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Stickied: Lets walk through the differences between '94,'95,'96 and'97 4L60E's

142K views 78 replies 39 participants last post by  Marky Dissod 
#1 · (Edited by Moderator)
Moderator note 3/14/2022: This thread was written by the late Frank Cahall of Cahall Performance Transmissions of Newark Delaware. His wife Gail Cahall is still running the business as of 2022. Some people (including Frank) make a big deal about the 3-2 downshift solenoid change for '96; others have swapped and not had a problem. I am preserving this thread for the content it contains.
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None of the '93 -'97 4L60E's are directly interchangeable, except '93 and '94!!! Here's a list of yearly differences that will show you why. Yes, some years will fit in others and may not even throw a code, but there will be an issue in the long run. The big issues become forced 3-2 downshifts, converter lock-up issues, and burnt lock-up clutches. When a converter clutch cause it to lose lock up, the 3-4 clutches, in the transmission will soon follow because the 3-4's need lock up to keep them cool while cruising in overdrive.

1993: These were used in trucks only. Not available in F-Bodies, B-Bodies, or Vettes

1994: Interchangeable with '93 4L60E with no modifications. The '93-'94 is a NON-PWM transmission. This means that the lock-up apply strategy is an on /off arrangement. It has an 11-pin case connector. Does not have PWM cast into the front pump. 1 piece TCC control valve in the valve body. The plate has holes in the plate, marked in the diagram below. 1st design 3-2 valve

1995: Stand-alone year! Will not interchange with any other year. This is a PWM transmission. An extra solenoid was added to the valve body to control the pulsed lock-up strategy of the converter clutch. It has a 12-pin case connector, an extra wire in the transmission to the computer harness, and a different computer to control the new PWM circuit. Has PWM cast in the front pump? Front pump internal passages are different to match the new TCC strategy. 2 piece TCC control valve in the valve body. Has holes in the plate, marked in the diagram below. 1st design 3-2 valve. 12-pin case connector. '94 computer won't recognize the new TCC strategy., and will burn the lock-up clutch and 3-4 clutches up. '96 computer isn't compatible with '96 3-2 control solenoid.

1996: The 3-2 downshift strategy was changed to an on /off arrangement. The TCC control solenoid was changed to a 20-31 OHM solenoid, from the previous 10-15 OHM solenoid. The 3-2 control valve was changed to the second design valve. The easiest way to identify the valve is, the second design valve will fall out as soon as the solenoid is removed. The first design has a plug and retaining clip. TCC solenoid remains 10-15 OHMs, which is the same as the '95 arrangement. Has PWM stamped cast in the pump. The pump is the same as '95. Will not interchange with '95 unless changing 3-2 solenoid, valve body casting, and separator plate. Has holes in the plate marked in the diagram. '94 or '95 computer will not accept the 20-31 OHM 3-2 solenoid and will throw an SES light and throw the transmission into limp mode. Some less knowledgeable builders will swap the solenoid so the computer will see the correct resistance, but the valve itself then causes downshift issues. If only the solenoid is changed, it will result in a 3-2 downshift cut loose. In other words... a 3-neutral-2 downshift. Speedo moved to the passenger side of the tail housing but easily changed.

1997: Basically the same as '96.

Frank
 
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#2 ·
Finally something interesting to read on ISSF!

It has been a while. I really enjoyed the other thread too!

FYI, on the B bodies, the speed sensor was moved in 1996.
 
#4 ·
...... When a converter cluych cause it to lose lock up, the 3-4 clutches, in the transmission will soon follow because the 3-4's need lock up to keep them cool while cruising in overdrive.
.......
Frank, can you explain that one a little more. How do the 3-4's generate heat while cruising in overdrive? Plus, my understanding is that fluid flow through the cooler is reduced when the TCC is locked. It's no mystery that fluid temp will rise without TCC lockup, but why specifically the 3-4 clutch pack?
TIA.
 
#6 ·
Frank, can you explain that one a little more. How do the 3-4's generate heat while cruising in overdrive? Plus, my understanding is that fluid flow through the cooler is reduced when the TCC is locked. It's no mystery that fluid temp will rise without TCC lockup, but why specifically the 3-4 clutch pack?
TIA.
Pat, if you look at a fluid chart, you'll see that lock up changes fluid routing. This is neccessary for the 3-4 clutches to stay alive during cruising in O/D. If you've ever built a non lockup 700R4, you'd understand it a little more. They actually sell a "non lockup valve for them which changes this fluid flow through the valve in the pump without it having to be applied. This isn't a myth. We learned a long time ago that if a 700 / 4L60E loses lock up, the 3-4's will follow very shortly.

