CDL Switch Only???

[Bryan E.]

I just installed the CDL switch, and am going to do the Pin 7 Mod also. I read that people used to unplug a wire on the transfer case before Dan figured out the P-7 mod. My question is...why do you need to do one of these or the other? I know the P7 mod is the way to go, but I'm JUST curious what happens if you just use the switch, but nothing else? Does it not work right with switching it off, without the wiring mods? Please explain this history to me. I've done research and didn't find anything on why it all got started.

Thanks,

 

[Rookie2]

Without doing the Pin 7 mod, you can not run in 4-lo without the center diff automatically locking, regardless if you have the CDL switch. What Pin 7 does is breaks the signal between the shifter and the transfer case, so when you select 4-lo, it doesn't automatically lock the center diff. So now if you want to lock in 4-lo (or 4-hi for that matter), you use the switch.


Rookie2

 

[speyrod]

I believe it also changes the shift points as the ECU doesn't know it's in low.

 

[Bryan E.]

What are the advantages to either mod??

Ok, so here's where my question arose. I was reading the instructions in our Tech Link's that Cruiser Dan, Wrench, and Rogue are explaining how to do this Pin 7 mod. . . . . . Rogue "The center diff lock switch is only the first step to achieving an unlocked center diff in low range. You will then have to either remove a plug directly from the t-case, or do some modifications to your wiring. Both options have their up's and down's." . . . . So my question is... What would be the advantage of the transfer case wire unpluged over the Pin 7 mod? If I understand the info correctly, the Pin 7 mod gives a more desired shift points, holding in gears longer until you let off the gas and then it downshifts quicker. Is there more to this story than this?? I guess they first figured out how to disconect the wire at T-case, then later discovered the Pin 7 mod and it's better, so now everyone just does that?? Rogue's saying that each mod had's it's up's and down's made me wonder what the up's were to just the t-case wire unplug mod. Sorry for my lame questions, but maybe I'm not the only one to wonder this.

 

[Aussie cruiser]

Why don't the US cruisers have the CDL switch fitted ?.All Australian cruisers have them fitted except the Base models which are part timers and those with the Viscous copling fitted instead

 

[cruiserdan]

Why don't the US cruisers have the CDL switch fitted ?.All Australian cruisers have them fitted except the Base models which are part timers and those with the Viscous copling fitted instead

The ones without ABS had the switch fitted.

 

[cruiserdan]

Ok, so here's where my question arose. I was reading the instructions in our Tech Link's that Cruiser Dan, Wrench, and Rogue are explaining how to do this Pin 7 mod. . . . . . Rogue "The center diff lock switch is only the first step to achieving an unlocked center diff in low range. You will then have to either remove a plug directly from the t-case, or do some modifications to your wiring. Both options have their up's and down's." . . . . So my question is... What would be the advantage of the transfer case wire unpluged over the Pin 7 mod? If I understand the info correctly, the Pin 7 mod gives a more desired shift points, holding in gears longer until you let off the gas and then it downshifts quicker. Is there more to this story than this?? I guess they first figured out how to disconect the wire at T-case, then later discovered the Pin 7 mod and it's better, so now everyone just does that?? Rogue's saying that each mod had's it's up's and down's made me wonder what the up's were to just the t-case wire unplug mod. Sorry for my lame questions, but maybe I'm not the only one to wonder this.

The "up" for un-plugging the low4 postion switch is it is easier to do than breaking into the kick panel. Before I revealed "pin7" that is how everybody did it.

 

[Bryan E.]

Ok Dan, that makes sense to me. Thanks for the info on doing this mod, as well as selling me the actual part. Took about 10 min. to install the switch. I'll do the the Pin 7 mod tomorrow.

Thanks to all for the info.

 

[RavenTai]

I believe it also changes the shift points as the ECU doesn't know it's in low.

You only get into shift points when you unplug the connector on the transfer case, the 4-Lo signal goes to the ECU/TCM via pin 9 or 19 depending on year. Shift points are not affected by pin presence or removal of 7. The pin 7 mod only kills the 4-Lo signal to the CDL control relay preventing automatic locking of the CDL.

Having 4-lo without a locked center is nice, you only want locking of any of the diffs when you actually need it.

 

[OZCAL]

Why don't the US cruisers have the CDL switch fitted ?.All Australian cruisers have them fitted except the Base models which are part timers and those with the Viscous copling fitted instead

I'd imagine the vast majority of original U.S. 80 buyers nodded vaguely when the salesman explained low range and the locking differential, then forgot about the feature entirely. It is entirely common for differential locks (center, front and rear) to "gum up" and fail to activate from years of benign neglect on the part of the original owner.

I suspect there is also an insurance rating concern, as the cdl switch turns off the ABS when activated. ABS is a feature that usually provides a discount with insurors.

 

[Fochdog]

I just added my CDL with "Pin 7" last week. I finally got to use it this past weekend. It was very nice in some tight wooded areas.

In full open mode and low range I was turning tighter than an FJ40 with a locked t-case and spool rear axle. Not a big surprise but very cool!

