Welp, never thought I'd actually sign up for a forums site, but I'm in DIRE need of help and just reading will only get me so far, so here we go as my first post. I have my 1994 Z28 with a 4L60E Transmission. Well, did. I absolutely COOKED the transmission in the most epic way possible (huge burnout at a show around here, worth it!) and now I need to replace it or rebuild it. I'm trying to see what other variations of the 4L60E I can throw in there that will work, even going as far as to see if the 4L65E, 4L70E, or a 4L80E are even remotely possible. But every time I try to get a straight answer from Ye Olde internet, I get mixed answers saying that 1994 transmissions go into 1994 Camaros ONLY, or 93 and 94 are interchangeable, or even only 93, 94, 96 and 97 are interchangeable. I'm stumped!

She's in the shop right now to get it looked at, I won't hear back from them until Monday, but they hinted at it being only swappable with a 4L60E from 94 only. Tech tried to do a test drive, and she dropped everything after 3 feet and said no. She would do the same to me, only liking 1st and 2nd gear. She would fight you and slip like crazy afterwards. She would attempt to shift into 3rd, rarely succeeding, but would slip mostly until put back into 2nd. 4th is out of the question. When she drops everything all together, it's the good ol' "everything is Neutral!" type deal. After sitting for 5 minutes with the fans on full speed and the engine off will the gears come back temporarily. (Thanks to Shoebox for the manual fan switch idea by the way, the previous owners wiring solution was so backwards, but I'm getting off topic here.)

I am open to second opinions please! As far as I have dug up that thing had never been flushed or rebuilt with the engine, so I assume this was a long time coming and I just pushed it FAR over the edge. 156K on the clock, bought her at 148K and have currently spent over 10k in catch-up repairs and maintenance. The engine itself runs fantastic after the repairs! Fantastic enough to destroy clutch packs on a stock trans unfortunately. On a side note, is the 1-2 shift always supposed to be so sudden and firm? No other shift is that harsh, even when downshifting. At WOT it would bark the tires, maybe this was a sign I was overlooking?

I know I'm asking a lot of questions, but I'm hoping for any answer I can get. Even if it's an answer I don't want to hear, at least it's a solid answer.

 

93 does not use a 4L60E. Uses a non-electronically controlled 4L60

94 uses a 4L60E that has a switched converter lockup, and requires a PCM programmed to control on/off lockup. No other years have that.

95 uses a 4L60E that has a pulse width modulated (PWM) lockup, and requires a PCM programmed to control PWM lockup. While all subsequent years are PWM lockup, the trans internals are not compatible with the 95 PCM. Trans wiring has more pins in the connector than 94.

94 and 95 have the same PCM part number, so if you found a 95 4L60E you could have your 94 PCM reprogrammed and modify the trans wiring harness.

Here's the best explanation available:

4L60E year differences and interchanges.

Have you scanned the PCM for transmission codes?

Good source of rebuilds:

https://cahallperformancetrans.com/

 

So the shop was mostly right. Only transmissions from 94 for my 94 then, UNLESS I do some modifying for a 95? That sucks, but I'll make do. I thank you for that confirmation.

On the other hand, those performance transmissions Cahall has are very reasonably priced! Only wish I could install them myself as I do not have a garage nor the resources unfortunately. Any shop I go to refuses to install customer bought parts which is also a big pain in the butt.

I have not scanned the PCM yet, I should've done that before I sent it in. I do have an ALDL cable from Red Devil River I can hook up to a laptop to use Scan9495 with. I'll do that when I get the chance.

Are their adapters available for the 95 to 94 trans wiring harness? If not, is making one any difficult?

 

As far as I know, the 94 has a 11-pin trans harness connector, 95 has a 12-pin connector and requires an additional wire run from the PCM to the trans, plus the new connector. You can compare the 1994 wiring diagram to the 1995 in the respective factory service manuals. Free downloads here:

https://www.mediafire.com/?40mfgeoe4ctti

 

Thanks for that link! I was hunting down a manual like that.

I've heard back from the shop, they found a remanufactured transmission for my car and it comes with a torque converter. Price in total including labor is around $4,300. Stings, but I can manage that.

Are remanufactured transmissions good, if not, better than rebuilding one? As far as I've heard it's better than a used one.

 

A reman is better than used--by a long shot--but if you can find a good rebuilder, even better. Then you can specify what extras/upgrades you might want (upgraded sun shell--known POF in 4L60e; dual cage fwd sprag; upgraded 3/4 clutch pack w/ 7+ frictions--another known POF; corvette servo; etc.). You'll also want to specify OEM (ACDelco) shift solemoids. If you do a search for "4L60e rebuild options" you can get a lot of info.

