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More power for your 87 and 88 Renix 4.0

C

cruiser54

NAXJA Forum User
Location
Prescott, Az
Confirmed over the weekend the difference in ECUs used on Renix 4.0s.

I was sure there was a difference but I used my neighbor as a guinea pig with his 87. I let him use one of my 89 to 90 ECUs as long as he installed it.

He came back from the test drive smiling from ear to ear.

Last night he installed the later model Renix TCU, I'll have a report back in a day or so.
 
The 87 put out 173 horsepower, the 88 put out 177. 89 and 90 put out 182. Only difference is the ECU. I've been doing this for years but it came back to me how much difference it really makes when I let my neighbor put the ECU out of my 90 parts Jeep into his 87. I downplayed the benefits other than it's newer. I let him drive it and report back. He was extremely pleased.
 
I snatched a 90 ECU today.

We should put together a list of numbers.

This one was an 8849
I can get the numbers off the 87 in my old MJ.
and the numbers off the new 90 MJ.
 
8953005428 auto
8953005429 manual.

I'm anxious to see what other numbers you guys come up with. There is a "year date" code also. Let's keep track.

Auto trans ECUs can be used in manual trans vehicles, but a manual trans eCU can have idle issues in an auto equipped one.
 
I replied in the OE tech post, but this seems even more relevant here.
I grabbed a '90 ecu from the junkyard for my recently acquired '88 xj. It did not have the expected part number on it, instead it had #56006078. It was out of a very late production '90(door sticker read 08/90-I believe), 4.0/aw4/4x4......And yes, it WAS a renix. :laugh:
Now, my '90 mj has #53005429, just like you would expect.
I haven't really been able to find the 6078 computer talked about anywhere.
I'll report back after I swap it into the xj, sometime in the next week or so.
 
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yep, the mj is a manual trans.
the other one i pulled from the junkyard i grabbed because half the dash was already pulled by someone else, so easy access.
when i got it out and saw the "different" part number, i checked the production date, which was around 8 or 9 of '90.
i'll see if i can get other numbers off it, just for future reference.


cruiser54 said:
429 is the one I'm familiar with. Manual trans, right?

The ECU has a build date o it also.
Click to expand...
 
Hellbent said:
yep, the mj is a manual trans.
the other one i pulled from the junkyard i grabbed because half the dash was already pulled by someone else, so easy access.
when i got it out and saw the "different" part number, i checked the production date, which was around 8 or 9 of '90.
i'll see if i can get other numbers off it, just for future reference.
Click to expand...

We can Google the number off the junkyard find.
 
More info... The 56006078 computer has no numbers or letters preceding the part number like the others. It has a small white paper sticker ink-stamped with ”9 0 1 6", and underneath the word "BENDIX", it has a part number S101140203B.
 
Yeah, the SF and 89 at the beginning of the part mean nothing. That's a time when Jeep and Chrysler were blending part number systems.

9016 means 1990 for sure and maybe January 6th?
 
Cody reported back last evening on changing his TCU from the standard 87 model to an 89 model I had from a parts Jeep.

Better shift points with less lugging and definitely noticeable.

I knew they changed the TCU after 87 due to customer complaints, and 88 and later seem to work great. My wife's 88 shifts like my 90.
 
Hellbent said:
yep, the mj is a manual trans.
the other one i pulled from the junkyard i grabbed because half the dash was already pulled by someone else, so easy access.
.
Click to expand...

same reason I grabbed this one, plus ShortXJdoug needed on to troubleshoot the odd behavior of my old 87.

Seems I should have grabed the TCU for someone as well.

I may go back to that XJ in another two weeks and snatch the cruise control stuff, so maybe I'll grab it all.

Was curious if auto cruise control stuff would work with a manual, provided I could tie in the clutch switch. I assume the pins are there in the controller. I haven't researched it yet. Never wanted cruise in my 87, but kind of want it these days in the new one.

Edit: I will get the numbers off the one I pulled the the day, it came from a 90 limited auto.
 
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99% sure the last 2 digits are the week ofbthe year. The one I have coming is 9020 and the JY guy said the jeep vin showed it was made in 5-90. Got to be a winner with the date of 5-90:)

If I can pick up another 12 or so HP after my present mods: 4:56 gears, Borla header, 2.5" exhaust, 60mm TB, Mustang injectors, I will be super happy!!
 


Much to my surprise, I looked under my dash and found this......... That's not from 88. Makes me wonder why it was replaced and what else I need to worry about

Edit: after looking around, it seems like this was a general mopar replacement for the renix ecu in general so there's no telling :( could be a good or bad year not sure
 
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