Speedometer gear connection&operation (early versus later)

[moore_rb]

HELP! My Patrol's speedometer doesn't work !


Faux40 did a great pictoral guide on how to refurbish your speedo guage (great if you ignore the pseudo-criminal odometer tampering, that is ):

http://www.60patrol.com/forum/viewtopic.php?f=23&t=2978

And there is another thread with great info about troubleshooting an inoperative speedo here:

http://www.60patrol.com/forum/viewtopic.php?f=4&t=2206

But there is another important aspect of the Patrol's speedometer operation, and that is the model year (and design) of your transfer case.

There is a difference in the design of the speedo output gear on early Patrol transfer cases, versus later style transfer cases; and this difference changes the behavior of the speedometer cable's operation.

On the early style TCases (seems like early 66 and older Tcases, which were most often painted Seafoam green from the factory), the location where the speedo cable connects to the speedo gear is on the front driveshaft output yoke near the two shifter rods, and the cable connects from over the top:

CAM00583.jpg

With this above style of speedo gear, the only way to spin the speedo cable is for the front driveshaft yoke to be turning. On early Patrols that had factory flanges on the front hubs, this was not an issue, because the flanged hubs would force the driveshaft to turn, which would spin the speedo gear (so even when the TCase was shifted to 2WD, the front driveshaft and speedo gear would still turn due to the hub flanges)

If you install free-wheeling locking hubs on a Patrol that has this early style TCase and speedo gear orientation, then the following test behaviors will be observed; assuming everything else (speedo guage, cable, etc) is in normal working order: I have confirmed all of these test conditions below using my green El Paso Patrol, which runs Warn hubs, and one of these early style TCases (from '63) and has this early style speedo gear connection:

1) When front hubs are unlocked and TCase shifted to 2wd = No front driveshaft turning, no speedo gear turning, no speedometer.
2) When front hubs are locked (or stock front flanges used instead of locking hubs) and TCase shifted to 2wd = Front driveshaft turning, speedo gear turning, speedometer works.
3) When front hubs are unlocked and Tcase shifted to 4wd= Front driveshaft turning, speedo gear turning, speedometer works.
4) When front hubs are locked, and TCase shifted to 4wd= REAL 4WD, front driveshaft turning, speedo gear turning, speedometer works.


Now, with the later style TCase (seems like mid 66- later, and more often associated with Blue transfer cases), the speedo gear comes off the BOTTOM of the front TCase output cone:

CAM00584.jpg

This is the best photo I have of this style, but right now the speedo gear is uninstalled (it's soaking in degreaser at the moment )

Now, with this later style of TCase, the speedo gear is supposed to turn regardless of whether the front driveshaft is turning or not- So you can use locking hubs, 2wd, 4wd, etc, and the speedo cable should spin regardless. I have not been able to personally verify this behavior because this Patrol is still not yet road ready (I will verify it someday ), but I remember reading where RMPO had posted a lot of technical detail about these two different speedo gear styles in the ExPo thread about the 64 that he is restoring for his customer:

http://www.expeditionportal.com/forum/t ... ost1515481


So, in summary- If you want to use locking front hubs AND maintain normal speedo operation in 2wd/hubs unlocked mode, then a mid 66-later style (probably blue) transfer case is probably a better option for you...

[RiverPatrol]

Now that's what I'm talking' about.

The first scenario is where it gets a little confusing, though. I know that very early Patrols, '62s for instance, the speedo would not work unless it was in 4wd or had the hubs locked. One poor guy bought a new speedo and cable before he figured this out. But around '63 or '64 something changed to enable the speedo to work in 2wd with freewheeling hubs. The thread on Expedition Portal touches on it slightly, but does not provide a solid conclusion.

I used to have 4 engines with trannies sitting on the ground side by side that I could see these differences, but those got scrapped a while ago. And, all of my parts books are in storage right now so I can't do the research. But, I do know that the change from running off the top of the transfer to the bottom happened in '66. Also, '64 and '65 Patrols' speedos worked fine in 2wd and freewheeling, but I'm not sure what the change was or when it was implemented.

This would mean that the low mileage reading on an early Patrol would be very suspect. If the speedo, and subsequently odo, only worked with the hubs locked or in 4wd, the mileage recorded would not include any miles driven with the front hubs unlocked in 2wd, which would be your highway miles. The mileage recorded would only be miles that the truck was driven in 4wd and/or with the hubs locked. This is only on vehicle with freewheeling hubs, of course.

[50car]

Here is the 68/69 that I call Montana Patrol. It was painted in the seafoam green and is attached to a blue transmission... Was there a transition time where the eariest of the later style were still painted the seafoam green? hmmm...

speedometer cable attachment location.jpg

[moore_rb]

This would mean that the low mileage reading on an early Patrol would be very suspect. If the speedo, and subsequently odo, only worked with the hubs locked or in 4wd, the mileage recorded would not include any miles driven with the front hubs unlocked in 2wd, which would be your highway miles. The mileage recorded would only be miles that the truck was driven in 4wd and/or with the hubs locked. This is only on vehicle with freewheeling hubs, of course.

I concur. On any early Patrol where the speedo is taken from the front driveshaft output flange, and had the front hubs converted from the factory flanges to locking hubs, the odo would only be ticking if the hubs were locked, or if the TCase was in 4wd mode....

. Also, '64 and '65 Patrols' speedos worked fine in 2wd and freewheeling, but I'm not sure what the change was or when it was implemented.

