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Discussion Starter · #1 ·
Just purchased a 79cj7, not sure if it is the standard cj7, or the renegade or laredo. Thinking it may be Laredo, seats look like they may have been top of the line when they were new, now, not so much. Without the decals I can't tell for sure. Does anyone have a link I can check the VIN no. on. It does have the 304 with the TH400 automatic w/QT, if that helps. I would also like to get some opinions on the quadratrac. Thinking of swapping with Dana 18 and new tranny, but not till I get to try out the QT. This is my first CJ, haven't even had it long enough to get it dirty, but I soon plan on fixing that.

Any help will be appreciated, Thanks!
 

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Welcome!

The special models like Laredo and Renegade were trim and option packages. I'm pretty sure there is nothing in the VIN that would tell you that. It would take a registry where you could look up the original invoice or build order for your serial number to find that. As far as I know that went away long ago, but I could be wrong.

Will is our resident Quadratrac expert. He has one that he beats the tar out of regularly with good results. The QT has two peculiarities - the chain and the fluid. The chain is more or less a wear item that needs to be replaced periodically. If run too long it will stretch and eventually start to slip under power. They're neither expensive nor difficult to replace. The fluid is specific to the QTs and substituting can cause problems.

Will can tell you more when he checks in.
 

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You will find a plug dead in the bottom of the Borg Warner 1305 or 1339 Transfer Case,
Always a good idea to remove that plug, use a screwdriver to feel for the chain slop.
Excessive slop, and it's time for a new chain.

That also give you the opportunity to refill the lubricant, which probably hasn't been touched in years...

Switching to a Dana 18 isn't as easy as it sounds, the rear axle is a passenger side off set to match the Borg Warner transfer case output to the rear.
That can cause some drive shaft fitment problems.

Since you have a Narrow track width Jeep,
And since Jeep used a Dana 44 in the narrow track flavor until '74 or '75, it might be a good idea to start by watching for a stronger rear differential if you intend to wheel it much.

The D-44, IF found for reasonable money, it would be a good upgrade if you switch to a manual transmission and Dana 18 or Dana 300

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The Q-Track can be a very tough customer. They get a bad reputation because people don't service them.
With a good chain (NOT something from 'China') they get around just fine.

Your TH 400 is the 800 pound gorilla of automatic transmissions,
But there are a couple of things you need to look for to keep it alive.

One is the 'Kick Down' switch on the throttle linkage.
There should be an electrical switch on your throttle linkage under the dash,
And that connects to an electrical terminal on the drivers side of the transmission case.
That switch MUST be working!

Without it, you WILL burn up the clutch packs in short order.
This particular transmission doesn't use the traditional throttle valve (Cable or linkage to trans) so you must make sure that switch is working.

The other thing is the 'Vacuum Modulator' on the passenger side of the transmission, front.
Without that vacuum modulator hooked up and working, the transmission will 'Shift Stupid' either way late or way early...

These vacuum modulators occasionally need replacement, the diaphragm inside gives up, and you start sucking transmission fluid through them.

There are two kinds,
There is a LARGE stupid looking kind, which usually has a 45 degree elbow attached to the case, then the modulator sticking up at about a 45 degree angle... (front drive shaft clearance)

Or they have a neat little vacuum modulator sticking right out of the case.

The two are NOT interchangeable.
The different canisters will interchange,
But the spool valve inside the transmission is different (Longer) when the Elbow adapter and large canister is used,

And the spool valve is shorter for the smaller, direct bolt on canister.

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Either way, there is an adjustment screw in the vacuum nipple on the canister.
If it's shifting way too early, remove the vacuum line, turn the screw in a couple of turns at a time until you get it shifting where you want it,
If it's shifting too late, then back the screw out,
Don't forget to put the vacuum line back on the nipple!

One other word of warning...
Most of these I see, some PO (Previous Owner) has removed the steel vacuum line down to the canister.

There is supposed to be a steel line, with rubber vacuum line at both ends to connect between manifold and line, then line to vacuum modulator.

If they have run a vacuum line all the way down, the vacuum line contracts under vacuum and expands under less vacuum,
And that TOTALLY SCREWS WITH THE SHIFT POINTS,
You CAN NOT buffer that vacuum signal like that and expect the transmission to shift correctly,
And that line replacement happens WAY TOO OFTEN...