I'm guessing you already made the call on this--been almost a month--but $4300 for a reman is pricey. I had a high-end shop rebuild mine not long ago, got the upgrades I note above & only had to lay out $3100 (incl the TC). And it's tight-- ~100 RPM shift points. Maybe your reman has lotsa upgrades--dunno--but I'd want to know who did the build, what they did, what parts they used, etc. before laying out that much $$. Hope it works out for you.

 

Your reply timing is nothing short of comedic. They called me today to let me know they had JUST gotten the old transmission out, and the new one into the car. It's been a bumpy road as well, as it recently got broken into while at the shop! That's a whole fiasco I'm dealing with separately, so I won't dive too much into that.

I'm noting those POF you mentioned for later. I'm gonna ask the shop a few things once all the work is done, mainly where the transmission is from, is it rebuilt, does it have engineering updates, reinforcement, etc. Then I'll ask if they can dissect the old one to see where it failed exactly--I'm guessing clutch packs--and if THAT one was upgraded and/or modified as well. They will most likely say no to that request, but it's worth a shot. I'm definitely going to baby this one for a while, at least until I can scoop up enough to have those POF prevented/fixed, and some decent upgrades done to it. I've also read something about the 4 gear planetary set for a 5 gear? is that just a reinforcement or is that another POF? And you might be right, given the price even without the labor, it sure seems like this thing has to be at least beefed up a bit, even if it's by a small amount. A 30 year old transmission selling for this much, if original and kept strictly OEM, would be a heck of a gouge!

I asked this earlier and I hope you can also add some insight to what she did beforehand. Is the 1-2 shift always supposed to be so sudden and firm? No other shift is that harsh, even when downshifting. At WOT it would bark the tires shifting from 1st to second, revving all the way to 6,000 RPM. No, the engine isn't stock, and I don't know what the PO did to it, all I know is that she pulls like a mule hopped on Monster Energy.

 

This link will provides some useful info w/ diagnosing & rebuild options on a 4L60e:
https://www.gmtransmissionparts.com/...-buyers-guide/

But you're kinda behind the curve on this, seeing how it's already been replaced. The shop that put it in prob can't tell you what's in it (they didn't do the reman), but they can tell you who rebuilt it. Did they include the build sheet? They also likely won't tear down your old unless you pony up more $$. (Btw, what happened to the core? Did they return it to the builder? If so, that should have brought the cost down some.) It is unwise to assume that since you paid significantly more, there must be significant upgrades. Whle that might be the case, you don't have anything to substantiate it. Assume only what you get in writing. Btw, did you get any warranty on this?

This underscores the need to do your homework first, find a reputable builder, tell 'em what you want based on what you want to do w/ the car, your driving habits, etc. (a good rebuilder can offer some pointed suggestions) & let 'em do the deed start-to-finish. In my case, I got the upgrades I specified, and was @ the bench when they did the tear-down. Lotsa folks told me to get the high-stall TC, but when I discussed it w/ the rebuilder--based on what I wanted to use it for--they said I'd be better off w/ an 1800. A tranny is a major expense, so being well informed before you do anything is a wise move.

 

Well, I've finally got it back, and holy moly was it a massive difference. They hooked me up with the good stuff, REALLY good. Everything behaved so differently to me and the shop gave me a rundown on WHY it was different.

The shop WAS able to tell me what was inside the new transmission--mainly updated/better clutch packs, addressed POF some of what you mentioned, and a much more efficient/stronger TC--and from that they were able to tell me what warning signs I had completely overlooked. The TC was apparently not locking when it should, hence it would hunt for RPM at highway speeds. The shifts were harsher than they should've been (my question finally answered) and was not a good sign. Trans fluid temp was climbing faster than it should've been even when stationary, and the engine was revving unusually fast upward and downward, instead of the slow decline of RPM it's supposed to have when revving it in Park and Neutral. Still sounds great! Thank the Flo~Pro muffler for that.

I would've done my homework on this further if I had a more reliable backup ride, but that's a separate issue. Plus, no good rebuilders near me funny enough, body shops galore though!

Yes, they gave me a full warranty, without question. After the break-in period of 500 miles, I will be taking it back to have it flushed while under said warranty. Since this new one has a TCM (Transmission Control Module, did the old ones have those too?) I have to teach it how I drive, for possibly thousands of miles they said. No big deal, I love driving that thing anyway!