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My AW4 swap into a '72 Javelin

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CamJam View Drop Down
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    Posted: Sep/21/2018 at 8:40pm
NOTE:  This write-up is still a work in process.  Will be updated with more photos and descriptions as I go.

I recently installed an AW4 O/D automatic transmission into my '72/304 Javelin and want to document it for others who might want to try this swap in future.  



The AW4 is a 4-speed with a .75 overdrive final ratio.  It was jointly developed by AMC and Borg-Warner and was manufactured by Aisin-Warner.  It was used in 87-2001 Jeep Cherokee (XJ), and versions of it-- known as the A340-- were also used by Toyota, Lexus, Volvo and Isuzu. More info here.  The beauty of this swap is that the Jeep 4.0 has the same bolt pattern as the 72-up AMC V8s.  Pre-72 V8s would need a crank adapter. 

Gear ratios for the AW4 are 2.80, 1.53, 1.00 & .75. Acceleration feels stronger than it did with the 998, probably because of the shorter 1st and 2nd gear. The ratios seem about perfect with my 3.15 rear diff.

Rick Jones (SC397) has already done this swap into a '69 Javelin, and there is a sticky here I'd suggest you read first. It's largely what I followed, but there are some differences in the later Javelins since AMC switched to Torqueflites in '72.  These actually make the swap easier. Because the length of the AW4 is within 1/2" of the TF998, the original driveshaft can be used without modification.  You just need to use the front slip yoke from the Jeep. The Jeep XJ used the same U-joints as the Javelin, so it's just a matter of putting the Jeep yoke onto the Javelin driveshaft.  I recommend rebalancing the driveshaft since mine was out of balance after replacing the yoke.

In the '72, the original console floor shifter can be used too.  The original linkage comes very close to where it's needed in the AW4. I was able to clamp an end I cut off the Jeep's shift cable to the Javelin linkage (see photo below).  I probably should have it welded, but it's working so well I wonder if that's necessary. The only problem is that the indexing is off slightly, but I suspect that could be corrected by fabricating a slightly longer transmission shifter bracket so that it moves in a larger arc. It would take a little bit of effort to figure out the right length and hasn't been a priority for me, but will make a good spare time project.

Another 72+ AMC change that works on our favor is the starter relay, which interfaces nicely with the Jeep neutral safety switch (NSS). On his '69, Rick had to devise some circuitry for the NSS to work properly, but starting in '72 the AMC starter relays have an extra ground post on the back.  This post has to be grounded by the NSS before the relay will send 12V to the starter.  Since we use the starter and flex plate from the Jeep, and the Jeep has the solenoid attached to the top of the starter, I simply bypassed the Jeep's solenoid with a jumper and used the original AMC relay.

The speedometer is easy too. If using a 91+ AW4, you'll need to grab a mechanical speedometer drive from a pre-91 XJ, which will bolt right into the later transmission.  You can then use the original Javelin speedo cable, though you might have to change the mechanical drive's plastic gear in order to make the speedo read accurately. That's a five-minute job.

The donor vehicle should be a pre-96 2WD Jeep Cherokee. I'm told it takes a lot of work to convert a 4WD AW4 to a 2WD, so may as well start with a 2WD.  Using a 97-01 transmission is possible, but requires more work. Starting in mid-96 Jeep switched to OBDII and tied the Transmission Control Unit (TCU) into the the vehicle PCM. Prior to that, the TCU was a standalone unit. In fact, you can even run without a TCU if you don't mind switching gears manually.  It does not matter if your TCU is from a 2WD or 4WD, and I'm told you can use TCU from different years, but to avoid problems I would try to find a TCU that is close to the same year as your transmission. Some wiring and TPS changes were made through the years, though it appears the transmissions themselves went largely unchanged. 

There are somewhere around a dozen wired connections that need to be made between the transmission and the TCU, and a few that need to go to the throttle position sensor (TPS), brake switch plus 12 volts to the fuse panel and grounds.  It seems a bit daunting at first, but is actually quite easy. Just take your time so that you don't make any errors. Do yourself a favor and buy some high-quality crimpers and crimp connectors... not the junk they sell at the chain stores.  I put the TCU in the Javelin glove box (see photo) which makes it easy to route the cables out the back and through the firewall. 

