someone972

iTrader: (2)

I'm planning on rebuilding my 700r4 as it has been slipping for some time, but before I get too deep I wanted to get some opinions on whether I will run into problems or not.

I do not know much about the history of the transmission. I'm not even sure if it is the original transmission for the car. If it is, then it has around 150K miles on it (once again, unknown if it has ever been rebuilt).

The good:

• Shifts through all gears, seemingly at proper points.
• Does not make any majorly concerning sounds.
• Lockup works.
• Did not have any metal shavings in the pan when I bought it, but could have been cleaned by PO. Probably should check this again at some point.
• On the occasion that I WOT, it downshifts fine and seems to shift up ok.

The bad:

• Slips - most noticeably during the 3-4 shift the RPM raises briefly. If it slips much during regular driving besides during the shifts I don't notice it.
• Fluid which I replaced sometime in the last year seems fairly dark and burnt by this point (presume it's due to the slipping).
• Lately, only when cold, it does not seem to lockup the converter at the same point that it usually does (has to have higher mph before it will eventually lock)
• Occasionally the car feels like it's bogging a little and the rpm drops a tad (does not seem engine related), especially when hot.
• At very specific speeds/throttle positions it on rare occasion has issues. For example, it once felt like it was either rapidly slipping and catching or shifting gears for a few seconds until I changed throttle.
• May have seen some abuse from previous owners.

Another strange behavior is that it sometimes feels like it "frees up" accelerating from idle under certain conditions that I can't pinpoint (although higher throttle seems to help?). Also, it may be my imagination, but it seems to shift and run overall better for a while after a WOT run.


What I'm most concerned about is having to replace many hard parts. I would be getting one of the rebuild kits from Pro-Built, so things like clutches/bearings/seals/steels will be replaced, but I'm concerned with the slipping that the pressure plates will be discolored and too toasted to be usable, or the bushing-touching surfaces will be overly worn, etc etc.



I'm sure many worse transmissions have been brought back to life, so hopefully someone can give me either some peace of mind or talk me out of rebuilding it .

jmd

iTrader: (4)

Sounds like a great candidate so far.
88-93 are the "better" 4L60/700-R4 years. 93 has a unique TCC plug.
I'd review the tag / stampings to verify it's a 88-up core and proceed as planned. There's also the valvebody differences to identify; search auxiliary valvebody.

Engine temperature as seen by ECM by the sensor is one factor in the TCC lock-up algorithm. I drive about 3-4 miles before mine kicks in (4bbl ECM though) even in warm or hot weather, so you might see similar. It's easy to tap into the wiring with a test light and see if the ECM is commanding it at a certain point. It's possible to short two wires at the ALDL to force lock-up as well.

someone972

iTrader: (2)

Thanks for the input! Found the tag on the passenger side of transmission near the rear, right above transmission pan. Reads 1FTM344A. Breakdown for those interested:
1 - 1991
FT - Model
M - 4L60
344 - Built 344th day of the year
A - First shift of the day.

Looks like the FTM has wiring for the TCC lockup with a 4th clutch switch and another switch labeled "TEMP" which I presume is temperature?

I guess that it actually might be the same transmission that came with the car, based on that info. Are there any known issues with this model of 4L60 or did they work most of the kinks out by now? Also, should I still try and find what the AUX valvebody is, or can it be determined by the model number (and how important is it to know what it's got anyway?)

articwhiteZ

iTrader: (56)

that's a good one to work with. with the right parts ya can get that thing to hold 700+hp all day long.

5 pinon planets
beast sun shell (a real one with pat # stamped on it)
auto / manl valve body (b&m makes a good one)
front planet drum bolt on retainer. not clip.

jmd

iTrader: (4)

You got it figured out based on tag. If missing, Aux valve-body identifies as the later version you want. Auxiliary valvebody was in some 87 and all 88-up versions. ID info here: https://www.thirdgen.org/forums/tran...y-vs-late.html

JHX

Hard parts are where the money is. (Just like an engine rebuild, you buy the cheap stuff in the "kit")

The good news: All the heavier duty 4L60E stuff will retro to your trans. There's no need to discard it.

The bad news: You have to tune it "old school"

No fancy laptop stuff here.

JHX

If you don't have specialized knowledge here? You should take it to a professional.

It's too bad you're so far away.

But, seriously.. If you don't know what you are doing, you will waste a lot of money.