Speedometer

Joined
Dec 9, 2003
Messages
22
Is there a way to recalibrate a speedo on a 40 so that it reads accurately with oversize tires? I don't want to change the gearing in the diffs or anything.
 

Poser

Oh...Durka Durka Durka.
Supporting Vendor
Joined
Oct 1, 2003
Messages
20,465
Location
MN
Since majority of the Land Cruisers that were imported into the USA came with an H78-15 or equivelant, hows about you give us the info on what tire size you call oversized, and then we may be able to help you, as there are more than one spedo gear for the t-case available...

Good luck!

-Steve
 
Joined
Dec 9, 2003
Messages
22
I pick up the vehicle this weekend, I think it's running 31s or 32s.
 

Romer

fatherofdaughterofromer
Moderator
Joined
Sep 14, 2003
Messages
11,738
Location
Centennial, Colorado
Go to the following link:
http://www.tlca.org/trails/techxchg/rpmtbls/index.html

this tells you the difference in RPM. You can post what the specifics are about your cruiser and I am sure some one can tell you what stock tires were and the diff you have. You then look up the new tires and take a ratio of the difference.

For example if you have a 4.11 diff and the stock tires were 28", then the RPM at 60MPH would be 2960. If you now have 31 inch tires, at an RPM of approx 2960 you would be going about 68 MPH. The RPM is the constant.

As a general ROUGH rule of thumb for Highway miles (4th gear) you can take the ratio of 68/60= 1.13 and multiply it by whatever speed you are going. Best to make a little table.

For example, if your speedometer says 50 you are probably going 56 MPH

Again, You need to define what the vehicle had as stock tires and what your diff is to come up with this.

Someone please check me on my math.

ken
 
Joined
Oct 31, 2002
Messages
1,501
Location
Kennett Square
These guys work miracles on some old british crap...they may be worth a call.

http://www.nisonger.com/

Or you can do what I and others now doubt do...buy an inexpensive little tach, go to the tcla tables, and make little paint marks at the appropriate rev/speed combos.
 
Joined
Jan 3, 2003
Messages
7,184
Location
McCall, ID
If you look at the speedometer gears for the housing behind the transfer case on the SOR site, you will find that they offer several different sizes/ratios to fit. I have wondered if that is what they are for (different tire sizes). I would give them a call.
 
Joined
Mar 27, 2003
Messages
6,364
Location
Georgia Tech
Get a GPS. Thats what I did, my speedo is WAY off, and now I always know how fast, regardless of tire size, diff gearing.
Not to mention I will never get lost again. :D
 

cruiseroutfit

Supporting Vendor
Moderator
Joined
Jan 9, 2003
Messages
11,050
Location
Utah
Website
cruiseroutfitters.com
I'm a big fan of the stock Dash Cluster, but if you must have a correct speedo, get an aftermarket one (VDO, Autometer, etc) they use a speed sensor on the t-case that can be adjusted using milemarkers to get your speed 100%...

Mine is actually quite close... 4.56/Splitcase/35's
 

devo

SILVER Star
Joined
Nov 3, 2002
Messages
2,399
Location
City Different
When I went to 33's and 4:88's on my 60 the speedo was way off. A trip to my local speedo shop and $70.00 later I'm within 0.1 mile/ 10mls traveled. They have a gearing piece that goes between the transfer case and the speedo cable that fits very well.
Delux Speedometer 303 629 6958 Denver,Co.
devo
 
Joined
Jan 3, 2003
Messages
7,184
Location
McCall, ID
That's what SOR sells, I think.
 

Users who are viewing this thread

Top Bottom