I used the original Javelin transmission crossmember with an Anchor #2253 mount. That mount fits a lot of 60s & 70s Fords.  It has two studs that need to be knocked out-- a sledge hammer makes short work of them-- and then you'll need some metric allen-head bolts (needed because of their smaller head) to replace them.  The hole spacing is correct for the AW4, but you'll have to drill a couple extra access holes to tighten the bolts down. Rick's sticky details a small piece that needs to be cut off the tail shaft of the transmission.  I can vouch for the fact that you will need to remove this if you want to use the original crossmember. I had to move the crossmember back to the rear-most set of frame rail holes-- which is one or two holes back from the original location as I recall.

Transmission oil cooler lines were a bit problematic, only because the adapters were hard to find. The transmission has M14x1.5 ORB fittings and the Javelin lines are 5/16 flare as I recall. I had to resort to barb hose fittings and a short length of rubber transmission line to get it all to work, but I'll be adding a transmission oil cooler soon so will be redoing that anyway. AW4s have a reputation for being tough transmissions, but they apparently do run hot, so an external cooler seems like good insurance. The factory AMC lines come close to where they need to be for the AW4, but some rebending is required if you plan to use the factory steel lines. 

The Jeep's kick-down cable was used, and with a little redneck engineering I managed to attach it to the Javelin's original kick-down linkage.  The TPS bracket I bought off Amazon (see photo below) came with an extra piece that I used for attaching the kick-down cable to the throttle cable bracket

The "stop light switch" (see pin-outs chart below) controls the lock-up of the torque converter by grounding TCU wire C10. The Jeep uses a normally-closed switch to control the TC, meaning 1) the wire is always grounded and TC is always in lock-up enable mode unless the brake pedal is depressed, and 2) if you don't connect this wire to anything the TC will never lock up.  I'm not sure if this is harmful or not, but Internet legend says the transmission runs hotter when the TC isn't locked-up. Anyway, I like the fuel economy benefits of a lock-up TC, so why not hook it up? I've ordered a spring operated switch that is normally open, since these are commonly used for ATV rear brake lights and readily available.  I will be mounting it to the steering column, below the brake pedal, and will use spring tension to keep it closed except when the brake pedal is pressed.  If this works out I'll update this post with details of where to get the switch.  In the meantime, I have verified that that TC lock-up is working as it should by temporarily wiring in a momentary switch.

What you'll need from the Jeep:

AW4 transmission with torque converter from pre-96 2WD Jeep XJ
Flex plate. You will need to have it match-balanced to your original flex plate. 
Starter
TCU (In the XJ you'll find this behind a panel on passenger's side dash)
Transmission harnesses (normally already attached to transmission)
Mating connectors for transmission harnesses and TCU cut from the Jeep's wiring harness
Shift and kick-down cables
Mechanical speedometer drive from a pre-91 XJ
Front (slip) yoke from Jeep driveshaft.

I mounted the TCU in the glovebox. It's easy to access and convenient for running wires through the firewall.



I pre-made a harness on my kitchen table, then just crimped the ends to the TCU harness once I'd run my wires through the firewall.  I covered all the connections with shrink tubing and put flexible plastic conduit over the cables when I was finished.  The box in the center of the photo is the TCU:





I cut this end off the Jeep's shift cable and clamped it to the Javelin's linkage with a "U" type cable clamp.  That's all it took to attach the Javelin's shift linkage to the transmission. I had planned to weld the end onto the original linkage, but it's working so well that I might just leave it.  You'll see it in the 2nd photo as well, blue arrow. Basically I clamped the metal tail of this piece (green arrow) to the Javelin's shift rod (orange arrow).  No modifications at all were made to the Javelin shift linkage, and you can see how close it came to where it needed to be.





A throttle position sensor is necessary to tell the TCU when to shift. I used the TPS from a '94 Cherokee, same year as my transmission, and mounted it to this throttle cable bracket I found on Amazon. I had to cut some pieces of the bracket that weren't needed.  I later added a pulley and cable arrangement to the TPS and connected it to the throttle. I understand that the TPS on pre-91 XJs have a lever that might be easier to interface to the throttle cable, but I don't know whether or not they are electrically the same.  You'll need a 12-to-5 volt DC converter to run the TPS.  I also found this on Amazon for less than $10, and mounted it under the dash.



Here's the pulley attached to the TPS:



I made the pulley out of a couple of shock absorber washers, then cut grooves in the bolt to match the slots in the TPS and epoxied the bolt into the TPS.  Obviously, be VERY careful with the epoxy or you can easily prevent your TPS from rotating. This pulley arrangement works, but I'd rather find a compatible TPS that is actuated by a lever. I believe pre '91 (Renix era) XJ have such a TPS, but it's 12V instead of 5V and therefore I'm not sure if it's compatible with my '94 TCU.  