Steel lines are easy to fabricate, just buy a stick of brake line and bend it to fit, cheap and easy!

This should get you up to speed with your PO as far as the things they commonly do wrong you need to look at right away...
 

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also the manual transfer case for that was the Dana 20. you could look for a Dana 300 or whatever if you are thinking of a new transmission.
 

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AMC 20 started in '76 for sure, and lasted through to '85
I don't know about '75, haven't owned one, but I know it was still D-44 in the rear through to '74

The DJ mail Jeeps used D-44 Rears well after everything else went to AMC 20, I've seen D-44's in the rear of DJs until the late 70s.
I have to assume they were stock since who would swap a D-44 into a mail jeep?
 

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Discussion Starter · #8 ·
Thanks for all the info. I am considering keeping the QT after some research last night on my own. Seems like a decent set up. Going to check the chain and change all the fluids this weekend. Thanks again!
 

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Switching to a Dana 18 isn't as easy as it sounds, the rear axle is a passenger side off set to match the Borg Warner transfer case output to the rear.
That can cause some drive shaft fitment problems.

Since you have a Narrow track width Jeep,
And since Jeep used a Dana 44 in the narrow track flavor until '74 or '75, it might be a good idea to start by watching for a stronger rear differential if you intend to wheel it much.

The D-44, IF found for reasonable money, it would be a good upgrade if you switch to a manual transmission and Dana 18 or Dana 300

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Just a little correction here. The dana 18 is an offset rear output transfer case too. To swap it in, you'll need a TH400 to dana 18 adapter kit which will also require taking the transmission completely apart to change the output shaft. There was a factory adapter used with the dana 20 which uses the same case as the last dana 18 but it is said to be weaker than the aftermarket adapters.

I do like the QT transfer case. I've had my 79 CJ7 since 1994. I have changed the chain out a few times. When it starts jumping under heavy load, it is time to change it. TCL-1 is the correct fluid to use with it.

I moved the vacuum switch from the glove box to next to the headlight switch to make it easier to reach.

I have swapped most of the drivetrain in my jeep but have kept the QT. I have a 700r4 in front of it now. I also used dana 44 axles from a 1975 Cherokee that had a quadratrac. I have lockrights in both axles. In full time mode, the torque steer is terrible so I put locking hubs on the front and leave the transfer case locked (emergency drive) while on the road.
 

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I STAND CORRECTED.
I saw dana 18, was thinking Dana 20 since that's what I deal with most.
Sorry, brain fart.

I can't keep Dana 18's straight, large pinion, small pinion, this and that...
I throw a 20 or 300 at them and get it over with! :p
 

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Discussion Starter · #11 ·
Thanks for the clarification Will. I thought the 18 was offset as well. I am going to stick with the QT for now. I've only had my cj for a week now, so I've got to give it a chance and feel things out. Nice tip on moving the switch, seems a little rediculous to have it on the passenger side in the glove box. Did the 79 come with a low range option, or is that an aftermarket add-on? I have a low range selector switch on the floor next to the driver seat, don't know if it works yet, hope to find out everything this weekend. Read that the QT didn't come with low range on earlier models, but couldn't find anything on 79 specific.
 

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The BW 1305 didn't come with a low range box on the transfer case,
The BW 1339 is the version WITH the low range case, and it can be added to the 1305 pretty easy.

I've never seen a CJ without a low range box (1339) version from the factory.
People say they are out there, but I've never seen one.

Low range is just that, low range,
You still have to have a working 'Emergency Drive' to have both axles driven together...
When the emergency drive isn't working (and they often don't, rotted vacuum lines, stuck vacuum solenoid, ect.) you only drive one axle at a time, and it will alternate between front and rear.

With open axles, you get one front tire pulling or one rear tire pulling,
When the emergency drive is activated,
You get one tire on both ends pulling.
(Which makes for some REAL FUN on ice!)

When you don't have 'Emergency Drive' locked in, the transfer case works like an open differential between axles,
If one is spinning and the other has traction, you get the power to the spinning axle instead of the traction axle... Which sucks...

There is a 'Part Time' kit you can install, where you can use lockouts on the front and unlock axles from wheels,
And turn off the front drive shaft entirely, which saves fuel, wear and tear on the front axle/drive shaft...
And it stops that stupid 'Push/Pull' thing between axles.
It's not hard to install, I've done 3 or 4 of them...