Frank
 
#6 ·
Not arguing here, just discussing, trying to make the connections in my own head.
I'm still having problems with two things:
1. Where is the heat generation coming from in the 3-4 clutches when cruising? there should be no slippage going on to do that.
2. For the TCC failure to cause a fluid routing problem, I assume you must be talking about a failure of the mechanism (either in the TC or in the valvebody), and not just a TCC friction material failure as I think most of us assume. correct?
 
#7 ·
when an O/D transmission has a ratio greater than 1:1m it obviously brings engine RPM down. It will often do so enough the the sprag in the converter will start to unlock, thus generating more heat. With the converter locked, this isn't an issue. The 3-4 clutches are the first area to show the danage caused by the excessive heat. This may be aided somewhat in vehicles with a 3.73 or lower gear, because RPM's won't drop enough to cause the sprag issue in the converter. When I explained all this, previously, I was basing things on a stock vehicle. Using the wrong year will still burn the converter clutch up, and will still aid in future failures. A slipping converter clutch is still going to generate heat, and then begin to shed metal or debris into the transmission.

Frank
 
#13 ·
I was pointed here do to the swap I am about to do and maybe you could help?

My 1994 Buick Roadmaster Wagon was T boned and I found a 1995 Chevy Caprice wagon that needs a motor.

So going to put motor in which is not the issue. My 1994 Trans was just inspected and great shape serviced and synthetic fluid and I want to put it in with the motor into the 1995. Condition of 1995 trans is unknown?

I can re-flash the PCM or take PCM from 1994 to 1995.

So putting a 1994 B body trans into a 1995 B body is there going to be wiring issues?
 
#14 ·
I was pointed here do to the swap I am about to do and maybe you could help?

My 1994 Buick Roadmaster Wagon was T boned and I found a 1995 Chevy Caprice wagon that needs a motor.

So going to put motor in which is not the issue. My 1994 Trans was just inspected and great shape serviced and synthetic fluid and I want to put it in with the motor into the 1995. Condition of 1995 trans is unknown?

I can re-flash the PCM or take PCM from 1994 to 1995.

So putting a 1994 B body trans into a 1995 B body is there going to be wiring issues?
This won't work. Your '95 computer is going to be looking for a PWM solenoid on the transmission that isn't there. This will throw it into limp mode right away.

Frank
 
#17 ·
Well I think changing the complete harness would be a lot of work!!!

But I have been comparing wiring diagrams from my 1994 Service manual and some 1995 wiring diagrams online.

They are literally identical including the page number, except for one extra wire used in 1995 trans for the TCC PWM control solinoid. So I do beleive if the plug for trans is 11 pin on 1994 and 12 pin on 1995 I can swap plugs and not use the extra wire... plug in my PCM and be good to go?
 
#19 ·
Not if I change the PCM to the 1994 too!

I know my 1994 trans is good, I don't know anything about the 1995 trans...

I've spent hours going over the 94, 95 wiring harness from PCM, pin by pin and other than that one wire you pointed out for trans PWM TCC, I can't find anything differant?

Comparing the bin files for the PCM there are changes everywhere in 4l60e from Impala SS 94 to 95, hardly anything set up the same...
 
#20 ·
Not if I change the PCM to the 1994 too!

I know my 1994 trans is good, I don't know anything about the 1995 trans...

I've spent hours going over the 94, 95 wiring harness from PCM, pin by pin and other than that one wire you pointed out for trans PWM TCC, I can't find anything differant?

Comparing the bin files for the PCM there are changes everywhere in 4l60e from Impala SS 94 to 95, hardly anything set up the same...
Yes, you can use the '94 computer. You won't have to change the harness.

Frank
 
#23 ·
I've got a question for you guys. I'm about to purchase a new transmission, either brand new or rebuilt, and I'm a little worried after reading this.

Do I go straight to the transmission to find out which exact version I have, or can I go off of the options tag on the trunk lid?

The only reason I ask, is because my '95 was built 9/94. I know that my car has the older transmission code in the computer, because it has always started from second when I select it. It will only drop to first when I completely bury the throttle...

Also, how do I know for sure that the shop that builds/rebuilds the trans, knows about all of these differences? I'm probably going to swap this one myself, and I'd hate to have to do it all over if there's a failure.

By the way, I know the trans is original. I bought the car in 97 with 35k on it.
 
