Transmission issues

First, what dang transmission is in a Sy? Some say a 700r4 while others say it is actually a 4l60. Which one is it?

Second, I think my TCC is not unlocking properly. I suspect the tcc lock-up solenoid is sticking. It locks fine but acts up while slowing down. I have heard that you can just unplug a harness to drive around without lock-up enabled to assist in trouble shooting before having to go into the pan. Is this possible and what/where is the harness plugged in at? Will this cause any harm for short term use?
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700R4 ... MD8 case ....4 wire pigtail on the drivers side

the 4l60 is in a M30 case .... 13/14 wire pigtail on the pass side
My trans has a connector on the drivers side. It has a 4 plug connector but I only have 2 wires going to it. Am I missing two wires? What does the wires run to? Everything on the truck seems to work sans the issue I described above.
its 4 pin connector .. it may not use all the pins

what color are the wires ?

you could just have a ground and the TCC lockup wire

I think I remember the wires being

My wires are hard to see but it looks like tan and gray, but could be a dirty purple.

I unhooked the harness and I'm going to take it on a short drive tomorrow and see if I still have the same issues.

Also, anyone know what the stock stall speed is for the Sy's. Just incase I have to get a new converter.
2100 on the stall speed

Is that the same stall as the regular s-series? Seems like it shouldn't be but Rock Auto shows the same GM reman number for both Sy's and regular Sonomas. They do show different numbers in a different brand though. Would a 2300 be good for the stock turbo or would I just be wasting money and/or rpm for such a small increase?


Active member
2100, I remember putting one in my typhoon and it was fine. Ran very strong. I had a fresh low mile typhoon transmission installed the old one was weak. This was years ago but the 2100 should be just fine. After the correct transfer of power I noticed the truck was very aggressive. It was also a cheap inexpensive converter I think it was 100 bucks.

DaveP's Ghost

Active member
All GM automatic transmissions were "re-named" in 1990 to more accurately reflect their attributes and torque capacity. The 700R4 became the 4L60. The "MD8" is the RPO for the 700R4 and the 4L60. The MD8 used in the SyTy and other trucks is the "K" case that has a bolt on aluminum cover and other strength enhancements.

The 4L60e (Electronic Controls) was introduced for the 1993 model year on trucks (Typhoon is the only <8,550GVW exception) and passenger cars for 1994. The RPO for the 4L60e is M30, which is cast into the case. I believe (my recollection is hazy), that there were K-case M30s with bolt-on covers, and non-K case M30 with sheet-metal covers.

The stall speed of any converter changes depending on how much torque is applied to it. The stock converter for SyTy IS the same converter and code (DEAF) as the "regular" S-series with the TBI 4.3. (The CPI engine, code DBAF, stalls at 2,050 RPM. This engine/converter was in the 92 Sonoma GT). SyTy stalls at about 2,100 RPM, but the TBI engine stalls at about 1,600 RPM. SyTy stock converters have little "7"s stamped between the dimples of the cover, are code DEAF on the decal, and the catalogue stall is 1654 RPM.

I once tried a DBAF (2,050 catalogue stall) in my bone-stock 92 red/gry because I had one in my stash, and thought it would be a "good idea". It seemed like the trans was "slipping" after the 1-2 shift, and acceleration was slower, because it was slipping and slower because of the higher stall. I went back to a DEAF (1,654 catalogue stall) and performance improved. I liked the lower stall better than the "slipping" higher stall. At least on the street where virtually all my driving occurs.

Sorry for the TL;DR, but there's good info in there if you bothered to read it.


Active member
I seem to recall Syclone #569 having some issues with his lock up function on his converter. He said he found some chafed wiring at this particular section of the harness... Not sure where this is located. Maybe Dave P knows.
factory splice.jpg


Donating Member
No Shit I was thinking the same thing reading this post. He knows his stuff and can remember it all Amazing!!!!!
After unhooking the plug and taking a few short trips the issue is gone so I think I have found my problem. I've got a TCC solenoid on order along with a fluid and filter change and hopefully that will fix the issue. If that doesn't cure it then I believe I will have to have a converter.

DaveP's Ghost

Active member
Gadzooks. Steve Gavic checks-in. You've been around a long time too. Do you still have your Typhoon? (Probably). I still have one of each, my Ty is still bone stock (but of course) and has a gillion miles on it, but is still capable of a cross-country trip with the hood welded shut.

There are a handfull of the Old Guard that still check-in from time to time, but activity is pretty low. Good to hear from you, friend.