take out your gauge cluster, the speedo face will list how many revs/mile your speedo is callibrated for. (Or more accurately, your odometer. Your speedometer is roughly based off of that.

Good information, thank you. I wonder if I did the math backwards. I divided 273 by 243, but maybe I should have done it the other way around. That's still like 10.xxx difference, though.

Maybe my speedometer was already off slightly? And all these factors combined means I need to get this shit fixed the right way

Funny, I left Charlotte yesterday with the opposite problem. My speedo would be reading 5mph slower than my GPS.

No, we're having the same problem I think. My speedo is slower than my actual speed.

 

[Zumtizzle]

the gears are not the same but cost 5 bux from toyota!

 

[Who]

It's not worth it when it'll cost twice the price of the ticket in gas to drive up to fight it, plus the lost time at work.

I don't know squat about cars but I know about speeding tickets. Get yourself a traffic ticket attorney. Search the yellow pages in your area or the area where you got the ticket. They do all the legwork and you lose no time from work. Somehow they beat the ticket 65% of the time or get it reduced with no points.

 

[noah89t]

My dad went from cali to oregon where the speed drops from something like 70 to 55. His cruise wasn't working in the supra and he just went right on through around 78-80. Got a ticket for it. Wrote a letter and sent in a check. Must have been a damn good letter cuz he got the check back in the mail a few weeks later

or maybe the state where he got the ticket doesn't accept out of state checks. 2 days ago my mom called me saying that a letter showed up there from some county in miss. so i had her open it over the phone and it said i had an unpaid ticket from 12-03-02!!!! wtf, it was 6-25-08 when she told me. well i paid that ticket with a personal check and my bank is in louisiana. they sent it back to me a few weeks later so i said fuck them, if they are too fuckin dumb to cash an out of state check, then they must not have computers yet to document any of this. Now today, i am fighting with those idiots about a 6 year old ticket.

i would let your dad know to check up on that ticket in a month or so.

 

[tsuper92]

you will need to change the gear on your output shaft of your r154,along with the small plastic gear.i don't believe the auto speedo gear's work on the r154. i never actually checked the gear on the auto output shaft though.this is just going off the piece that un-bolt's from the trans.

 

[MassSupra89]

My mistake, faster* The speedo would say 80 or alittle over when I was doing 75 on the GPS.