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After having just completed the HVDA transmission conversion, I now need my speedo recalibrated.
Is it possible to do myself? Any instructions out there?
Is it possible to do myself? Any instructions out there?
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Speedo recalibration... can it be done?
- Thread starter Gliderman8
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Geo Hahn
Yoda
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Depending on how much it is off, yes you can do something yourself. This site gets into the inner workings of the mechanical speedometer:
https://home.comcast.net/~rhodes/speedo.html
Note: this adjustment only changes the speed shown, no affect on the odo's.
Simply stated, you open up the unit and adjust the calibration by keeping the drag cup from moving while you reposition the needle. Crude but effective, especially if you are dealing with a small error.
One problem is that the change you make this way is not linear... i.e. you can adjust the unit to read exactly 60 when you're doing 60 but above and below that there may still be some error.
The actual process has you temporarily putting the unit into operation, driving with a reliable GPS, checking for the error at various speeds, pulling over and moving the needle a bit, rinse, repeat.
The results will not be perfect but possibly 'good enough'.
I have done this procedure to adjust for changes in tire size, aging hair spring and general inaccuracy of the unit and have got mine pretty good through the 30 - 70 mph range.
A proper shop will change the internal gearing so the odometers are correct. There may also be conversion units available (cable in, cable out) that change the ratio to a correct one for the stock speedo.
https://home.comcast.net/~rhodes/speedo.html
Note: this adjustment only changes the speed shown, no affect on the odo's.
Simply stated, you open up the unit and adjust the calibration by keeping the drag cup from moving while you reposition the needle. Crude but effective, especially if you are dealing with a small error.
One problem is that the change you make this way is not linear... i.e. you can adjust the unit to read exactly 60 when you're doing 60 but above and below that there may still be some error.
The actual process has you temporarily putting the unit into operation, driving with a reliable GPS, checking for the error at various speeds, pulling over and moving the needle a bit, rinse, repeat.
The results will not be perfect but possibly 'good enough'.
I have done this procedure to adjust for changes in tire size, aging hair spring and general inaccuracy of the unit and have got mine pretty good through the 30 - 70 mph range.
A proper shop will change the internal gearing so the odometers are correct. There may also be conversion units available (cable in, cable out) that change the ratio to a correct one for the stock speedo.
OP
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George-
I did happen to come across that website last night and bookmarked it. You are right... after reading the instructions, I also thought it was a crude method.
What about these conversion units that go between the transmission and the speedo... are they any good?
I am starting to think about them rather than send the speedo in for surgery. What do you think?
I did happen to come across that website last night and bookmarked it. You are right... after reading the instructions, I also thought it was a crude method.
What about these conversion units that go between the transmission and the speedo... are they any good?
I am starting to think about them rather than send the speedo in for surgery. What do you think?
TR3driver
Great Pumpkin - R.I.P
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None of the shops I talked to had the materials to change the odometer gearing. The only option they offered was a "ratio adapter", which is apparently a fairly common item with the 4x4 crowd.
Seems odd to me that Herman doesn't include the adapter with the conversion kit.
Seems odd to me that Herman doesn't include the adapter with the conversion kit.
OP
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When I bought my toyota trans the speedo gear was missing. I assume they just unscrewed the the drive gear plug and pulled the transmission out of the donor car.
When I went to toyota to buy the speedo gear for the tail-end of the transmission I learned that there were at least three different gears used in that transmission.
I would think that would make it difficult for Herman to stock different ratio adaptors.
I've gotten prices of $175 to change out the gears in the speedo, and a price of $60 - $80 from my local speedo shop to supply a ratio adaptor. Right now I'm leaning towards the adaptor, not only for the price, but it leaves the original speedo unchanged incase someone in the future wanted to put the original trans back into the car.
I need to first check the indicated vs the actual speed with a gps to see how much it may be off.
When I went to toyota to buy the speedo gear for the tail-end of the transmission I learned that there were at least three different gears used in that transmission.
I would think that would make it difficult for Herman to stock different ratio adaptors.
I've gotten prices of $175 to change out the gears in the speedo, and a price of $60 - $80 from my local speedo shop to supply a ratio adaptor. Right now I'm leaning towards the adaptor, not only for the price, but it leaves the original speedo unchanged incase someone in the future wanted to put the original trans back into the car.
I need to first check the indicated vs the actual speed with a gps to see how much it may be off.
dklawson
Yoda
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As a footnote to my earlier post about the ratio box and Elliot's prices quoted above... you will likely (or should) supply the speedo shop with two (2) new speedo cables at the same time. One will be the cable for your car's speedometer, the other will be the one for your car's transmission (assuming they are of different makes). They cut the ends off of both and put the "correct" ends on them to connect to the ratio box.