Some people say the part time kits are harder on the chain, but I don't see how that could be true, driving one axle at a time STEADILY can't be any harder than driving one axle at a time when it alternates on 'Slick' roads...
But I'm not the Q-Track expert some folks are...
Maybe someone can elaborate on it?

I TOTALLY HATED the Q-track in the beginning.
I'd seen the blown out cases from broken chains, and was dead set against them.
I ran one in a J-20 truck several thousand miles with no issues, and it never let me down, and it had several thousand on it when I got it.
When it started 'Skipping'... new chain, sprockets and it was fine with no issues, and I beat the CRAP out of it thinking the sooner it died, the sooner I'd get a 'Real' transfer case.

TOTALLY CHANGED MY MIND!
That truck was my 'Scrap Hauler', and I put dual wheels in the back, loaded 12,000 pounds in the bed of a 3/4 ton pickup, wedged hardwood 2x4's in the springs to keep the bumper from dragging the ground, and drove it like it was stolen...
NO BREAKAGE! Couldn't kill it...
It finally got totaled when a 17 year old kid missed a curve and hit it in the driveway...
 

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When you don't have 'Emergency Drive' locked in, the transfer case works like an open differential between axles
Actually, it is a limited slip unless it is worn out. They rarely wear out though. Usually the opposite... they stick too well and require making figure 8's in a parking lot to break them loose.

Some people say the part time kits are harder on the chain, but I don't see how that could be true
I agree

When it started 'Skipping'... new chain, sprockets and it was fine with no issues
I've never heard of anyone changing the sprockets.

I put dual wheels in the back, loaded 12,000 pounds in the bed of a 3/4 ton pickup, wedged hardwood 2x4's in the springs to keep the bumper from dragging the ground, and drove it like it was stolen...
NO BREAKAGE! Couldn't kill it.
To be fair, it is a full float dana 60 rear axle and a heavy duty dana 44 front axle.
 

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I heard about figure 8's in reverse even, after I quit running on.

I've never heard of anyone changing the sprockets.
If you would have seen the sprockets, you would have changed them.
I had a 1305 laying here, so I stole parts.
Still have a 1339 laying here, just in case I want to run one again sometime.

To be fair, it is a full float dana 60 rear axle and a heavy duty dana 44 front axle.
It was a 1 ton dual wheel out of a dodge with a flat bed where the bed rusted off the truck.
Like I said, it was a junk hauler... Didn't much care what it looked like, but it would tow around 3 pallets of batteries stacked 4 high, and that I did care about...

Still a butt load of stress on that chain when I was swamping in and out of the river bottoms with seed or fertilizer on the back,
Or towing a load of batteries to the recycler.

Once it had a chain worth spit that didn't have 4 or 5 inces of deflection it in, the T-case worked like a champ. Couldn't complain and believe me, I was ready to complain!
 

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1/2" of deflection isn't even rubbing on the case yet...
Seen a bunch of time rubbing on the case and still working fine...
Brand new chains have 1/2" of deflection out of the box...

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Anyway, Something that OP can use...

Vacuum switch, hose routing, vacuum solenoid at transfer case, ect.
See below what that vacuum solenoid moves around to lock the front/rear together.



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Here is the 'Sleeve' that locks front and rear together, and the lugs that get locked together,



And here is the locking ring in place over those drive lugs.
This is the part that vacuum solenoid move around when you hit 'Emergency Drive' switch...



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This is the 'Forcing Cone', (In the hand) much smaller version of the same design GM used in it's early 'Posi' rear differentials, and they quit using them because of the same reason, the forcing cones wore out and the posi didn't work anymore,
Or the forcing cones became wedged in the housings and wouldn't unlock.



Remember, those forcing cones wear out VERY QUICKLY, and don't last at all if you use the wrong lubrication, ATF is NOT the correct lubricant...
And if a PO used ATF, that forcing cone ('Screw Clutch') is done, I can guarantee it...

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And this is the LITTLE BITTY spider gear set inside that releases front/rear torsional stresses when front axle and rear axle run at different speeds, like around corners or when you spin the rear tires and not the front tires or vice versa...