This is the electronic speedometer drive that was in my 1994 AW4.  I simply removed it and replaced it with a mechanical one from an '89 XJ at the Pick n' Pull. The Javelin's original speedometer cable connected directly to it, though I'll need to change the gear to make the speedo read accurately:



Here are the pin-outs for the 1994 AW4 that I used.  I believe that this information is correct for 91 thru mid-96 TCUs.  These TCUs are easy to spot by their green connector (see above photo) while post-96 will have a black TCU connector and different pin-outs. The only other connector is for the TPS, which in these years was a 3-wire connector, +5 VDC, -5 VDC and data (to D2 of the TCU connector).






Edited by CamJam - Nov/28/2018 at 9:28pm
'69 Big Bad Orange AMX 390
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Sep/24/2018 at 11:22pm
So, how does it drive?

The answer is that 1/4 mile times are almost exactly the same as before, according to my admittedly unscientific testing method (a phone app), but the car feels stronger and actually burns rubber on take off now, which it didn't do before unless there was gravel on the road.  It seems to hold the gears longer than before-- maybe a little too long at full throttle-- though I don't have a tach on the car to verify that. Seems like the engine runs out of steam and that it might be a little quicker if the car shifted sooner. I guess I could shift it manually to verify that but I haven't tried it. 

Here's a little YouTube video I made of a short run up and down the hill outside my subdivision.  I tried to turn the volume up so you could hear the shifts.  I put a little GPS heads-up speed display on the windshield above the speaker grill though it's pretty hard to see in the bright lite and flickers in the video even though it doesn't when viewed live


The real benefit, as you might expect from the O/D gear, is on the highway. 70-75 mph seems like a comfortable cruising speed now compared to 65 mph before.  I calculate that the rpm dropped by about 800 at 70 mph.  Like I said, there is no tach in the car, but when I typed my tire diameter and gear ratios into a calculator that's the number I got.


Edited by CamJam - Sep/24/2018 at 11:26pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Sep/25/2018 at 5:46am
Camjam, as a side note... since you brought up a list of manufacturers that used the A340E, the 98 to 2001 Toyota twin turbo Supra has probably the most durable one ever made. It has some special parts that are unique to the build and cannot be swapped. So I imagine the case is revamped internally for the parts used. One negative, is it may use a slightly larger torque converter, over the jeep version. Thus the jeep bell housing may not be large enough. Out side of possible component size limitations, the rarity of finding wrecked twin turbo Supras or their salvaged parts at a good price is probably an expensive option, for making a bolt on swap.

The plus side... peeps with the twin turbo Supra have been known to upgrade the turbos and tune to get up to 1000hp on stock parts.

So, if anyone who has the resources and is willing to investigate further, may want to add or give it a try, if finding there is no limitations with the swap.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/25/2018 at 6:13am
You just do have enough gear for the OD. 87-90 models have a 0.705:1 OD, 91+ has 0.75:1 OD. There is about 120 rpm difference. With 3.15 gears, 26" diameter tire (215/65R15), 65 mph, .705 = 1865.4 rpm; same with .75 = 1984.5 rpm.  Typically you want to cruise at about 2000 rpm in order to be in the torque band with a stock or mild cam. You want to be about 200-300 rpm over where the cam "comes in" so you're in the torque band enough to pull the car without working the engine overly hard. Gives you 100-200 rpm to drop when the car starts pulling a hill before you have to push on the gas pedal a good bit more. With a 26" tire you're just there with the 3.16 gears at 70 mph (2137.2 rpm). If you have a bigger tire, say a 225/70R15 (27.4" diameter) you're still JUST there at 2028 rpm@70... but just under at 1883 rpm@65. If your cam is advertised at 1800-3500 rpm or something like that, I'd say the calculated 1885@65 is probably slow enough that the engine will work a bit harder, especially given some error in tire diameter and other drivetrain losses.

It won't strain, but will work enough harder that gas mileage will go down. I tried a 3.08 gear initially with my .70 AW4. Had to cruise at 75+ to be in a good rpm range in OD. I dropped to a 3.55 gear (what the XJ uses with an AW4) and actually gained an average of 2 mpg due to easier starts and being in the torque band. I would suspect a 3.31 gear would be near ideal for me (just a cruiser), but not enough difference for the expense of changing gears (I have a Jag IRS...  3.55 is pretty common, 3.31 was used only in some European models). Just a tad more gear like a 3.31 would be better for you, but I suspect a 3.55 would be more to your liking if you plan on any bracket racing. With a 27.4" tire (225/70R15) it would turn 2122.2 rpm @ 65, 2285.5 @ 70... only a 267 rpm rise @70.