Hmmm... so maybe you are right, and there WERE 3 alternative speedo connection points on the US market Patrols... which also wouldn't surprise me (you being right, I mean )

So, I went back and re-read the Expo post again, and Ian also mentions some 64's/65's having the speedo gear taken from the rear output on the TCase... which would allow the speedo to turn when the hubs were unlocked.

So, both the "Patrol Uber-Gurus" seem to agree on this point... Which probably makes it a proven fact.

Was there a transition time where the earliest of the later style were still painted the seafoam green? hmmm...

On the question of color - I've got no opinion (Wait, was that moore_rb that just wrote that...? )

I dug around, called around, read everything I could, and scrounged every picture I could get my hands on about engine, transmission/TCase color combinations that Nissan used with the Patrol, and the best information I have says Nissan had absolutely NO guidelines about the color(s) they painted drivetrain parts...

That's why in my original post at the top of this thread, I made sure to write "most often green", and "probably blue" - I just know Esteban will read this and post "What about black transmissions and transfer cases... ???? "

Jeff-- I would think that since you have two of these 68/early69 Patrols that both have the same blue trans with green Tcase combos, that the color scheme is probably correct for your rigs...

But your speedo cable location suggests that you won't have to worry about your speedo working- even if you use locking hubs

[Esteban]

Good information Robert. Always fun to learn something about the Patrol.

Mine is a 65 and has the speedo connection at the same place as later Patrols. Maybe they shipped the improved version to other markets before the USA.

[moore_rb]

. Also, '64 and '65 Patrols' speedos worked fine in 2wd and freewheeling, but I'm not sure what the change was or when it was implemented.

Hmmm... so maybe you are right, and there WERE 3 alternative speedo connection points on the US market Patrols... which also wouldn't surprise me (you being right, I mean )

So, I went back and re-read the Expo post again, and Ian also mentions some 64's/65's having the speedo gear taken from the rear output on the TCase... which would allow the speedo to turn when the hubs were unlocked.

So, both the "Patrol Uber-Gurus" seem to agree on this point... Which probably makes it a proven fact.

OK... Here we go - Thanks to the White 65 Colorado Patrol, we now how have photographic examples of all three original Nissan speedometer configurations.

Version one is the example I posted earlier from the very early (62-63, maybe early 64's) transfer cases, where the speedo gear is on the front output shaft of the transfer case - If you have the speedo cable hookup in this location, then your speedometer will not operate when the hubs are unlocked and the shifter is in 2wd mode. The front driveshaft HAS to be turning for the speedometer to turn:



The 2nd style is the one that the Patrol Gurus pointed out, that seems to have come along sometime in 64-65. Nissan plugged the original speedo output with a plastic plug:



Then they used a new style rear output flange (made of Aluminum, as RMPO pointed out in his expo thread) that had the speedo hookup taken from the rear output shaft.



With this style of speedo hookup, the speedo cable will turn whenever the rear driveshaft is turning, so unlocked front hubs, and 2wd mode will still allow the speedometer to operate normally.

The last style is the one we also covered above- This style came along somewhere in 65-66-ish, and the speedo gear is on the bottom of the t-case, taken off the secondary driven shaft:



This style will operate just like the intermediate 64-65 style above - when the rear driveshaft is turning, so should the speedometer.

[RiverPatrol]

Finally, the missing link! Thank you.

Wow, you could plant a crop of corn on that second transfer.

[moore_rb]

Wow, you could plant a crop of corn on that second transfer.

Yeah, now I know why I got such horrible fuel economy towing that white Patrol home from your place... I was dragging 50 years (and 5000 pounds) worth of Colorado mud home with it.

Just wait until you see how the frame from that Patrol looks now . I'm almost ready to post some pics...

[RMP&O]

Really well written and put together Rob! Great pics and great explanation.

I am of the opinion that the early style be it the front or rear locations for speedo pinion are a weak and not very good design. The gear that drives the speedo pinion on the early style is simply a crush sleeve type design. Meaning, the gear has no splines on the inside. It is simply smashed down by the output spacer and nut. Any slop, play or wear in the gear and it will trash the speedo pinion fast. Every one of these I have seen, at the least, the teeth on the pinion are worn down badly. The newer design which is pulled from the back of the nose cone on the t-case is a major upgrade and improvement by Nissan. The gear for the speedo pinion is bigger and beefier and it has splines on the inside which ride on a shaft. Everyone of these I have seen is in relatively good condition. You can upgrade your old t-case to the newer design speedo pinion but unfortunately to do that you have to change the whole t-case out. The nose cone is completely different as well as the guts in the nose cone, they do not interchange.

Also to add to this, there are two types of speedos. An early and a late style. I believe the early style came on Patrols up to 65 but 64 could have been the end of it. On the back of the speedo is a different connection for the speedo cable. They do not interchange. You can still get the later style speedo cable in aftermarket form in Australia but the early style speedo cable is NLA.

Cheers

[RMP&O]

Here is the 68/69 that I call Montana Patrol. It was painted in the seafoam green and is attached to a blue transmission... Was there a transition time where the eariest of the later style were still painted the seafoam green? hmmm...

Just one of many oddities on these trucks. On the dark blue cases, inside it is painted the seafoam green too. So it is almost like they used the seafoam as a primer and sprayed over it with the dark blue. I also have a 68 & 69 trans & t-case here with the dark blue on the trans and the seafoam on the t-case.

Strange indeed.

Cheers