The only other really accurate way , other than a smart phone or gps unit is to have a converter box installed . There are a few shops out there that will build them , at a cost , of course .
Sarge
Sarge
Speedo Correction (1 Viewer)
- Thread starter cxh10
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
I personally listen to the pitch of the whistle thats created from worn out weatherstripping on my 40. Im good to go as long as I don't go deaf.
Updating this thread a bit with more info/tech.
I had a leak from the speedometer driven gear location so when the truck was restored I replaced the whole assembly. The speedometer driven gear assembly kits are still in stock here in the region. I don't know what was in there before (I think a 6x16 or 6x17) but I replaced it with a 6x17. I think that was wrong.
So with the 32" tires I have now (an increase from the 30's I had before) along with the 6x17 speedometer driven gear and 3.70 differentials I have the following discrepancies:
Speedometer:GPS Actual
60 kph : 74 kph
80 kph : 95.8 kph
90 kph : 109.4 kph
I gathered the GPS actual by driving 5km with the speedometer on the given value as consistently as possible... then I took the average speed of the saved track.
So a 21-23% difference. That's significant.
I've ordered both the 6x16 and the 6x15 speedometer driven gear kits. I'll probably try the 15 first.
As I've read through the documentation in this thread from @IDave as well as in TOYODIY, it seems that the 6x17 drive gear on the output shaft will work with the 15, 16, and 17 driven gears.
I'll post back with my results.
I had a leak from the speedometer driven gear location so when the truck was restored I replaced the whole assembly. The speedometer driven gear assembly kits are still in stock here in the region. I don't know what was in there before (I think a 6x16 or 6x17) but I replaced it with a 6x17. I think that was wrong.
So with the 32" tires I have now (an increase from the 30's I had before) along with the 6x17 speedometer driven gear and 3.70 differentials I have the following discrepancies:
Speedometer:GPS Actual
60 kph : 74 kph
80 kph : 95.8 kph
90 kph : 109.4 kph
I gathered the GPS actual by driving 5km with the speedometer on the given value as consistently as possible... then I took the average speed of the saved track.
So a 21-23% difference. That's significant.
I've ordered both the 6x16 and the 6x15 speedometer driven gear kits. I'll probably try the 15 first.
As I've read through the documentation in this thread from @IDave as well as in TOYODIY, it seems that the 6x17 drive gear on the output shaft will work with the 15, 16, and 17 driven gears.
I'll post back with my results.
Looking forward to your results. A friend recently visited and we checked via watch and GPS and came up with about 12%. The radar signs on the highway being pretty accurate. So where I hold 60mph it takes 65 seconds to go a mile. I should be recording 100 kph and the highway signs show me at 78kph. I note that the AutoMeter speedometer is calibrated at 1,000 rpm equals 60 mph. The old '70 model was calibrated that way but the '79 is 1,025 at 60. So I think the easier fix for me is taller tires in the future. Regardless, when I was rolling across the basin going to the coast and running close to 70 mph indicated, the rig feels twitchy.
pbgbottle
Forum Lifer
Post pic of gears also please,
I have never seen the 15 tooth gear. Cool thanks. I need to change mine also.
I have never seen the 15 tooth gear. Cool thanks. I need to change mine also.
I got the gears... still haven't swapped.
Some pics of the gears.
Here they are, side by side.
This one is the 6x15
This one is the 6x16
Not noticeably different.
Are these really NLA in the States? I could bring some back with me in late March when I visit the States.
Thanks for the pics with part numbers. Not sure what I need to do with my '79 which has AutoMeter gauges. The old speedo unit said 1,025 RPM for 60 mph and my AutoMeter is 1,000 rpm for 60. However, I'm at least 19% off vs highway speed lasers and GPS. So I'll have to do a combination of things both inside the transfer case as well as the driven gear and possibly tires!?! The tires I'm running are very close to the diameter listed for 7.00 - 15's. At least I don't have to worry about getting speeding tickets
.
.
pbgbottle
Forum Lifer
Thanks for the update. I still want to try a 15 also. Don't take them all down to the U.S. Lol
I need to order one ,,
I need to order one ,,
If you do not have the matching drive gear on the output shaft of the transfer case to drive the 'driven' gear pictured above, it will ruin the driven gear...
6x15 needs the corresponding 6x15 gear
6x16 needs the corresponding 6x16 gear
6x17 needs the corresponding 6x17 gear
6x15 needs the corresponding 6x15 gear
6x16 needs the corresponding 6x16 gear
6x17 needs the corresponding 6x17 gear
Downey
SILVER Star
I'm too old and tired to get my head back into all of this. In the old days (when everyone was buying 33" tall tires) we merely installed 4.88 gears, which bought back the power lost, and corrected the spedo- - -but mpg still sucked.
If you do not have the matching drive gear on the output shaft of the transfer case to drive the 'driven' gear pictured above, it will ruin the driven gear...
6x15 needs the corresponding 6x15 gear
6x16 needs the corresponding 6x16 gear
6x17 needs the corresponding 6x17 gear
There's only two drive gears... 33481-60030 and 33481-60020.
For the 6x15, 6x16, and 6x17 you need 33481-60030.
For the 6x18 you need 33481-60020.
So if you already have a 15, 16, 17 you can assume you have 33481-60030 installed in your transfer case already... and therefore you can swap between the three driven gear accordingly.
Can anyone corroborate or poke an obvious hole in my read on this.
What's the process to switch these gears?
1911
chupacabra
No, you're not wrong. US 40 models from 1979 - on came with 3.70 diffs. I own one.
Yes I have 33's on my '78 and when the speedo reads 50 I am actually going 60 according to friend with new Runner and original tires next to me. Stock 4:11 gearing as well on my '78. BFG KO2's 33X10.5X15 FWIW
nogo
SILVER Star
Do the 1979 and later US variants of the 40 series run the split case transfer as standard equipment ?
1981-1983 has the split case. 1979-1980 still has the older transfer case with the drum brake in the US.
1911
chupacabra
1981 and later had the split case; '79 and '80 still had the old(er) case with the hand brake on the output shaft.
EDIT: SW20 beat me to it!
