OK, sorry if this is in the wrong forum bit it seems logical to me to start here, so please don't flame me if I am wrong.

I have been doing some work on my '88 IROC drivetrain and ECM/Memcal that I have in my '87 el camino, so I have gotten somewhat profecient in making the changes and burning chips.

I have the Tunercat and $32b def file, for this would like to not have to spend too much more $$$.

I have a '90 IROC convertible and the 2.73 rear (drum brakes) has some issues, mostly bearing noises. I have an '89 3.23 disc brake rear and am considering installing it in my car. The mechanicals are one thing, but to make changes to the ECM so that the lockup on the torq converter is where I would like some advice.

If I go this route to change out the rear, what ECM should be on my '90 and does it use the MEMCAL type setup like I have in the '88?

The motor (LB9) is pure stock and I was wondering if I just could get a stock chip for the setup, even though they never made that setup ('90 LB9, auto trans, with 3.23 rear). Seems to be the easiest but not sure what chip code I would be looking for? Otherwise then I have to look into modifying the chip that is in the ECM, which is more work.

I would really like to swap out the 2.73 drum rear to the 3.23 disc brake rear, but this might be just too much work with little return.

Opinions and feedback please!

Bruce

 

Need to change the speedometer gears in the transmission. This way both the speedometer and ECM have the proper MPH showing. See the transmission board sticky's here on TGO. There is one for 700R4 speedometer gears.

Once the 3.23 rear is in, you can make changes to the TCC lockup points. But this is mostly a user drive-ability preference.

Of course, if you don't care if the speedometer is correct, there is a VSS PPM value for the magnetic input in the ECM's calibration. Can tweak this until the ECM has the correct MPH.

RBob.

 

Here is a link that may help you can use there calculator chart to pick the correct drive and driven gears.

http://www.transmissioncenter.net/sp...n_______va.htm

 

Thanks for this feedback. I was including the speedo gear in with the "mechanical" portion.

Any idea if the ECM on my '90 is a 7165? Assumming so, then it has the same type MEMCAL, thus the physical portion of this would be the same?

Then next question is what is the definition file, $32b??

Any ideas?

 

The ecm on your 90 tpi speed density is a 1227730 $8d, the memcals are different size and definition from maf to sd and the sd has the knock module attached to the memcal. The $32b mask is use with the 1227165 maf tpi from 87-88.

 

Thank you very much. This is exactly what I was looking for.

Any idea if they made a stock chip for my LB9 motor with the 3.23 rear?

 

You can still order The Axxb gm / acdelco 16163062 I bought one a few months ago for $110.

 

http://www.ebay.com/itm/ACDELCO-OE-S...#ht_1187wt_931

 

According to the tech data here the '90-'92 LB9 was never factory equipped with 3.23 gears. So no, there isn't a stock calibration for your set up.

RBob.

 

So then, the AXXM is not for the 305TPI with 3.23 rear?

 

attm ? there was not a gu5 option in 90-92 the axxb would be for 2.73 I believe

 

Sorry, meant AXXB.

So the AXXB is what I should have now?

I'll have to pull the ECM this weekend and check it.

 

There are a few for a lb9 automatic 90-92 and even some superseded ones.

AXYD,ANHY,ANJB,AXXB,AXXF,AWFU,AWFY,ATNY,AWLT,ARZU

 

Does anyone know what each of these are for?

Any of them fit my application with the 3.23 rear (LB9 motor)?

 

http://www.gearhead-efi.com/BCCFind/

89 was the last year of the 3.23