The $80 for a ratio box sounds really good (probably better than APT can offer) but don't forget to add in the cost of the new cables. You'll also have to "dry fit" the cables to your car to mark where you want the ratio box to end up. You may want to bolt it to the frame somewhere that is both protected and accessible.
As for how reliable they are, I ran one on our GT6 for a year or so without issue. My father-in-law had put a different rear end in the car for the track so we had to match that setup's turns/mile. When we finally put the correct differential back in we removed the ratio box and went back to a standard cable.
The $80 for a ratio box sounds really good (probably better than APT can offer) but don't forget to add in the cost of the new cables. You'll also have to "dry fit" the cables to your car to mark where you want the ratio box to end up. You may want to bolt it to the frame somewhere that is both protected and accessible.
As for how reliable they are, I ran one on our GT6 for a year or so without issue. My father-in-law had put a different rear end in the car for the track so we had to match that setup's turns/mile. When we finally put the correct differential back in we removed the ratio box and went back to a standard cable.
TR3driver
Great Pumpkin - R.I.P
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The folks I talked to only wanted one cable, that fit my car at both ends. As you say, they would cut it apart and insert the box in the middle. I believe Herman's kit comes with a custom-made cable that mates the Toy box to the Triumph speedo.dklawson said:
The fellow I talked to said their box could be adapted to the cable, so another option might be to use a standard Toy cable on one side, and a standard TR cable on the other. Might be nice if you ever have to replace the cable.
martx-5
Yoda
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As a side light here, I have the Toyota 5-speed conversion also...Herman's...I also put 185/70 tires on my car, so I figured that my speedo would be way off, what with the tranny and tire size change. I took my GPS (Garmin) with me one outing to find out how far off the speedo was. Well, at 30mph it was dead on. At 40, 50, 60, 70 & 80mph, it was still dead on. I'm guessing that whatever speed differential the Toyota trans made, was offset by the tire size.
Sometimes you just get lucky...
Edit: Now that I think about it, just how far off is the speedo?? Did you go through Herman's procedure to figure out how far it's off, or are you just assuming it can't be close. The easiest way to see is to do it like I did...with a GPS. Maybe it's not very far off. A couple of miles per hour should be livable.
Sometimes you just get lucky...
Edit: Now that I think about it, just how far off is the speedo?? Did you go through Herman's procedure to figure out how far it's off, or are you just assuming it can't be close. The easiest way to see is to do it like I did...with a GPS. Maybe it's not very far off. A couple of miles per hour should be livable.
BobbyD
Jedi Knight
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Elliot.........I also have the HVDA conversion and Goodparts Nissan diff conversion and different sized tires so my speedo was way off.......as was the odometer. The process for collecting the data a repair shop needs is documented on my site as well as a link the a pdf file on how to rebuild and calibrate it yourself..... if you were so inclined. I, however, on Herman's recommendation called Morris at West Valley Instrument which specializes in just British gauges. Morris quoted a price and an interval based on everything being in the condition I stated. After getting speedo, he called me back, confirmed the price and time frame and had it all returned to me with 10 days. I didn't see any sense in just having the speed being calibrated so I also had him change out the odometer gearing so that would be correct too. Since then I've also sent him my tach to calibrate. As an aside, Morris is a stickler on the cable tip being properly sized and asked that the cable be shipped with the gauge. He rebuilt both my Speedo and Tach gauge to spec (the specs are also on my site at the above link). If the tip is over or under sized it can mess up the gauge guts in a short time. I shared the cable info with Herman who confirmed the specs with Morris and found out that the cables he was shipping with the 5 speed conversion were out of spec. He ended up having them all rebuilt.
And lastly Paul Rego just had Morris rebuild all of his gauges and has it all documented on his site.
And lastly Paul Rego just had Morris rebuild all of his gauges and has it all documented on his site.
OP
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Thanks everyone for all the good info you have given me. I will check out West Valley as well as check your site Bobby... thanks!
The local speedo shop showed me one of the ratio adaptor that they build; it attaches directly to the toyota trans. The box has the correct fitting that mates it to the toyota so there is no need for two cables. Then its just a matter of running the cable from the box to the speedo.
Art- you are correct.... first I need to check (with a gps) the actual vs. the indicated speed. I'm running 205/70 tires with the toyota trans.
The local speedo shop showed me one of the ratio adaptor that they build; it attaches directly to the toyota trans. The box has the correct fitting that mates it to the toyota so there is no need for two cables. Then its just a matter of running the cable from the box to the speedo.
Art- you are correct.... first I need to check (with a gps) the actual vs. the indicated speed. I'm running 205/70 tires with the toyota trans.