#24 ·
A competant transmission builder will know what you need. Your car is a '95. Only a '95 transmission will work. MOST transmissions you buy will be rebuilt. You won't find a NEW 1995 4L60E. Because of this, it's best to have your original rebuilt. Keep in mind that MANY shops don't even know the difference between a '95 and a '96. I've went behind too many shops that have mixmatched these years and put a Band Aid on a bullet wound by changing the 3-2 solenoid so the computer sees the correct resistance. The problem is, the valve body is different, so changing the solenoids will create other issues. Even if I build a core for a customer, I ma ke certain they get the exact year that their car is...No cutting corners and just trying to sell them whatever I have laying around.

Frank
 
#25 ·
Ok, I have a 96...I bought a used built trans out of another imp and took it apart for a refresh, Im doing all this myself ...My valve body is stamped 95..Im told thats the issue between the trannys...I was told that this still may be for a 96 but there are ways to tell between the 95 and 96 valve bodys...How do I knw? What do I look for? Thanks
 
#26 · (Edited)
Ok, I have a 96...I bought a used built trans out of another imp and took it apart for a refresh, Im doing all this myself ...My valve body is stamped 95..Im told thats the issue between the trannys...I was told that this still may be for a 96 but there are ways to tell between the 95 and 96 valve bodys...How do I knw? What do I look for? Thanks
The '93-'95 valvebody has a 2 piece 3-2 control valve. On a '96-up valvebody, if you take the 3-2 solenoid out, the valve behind it will fall out. On an earlier valvebody, the valve is held in by a plug and a retaining clip. If you go back to my plate diagrams in this thread, you'll see a hole marked '93-'95, at the top left corner. That hole will not be in a '96-up plate.

Frank
 
#27 ·
I have read this sticky and was wondering if you could answer this question.

I had a 96 9C1 that I did the OBD2 to OBD1 conversion. A few year later lost reverse and end up replacing it with a trans out of a 95 9C1. The only change made was replacing the tail housing for the VSS.

Never had an issue with trans even swapping a 2800 stall TC to a 3400 stall. Drove the car on the street and race it.

If 95 and 96 are not interchangeable, how come mine never had a issue?
 
#28 ·
I have read this sticky and was wondering if you could answer this question.

I had a 96 9C1 that I did the OBD2 to OBD1 conversion. A few year later lost reverse and end up replacing it with a trans out of a 95 9C1. The only change made was replacing the tail housing for the VSS.

Never had an issue with trans even swapping a 2800 stall TC to a 3400 stall. Drove the car on the street and race it.

If 95 and 96 are not interchangeable, how come mine never had a issue?
You can use a '95 computer with a '96 trans without throwing a code. It will cause 3-2 issues in most cases. a '95 trans with a '96 computer will throw a 3-2 solenoid code.

Frank
 
#29 ·
Well looking for another tranny just got more fun
since 95 is a standalonecwm3
 
#30 ·
Frank, I plan on pulling my probuilt out of my 95 B4U and installing into my 94 9C1, can I just use the PCM out of my 95 B4U? If not is there a way to convert? Thanks, Tom
 
#34 ·
Thanks Frank! Got the 94 harness yanked out, grabbed the 95 harness 1st thing I noticed was the ABS was different. The ABS in the 94 hopefully will work fine,but I'll have to program out the ABS in the 95 PCM. Engine looks funny without harness, lol.
 
#35 · (Edited)
help!

Great thread! I have a ? That I dont think has been covered yet. I have A 95 Caprice with police package. the original trans is not rebuild-able due to case damage. is any 95 trans ok? or does it need to be out of a 95 with LT1 engine? already went through two other transmissions B4 I found this thread and im tired of wasting $$$$ on an awesome car!:confused: TIA

OH NO!!!! just saw it said "banned" under CAHALL! is he not on here anymore? I tried to send him an EMail also. any info or a way to get in touch with him would b appreciated! I love this car but Im putting way to much $$$$ into trans problems.
 
#36 · (Edited)
Great thread! I have a ? That I dont think has been covered yet. I have A 95 Caprice with police package. the original trans is not rebuild-able due to case damage. is any 95 trans ok? or does it need to be out of a 95 with LT1 engine? already went through two other transmissions B4 I found this thread and im tired of wasting $$$$ on an awesome car!:confused: TIA

OH NO!!!! just saw it said "banned" under CAHALL! is he not on here anymore? I tried to send him an EMail also. any info or a way to get in touch with him would b appreciated! I love this car but Im putting way to much $$$$ into trans problems.
It was right there next to this sticky

http://www.impalassforum.com/vBulletin/showthread.php?t=232098
 
#38 ·
Excellent sticky worthy thread. I had no idea the transmissions were not interchangable throughout the years they were used.

Thanks for posting!
 
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