 

[elmariachi]

I suspect there is also an insurance rating concern, as the cdl switch turns off the ABS when activated. ABS is a feature that usually provides a discount with insurors.

I suspect DOT had an issue with the fact that the switch allowed the driver to disable ABS in hi-range, thus no switch. As for why we didn't get the cupholder??? Probably because it blocks the view of the radio display.

 

[OZCAL]

I suspect DOT had an issue with the fact that the switch allowed the driver to disable ABS in hi-range, thus no switch.

Yep that makes more sense.

 

[Fochdog]

Why don't the US cruisers have the CDL switch fitted ?.All Australian cruisers have them fitted except the Base models which are part timers and those with the Viscous copling fitted instead

No FMVSS requirement for ABS. Don't forget ABS is still an option on some vehicles, not standard.

I feel the CDL swtich was removed from '93-97 due to the addition of the Vicous Coupling (VC) in the T-case.

Without the VC (with open center diff. only) the vehicle would be very limited in any type loose or slippery surface. So Mr. T gave the driver the option to lock your center diff. to help with low traction conditions.

However, when you spin your tires on a loose or slippery surface the VC will begin to hump and lock momentarily. This eliminates the need for a separate CDL switch.

A VC will begin to hump (really ... thats what they call it) when it see a certain amount of speed delta for a certain amount of time. In the Land Cruiser's t-case when the front and rear props are spinning different speeds.

 

[Bryan E.]

You only get into shift points when you unplug the connector on the transfer case, the 4-Lo signal goes to the ECU/TCM via pin 9 or 19 depending on year. Shift points are not affected by pin presence or removal of 7. The pin 7 mod only kills the 4-Lo signal to the CDL control relay preventing automatic locking of the CDL.

RavenTail, It seems from Dan's instructions in the Pin 7 mod of the Tech Links, he say's the shift points change with the p7 mod, and I do have to agree. My 94 now stay's in first gear in Low Range until going a pretty good speed, then jumps up to second, and downshifts quickly as I let off. He say's before this mod. it will up-shift quickly, which is what I remember mine did. I'm not sure I like the holding in gear so long though. I like to drive mountain jeep roads/trails- slowly in low range, but shifting manually at times. Don't know if it will work the same now. Might work even better.
... Does anyone like another mod better than P7, like the original transfer case wire unpluged??

 

[RavenTai]

RavenTail, It seems from Dan's instructions in the Pin 7 mod of the Tech Links, he say's the shift points change with the p7 mod, and I do have to agree. My 94 now stay's in first gear in Low Range until going a pretty good speed, then jumps up to second, and downshifts quickly as I let off. He say's before this mod. it will up-shift quickly, which is what I remember mine did. I'm not sure I like the holding in gear so long though. I like to drive mountain jeep roads/trails- slowly in low range, but shifting manually at times. Don't know if it will work the same now. Might work even better.
... Does anyone like another mod better than P7, like the original transfer case wire unpluged??

I think you are misreading Dan

Rogue,

Ask and ye shall receive:

Remove the dead pedal and the left front sill plate. In the left kick panel you will find a Silver metal box. That is the ABS ECU. Remove it, and behind you will find a black plastic relay about the size of a cigarette pack. It says "transmission control relay" on it. That's what you are after. The EWD calls it the "center diff lock relay", same thing. Unplug the harness from it and take a terminal pick and remove the black wire with blue tracer from pin#7. Insulate the bare terminal to suit and then put everything else back where you found it. If you have the low 4 position swith at the transfer case unplugged, crawl under there and reconnect that as well.
What you have just accomplished is you have interrupted the signal from the transfer case that tells the lock ECU that you went to low range but you are still sending a signal to the transmission ECU telling it that you ARE in low range. Therefore the transmission will shift in the correct low range pattern. In addition you now have true manual control over center diff locking. It only locks when you tell it to without regard to transfer range selection.
Oh, I forgot the final step......Grab yerself a congratulatory #6 (but not an English one as you have just performed an electrical task, sorry Jim)

Regards.......Dan

Let me try a more detailed explanation and history maybe it will be more clear.

From the factory: when you shift the transfer case into Low, besides changing the gear ration of the T-case 2 other changes are made to the drive train.
The Center Differential Locks
The transmission uses the higher shift points you describe.

The way this is done is a switch on the transfer case watches for Low, when you shift into Low it sends a signal two places,

To the CDL control relay via pin 7 so the CDL relay will command the CDL to lock
Also to the TCM or ECM Via pin 9 or 19 depending on year so that it will use the higher shifting points wile in low.

Long before I bought a cruiser 80 owners were unhappy with the auto locking of the CDL, the first primitive but effective fix was to just disconnect the switch on the T-case. This tricked the CDL control relay into thinking you were always in 4-High so it never locked the CDL, But this also had the side effect of tricking the TCU or ECU into thinking you were always in High so it kept using the 4-Hi lower RPM shift points, another problem was that left the switch and connector exposed to the elements, water, dirt, mud, salt etc.