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SO,
When I say you probably have an 'Open Differental' in the transfer case,
that simply means the forcing cones
('Screw Clutch' if you don't know exactly what it is and how it works...)
are worn to the point they are useless...
So no matter how many 'Experts' tell you there is a 'Limited Slip' or 'Posi' until in the BW 1305 case,
You probably DO NOT have one, most are shot from normal wear, and or POs that put the wrong lubricant in the case...

Unless you can take a drive shaft out,
And still move, you don't have a 'Pois' or 'Limited Slip'... Which is the actual test if you still have 'Limited Slip' or not.

The 'Emergency Drive' will work when the forcing cones are shot.
When in 'Emergency Drive' the front/rear are locked together, so driving in 'Emergency Drive' on hard pack roads with lots of traction is a BAD IDEA...
And makes it REALLY unpredictable/hard to steer at times,

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If you take a look at the 'Emergency Drive' vacuum switch,
Vacuum is applied to one side or the other of the vacuum solenoid.
When ANY line rots out, gets disconnected, the locking collar can move around.

The switch either holds the locking collar FULLY DISENGAGED,
Or FULLY ENGAGED,

So when the lines rot out, the collar/shift fork can move around, and you can grind the crap out of the drive dogs or collar it's self...
So having GOOD LINES on at all times is a pretty good idea...

I've had to scrounge hard parts more than once for someone that though the vacuum lines didn't need to be connected if they weren't going to use the 'Emergency Drive'...

And if you don't wan to mess with the 'Emergency Drive' switch and vacuum likes, there are manual linkages and cable adapters out there, or you can make your own.

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Now, one other thing to consider,
The 'Factory' quality parts have dried up, this is an OBSOLETE transfer case.
The 'China' replacement stuff wears out about once a year,
And if you can find 'Factory' replacement parts, the guys want an arm and a leg for them... *IF* they will turn loose of them at all...
 

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Unless you can take a drive shaft out,
And still move, you don't have a 'Pois' or 'Limited Slip'... Which is the actual test if you still have 'Limited Slip' or not.
I took out my front driveshaft once and went for a drive. I was almost back when I heard a strange noise. I was going up a fairly steep road and found out my vacuum shifter hadn't locked it into "emergency drive." It was that tight.

So when the lines rot out, the collar/shift fork can move around, and you can grind the crap out of the drive dogs or collar it's self
That collar won't move around. There is no side loading on it and the shift fork shaft has detents in it. I was on one trip that the vacuum shifter quit working. I had to borrow a wrench from one of the other guys in the group and remove the cover over the shift fork to slide the fork by hand. (I found out the value of gear wrenches that day.) It stayed locked for the rest of the trip.
 

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I took out my front driveshaft once and went for a drive. I was almost back when I heard a strange noise. I was going up a fairly steep road and found out my vacuum shifter hadn't locked it into "emergency drive." It was that tight.

That collar won't move around. There is no side loading on it and the shift fork shaft has detents in it. I was on one trip that the vacuum shifter quit working. I had to borrow a wrench from one of the other guys in the group and remove the cover over the shift fork to slide the fork by hand. (I found out the value of gear wrenches that day.) It stayed locked for the rest of the trip.
That seems contradictory to me...
If you were driving around and heard a strange noise going up a hill,
But you say the shift fork/collar can't move around,
What caused the nose?
Sounds like the collar/fork moved and was grinding a few lugs...
(Just like I said it would)

I'm glad you have a detent that works, it would suck to have to keep trying to reach up in there and manually engage,
Did you fix the detent after the incident described in the first anecdote?

And I'm glad you have good clutches,

But not everyone does. And that was the point I was TRYING to make...

Like I said, the test is to take that drive shaft out and see if the vehicle moves or you just spin the yoke that has nothing attached to it (open diff/no forcing cone friction surface left).

Why on earth would you take the front drive shaft out just to go for ride?
That doesn't exactly make sense either...
But the moving around locking collar sure makes my point pretty well, so I'm glad you shared it.

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To get rid of the vacuum altogether, you could use a cable pretty easily.
The home made version uses the vacuum solenoid its self, you simply connect a cable to the existing rod and mount the cable stop on the blunt side of the vacuum canister.

There's also a goofy mechanical linkage, I don't think much of that.
Too many moving parts you have to fabricate and keep track off.
Lots of places for mud to get into and turn solid when you needed to lock in.

It's a LOT EASIER to lube that cable once in a while instead of trying to take that top cover off to reach the fork linkage!
 
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