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89 Comanche TCU upgrade


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I know this topic has been based out before trying to find good info for people that s actually completed this mod.

 

I have a Bone Stock 89 Comanche pioneer that I want to keep mostly stock Renix but put a few "upgrades" on. Read article on swapping a 90 model TCU, I have a 91 TCU but plug is different. Any info would be appreciated.

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I know this topic has been based out before trying to find good info for people that s actually completed this mod.

 

I have a Bone Stock 89 Comanche pioneer that I want to keep mostly stock Renix but put a few "upgrades" on. Read article on swapping a 90 model TCU, I have a 91 TCU but plug is different. Any info would be appreciated.

 

TCU? TCU = Transmission Control Unit. Not an upgrade. You must mean ECU. Pretty sure the Renix 89 and 90 ECUs are the same.

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Well I read a couple of cool write ups on the AW-4 were they wired it to switches for manual shifting. I'm not sure about the usefulness of that but it was supposed to be a "preformance"up grade, I also read one that put a switch on the ground of the TCU to keep it in 1st gear while trail riding. But supposedly one swapped an 90 model TCU into a 88 Comanche and it improved the "OUTPUT" of the Comanche. I do know that in later Cherokees the TCU was integrated into the ECUs but I don't know when and I'm not sure about the H.O. Comanches.

 

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changing the ECU won`t give you much of an upgrade other than altering the shift points, if anything... adding more beef to the trans cooler and/or adding better clutches are worthy upgrades, if you can afford them...

 

also adding the manual shifter has more advantages than you think:

 

- with the proper wiring you can keep the TCU if you want to go auto at anytime

- you can start in 2nd on snow or mud (you can`t manually start in 2nd on a stock aw4)

- for uphill/downhill you can select the right gear faster than the TCU can predict and stay on that gear, no more gear hunting

- on the highway you can go throught the gears and lock the TC sooner for better MPGs

 

 

and many more

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May have to revisit the wiring as I don't yet understand the reasoning behind it. I know you can get shift kits for the AW-4 but I not quite sure about going into the transmission I've read with mixed reviews that the AW-4 doesn't like rebuilds

 

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I read that swapping the tcu from an H.O. changed the shift points and "upgraded" a Renix.

 

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False info. 88 to 90 TCUs are pretty much the same 7 was the oddball.

 

The 91 TCU plugs in,but the wiring is different. Don't do it. 

 

Ever done this?

 

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May have to revisit the wiring as I don't yet understand the reasoning behind it. I know you can get shift kits for the AW-4 but I not quite sure about going into the transmission I've read with mixed reviews that the AW-4 doesn't like rebuilds

 

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You are referring to the power/comfort switch. When set in "comfort" mode the shift points were at a lower RPM and not as crisp. In "power" mode the shift points were raised to a higher RPM and shifts were a bit firmer. Most of us just set the switch in "power" mode and forget it. The HO change you are referring to was simply the elimination of the switch, and hard-wiring it to the "power" setting. If you have the switch (and it works), you don't need to "upgrade" anything, or change your TCU. Just flip the switch.

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May have to revisit the wiring as I don't yet understand the reasoning behind it. I know you can get shift kits for the AW-4 but I not quite sure about going into the transmission I've read with mixed reviews that the AW-4 doesn't like rebuilds

 

Sent from my SM-G935V using Tapatalk

 

You are referring to the power/comfort switch. When set in "comfort" mode the shift points were at a lower RPM and not as crisp. In "power" mode the shift points were raised to a higher RPM and shifts were a bit firmer. Most of us just set the switch in "power" mode and forget it. The HO change you are referring to was simply the elimination of the switch, and hard-wiring it to the "power" setting. If you have the switch (and it works), you don't need to "upgrade" anything, or change your TCU. Just flip the switch.

 

I think you're on to something!!

 

Power mode and TV cable adjustment should be done first.

The Power/Comfort switches are known for failing. Here is an alternative:

 

http://cruiser54.com/?p=435

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If you want to upgrade your AW4 shift points you can go with one of these https://www.summitracing.com/parts/trg-340-hd2?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-transgo-performance&gclid=CNfk5ITfsdQCFU9sfgodZMUPjQ. I installed it on mine and LOVE the way it performs, kick down is more aggressive as well as shift overlap but not so much that it is uncomfortable.

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May have to revisit the wiring as I don't yet understand the reasoning behind it. I know you can get shift kits for the AW-4 but I not quite sure about going into the transmission I've read with mixed reviews that the AW-4 doesn't like rebuilds

 

Sent from my SM-G935V using Tapatalk

You don't have to go "into the transmission"  but you do have to unbolt the valve body and separate it in 2 ,it's simple but extremely messy.The instructions provided are very well detailed and show where every check valve and spring goes just in case you drop one. I was able to do it in my gravel driveway in about half a day, the biggest pain the @$$ was trying getting to some of the bolts on the oil pan because of the exhaust and dealing with the stupid 2 piece dip stick for the transmission pan. 

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Thanks guys that's exactly the kind of feedback I am looking for. All of this started because I "lost " 1st gear but it would shift manually. I changed the shift solenoid but same results, now my shift cable,which is on the column, is messed up.

 

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Thanks guys that's exactly the kind of feedback I am looking for. All of this started because I "lost " 1st gear but it would shift manually. I changed the shift solenoid but same results, now my shift cable,which is on the column, is messed up.

 

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Have you tried another tCU?

 

You might try this. free and easy. http://cruiser54.com/?p=58

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Well new development. Made about 120 mile round trip in the Comanche today, went back to the truck for something and discovered the plug for the TCU hanging from under the dash apparently I didn't plug it back in after comparing the TCUs. Sooo I drove 120 miles with an unplugged TCU and I literally could not tell the difference in the shifting.

So NOW what???? Definitely don't understand the system have a lot of research ahead of me.

 

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