Then came the more elegant Pin 7 mod, where instead of completely unhooking the 4-low switch on the T-case you only disconnect pin 7 at the CDL control relay. It interrupts the signal to the CDL control relay only so auto locking of the CDL is stopped but the TCM/ECM still gets the 4-low signal so you the correct shift points for T-case range.


If you were to disconnect the connector on the t-case you would loose the proper shift points in low.

If you are on a road that calls for slow driving in low range but don’t want all the shifting there is another fix that can be done from the drives seat on the fly for the 95-97 80’s with the more “refined / pussy” A343F transmission by putting the transmission shifter into 2nd gear and selecting the second start switch, when ypu need it you can go back to drive and unselect the 2nd start switch.

There may be a similar trick for the “Crude / massive“ A442F transmission in the 93-94 80’s I don’t know.

There ahs been some talk about putting a switch on the pin 9/19 signal to allow you to select witch set of shift points you want on the fly wile in low, as far as I can tell it should work just fine but AFAIK no one has ever tried it.

on either transmission if you want it to stay in first just put in in first gear and it will stay there.

 

[Gold Finger]

Quotes From Raven "Long before I bought a cruiser 80 owners were unhappy with the auto locking of the CDL, the first primitive but effective fix was to just disconnect the switch on the T-case. This tricked the CDL control relay into thinking you were always in 4-High so it never locked the CDL, But this also had the side effect of tricking the TCU or ECU into thinking you were always in High so it kept using the 4-Hi lower RPM shift points, another problem was that left the switch and connector exposed to the elements, water, dirt, mud, salt etc."

"There ahs been some talk about putting a switch on the pin 9/19 signal to allow you to select witch set of shift points you want on the fly wile in low, as far as I can tell it should work just fine but AFAIK no one has ever tried it."

I find the pre determined change points when in low a bit of a pain because there are times when running between difficult sections and the engine is revving at an unnecessary rate but switching into high and then back into low would be a pain . I have done the 7pin mod and find it very useful but would like the shift points that come with high ratio but would still like to retain the function of the intended shift points when in low because there are situations when that is preferred, I have thought of putting a wire down to the switch on the back of the transfer box but have not got around to it as yet to allow me to run a switch that would enable me to make the choice of shift points my self, which is the way I like it. It looks interesting that the same thing could be achieved by attending to pins 9 and 10 and if that could be confirmed then that would be another option.

I wonder if I do put a switch to the transfer box lower switch I have a choice of which wire to cut to put in the switch circuit or to just remove both wires from the transfer box switch altogether and join them up with my own switch circuit. The latter could then perhaps also be used in high ratio like a sort of CDL switch perhaps. Has any one any thoughts on any of those suggestions?

 

[RavenTai]

Gold finger you may want to take a look at the earlier threads about this for better details, there are some differences depending on year that I don’t have a full grasp on , may also be differences for your Euro spec diesel powered 80 also,

only one pin/wire needs to be interrupted, on my 96 it is pin 9, on earlier trucks it was pin 19, I don’t know when the change was made but IIRC there was a separate Transmission control module on early 80's and on mine this function is incorporated into the engine control module so that is where the signal now goes instead.

I would think the TCM/ECM change and pin 9/19 change happened with the transmission change but I don’t know for sure,

Another twist is IIRC the 343 change was only on US trucks to lighten the 80 for fuel economy reasons (Dam CAFE) and the Diesel was never sold here, I have no idea what that changes in the controls of the transmission.

Best to refer to an EWD for your model. Once you have that is is pretty straight foreward one wire to cut and splice in a switch.

someone stated the low range (high PRM) shift points are the same as either the ECT (early 80's) or PWR (later 80) settings used in high range, if so then no use trying to get low range shift points wile in high as you already have that option don’t bother, instead look for high range shift points (low RPM) wile in low by interrupting the pin 9 or 19 signal, I would think it would be best to add this switch in the cleaner drier environment of the cab than out on the transfer case. you are just openign a circuit The end result is the same as if it was done outside.

 

[Bryan E.]

RavenTai, You could be correct that I was misreading Dan. I haven't been in L/Range for some time now, so I don't have a definete feel for any change of shift points. It was just from memory of my last time. Now that I've done P7, and CDL sw., it just seemed to hold in first gear in L/Range longer than necesary. I know I can hold it in first by shifting manually in H/R or L/R, but if it's hold in first longer than I want in L/Range, will sifting manually up to second make it shift to second? I'll go try this. If I can be in L/R and totally manual shift at RPM I want, (lower RPM then go to 2nd, or even 3rd) then that would be great. I doubt that will work though.
........I like the idea of another switch wired in that gives a regular high range shift pattern while your in low range, then be able to switch back to the other pattern with flip or push of a switch. This could be a very useful trail option depending on your terrain.

 

[RavenTai]

I know I can hold it in first by shifting manually in H/R or L/R, but if it's hold in first longer than I want in L/Range, will sifting manually up to second make it shift to second? .

I don’t think so on a 94, with second gear selected it will shift between the 1st and second depending on conditions,

on the later trucks there is a 2nd start switch witch locks out first, so on a later truck you can lock it into first or second, on the earlier AFAIK just first.