I use the calculators at www.4lo.com for tire diameter and gear ratio. Just ignore the LT in front of tire size (Light Truck is the same sizing as a car tire, just a bit more aggressive tread design), and put in a "1" for transfer case ratio. Other calculators are pretty much the same, that's just an easy site to remember.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Sep/25/2018 at 4:10pm

Thanks for the info, Frank.  I have an eight mile drive to town, most of which is at a 65 mph speed limit, with a slight uphill climb most of the way home.  I do notice that the TC drops out of lock-up mode when I hit the slope, but it stays in 4th and doesn't shift into 3rd.  Probably a 3.31 ratio would be perfect, as you say.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Sep/25/2018 at 5:33pm
As for proper rpm and overdrive. I am not sure, but with our Toyota overdrive can be shut off and still use the lockup converter. Though it is not the same tranny, but is a 2000 car, and some jeeps had an overdrive switch, like our Toyota.

Donno but for us in the Midwest 80 to 90 MPH is norm driving in the interstate. As soon as your comfy with cruise set, somebody will find you and pass you for going 80.

I saw your video, so your driving seems more twisty than straight ahead. So you may not see much improvement in MPG anyway.

One big note... many who have been reporting MPG with our newer car model, have been running below the power band, around 65MPH, but for us, I note that 70MPH is at our power band start which is a wee over 2500 RPM. I got pretty good milage going over the speed limit at 75 average, considering.

Edited by 304-dude - Sep/25/2018 at 5:38pm
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (1) Thanks(1)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2018 at 9:59pm
I've got about 1,000 miles on my AW4 now, and have a couple more things to share.

I had a crimp on the chassis ground of the TPS (pin D3 of the TCU connector) come loose at one point.  From the symptoms, I was pretty sure what the problem might be and found it quickly, but thought I'd share these symptoms in case anyone else runs into this problem.

* Shift points were a lot higher than usual, especially with light throttle in 1st gear.
* No kick-down when passing or climbing hills.

Basically with no TPS it seems all shift points become speed dependent, regardless of throttle position.
 
It should be noted that shift points are always a little higher than usual until the transmission reaches normal operating temperature. 

The torque converter locks up almost as soon as the transmission shifts into 4th gear. It will even happily lope along at 1,500 rpm with the TC locked up. This isn't a problem, but it's obviously programmed to maximize fuel economy.  Of course, you can always move the shift lever from "D" to "3" if you don't like this behavior while driving around town and move it back later for highway driving. Personally, I just leave it in D at all times.   

As soon as you step on the brake even a little the TC lock-up switches off and the rpm will rise slightly.  This makes for a quick way to check that the TC lock-up is operating properly, just give it light throttle and light brake simultaneously and you should hear (or see with a tach) the rpm rise.

With my 304 and the AW4 I averaged 17.2 mpg on my 700 mile trip to Las Vegas and back last month, much of the drive at 70-75 mph.

It's nice to know that even if all your electronics and sensors fail, the AW4 is still driveable. If the TCU fails, you can still shift manually with the shift lever.  If the TPS fails the shift points will be off, but you won't be dead in the water.  The TC lock-up defaults to "off", so if your brake switch fails it just means your TC won't lock up and your 4th gear revs will be slightly higher.  Your fuel mileage will suffer accordingly, but you'll get home.



Edited by CamJam - Nov/28/2018 at 11:00pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote javhunter74 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2018 at 3:15pm
Thanks for this post. Great information.  I have been eyeing up 4L60's for some time.  I never realized how much easier this would be using the AW4.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DragRacingSpirit Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2018 at 4:36pm
If the AW4 could hold up to a 500HP hot street 401 and have a selection of torque converters it would be interesting.

Until then I just dream of a gear vendors unit for my switch pitch 400 turbo.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2018 at 5:07pm
Originally posted by DragRacingSpirit DragRacingSpirit wrote:

If the AW4 could hold up to a 500HP hot street 401 and have a selection of torque converters it would be interesting.

Until then I just dream of a gear vendors unit for my switch pitch 400 turbo.

Here I thought I was the only one going that route... few have switch pitch 400 trannies and even fewer have the gear vendor setup. 
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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