My main question about this transmission is just how long can one
last? I have had to replace the 700R4 in a 1986 GMC pickup because of a
completely destroyed bearing, and am now looking at buying a 1984 suburban
that is pushing 200 000km, has hauled a trailer, and still SEEMS to be
doing fine other than some slightly eratic engaging of the torque
converter clutch. How long can I expect this tranny to last, assuming
that it has had regular fluid and filter changes, and had the benefit of a
1988 Chevy 1500
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The 1985 GMC Sierra transmission is a th700R4 overdrive transmission. The 700R4 does not utilize a vacuum modulator. Shift points are controlled by the T.P. or kickdown cabe. Proper adjustment of this cable is critical to transmission longevity. Your Pontiac, if originally equipped with a th400 transmission, has no means to connect this cable to the carburetor. I would not recommend this transmission swap. Also the th400 and the 700R4 use different sized drive shaft yokes, so your drive shaft cannot be used.
No there are different 700R4 transmission, well that not quite true. The 700R4 had many jobs to matted to Corvettes to SUVs, the internals are where the differences were in the 700R4 such as the servo's and boost valve which can be easily replaced. Best thing to do is to got to a Transmission shop that can build a transmissions for your Corvette or buy a replacement 700R4 for your year of Corvette. That is why the shift points and firmness are different in a Corvette then a Cadillac while they both have 700R4 in the 1990's. Be bad for a Corvette to shift like Grandma's Cadillac going to play dingo. Good luck and hope this helps.
GM is notorious for one size fits all, so most any 4x4 transmission will fit. I would stick to close years that can provide the same style transmission, like 700r4 or 4L60, so the electrical just plugs in. Hope this helps.
I assume you are disassembling to rebuild. A manual is your best bet. Haynes shows a GM auto trans manual,#10360. You could also look at faxonautoliterature. They have the original GM service manual for your truck, which would have a section on auto transmissions. They also list a GM trans rebuild book for that specific transmission. Hope this helps.
If the transmission has never been service "oil and filter changed" All the metal and dirt in the fluid may have caused the transmission to fail. There are valves and servo's that the fluid flows through and when dirt plugs up the passages or jams a valve open causing the transmission to slip slightly would make a transmission to fail. Check the transmission fluid level and condition and also check the transmission kick down cable from the throttle body. Good luck and hope this helps.
You may have two problems at the same time. The speed sensor is the easiest to replace. I would check and or replace the sensor. Then if the test drive shows the lock up fluctuating, I would replace the lock up switch in the transmission. Let me know if you have questions. Hope this helps. Rate me highly, please.
Hi. I have a '93 Chevy Suburban that is on the 3rd transmission. What you probably have is the earlier 700R4 transmission. What you should have is the 4L60E. I have done ALOT of research on these transmissions, and what I've found out is this: the 4L60E is essentially the same as the 700R4, with the exception that the 4L60E is completely controlled by the vehicle's computer. The 700R4 uses a more antiquated valve body with a TV (throttle valve) cable. In theory, you could use the 700R4 if you connect the TV cable and properly adjust it. If it's a 4X4, your speed sensor is in the transfer case, so that wouldn't be an issue. The 4L60E used in '93 and '94 will only work in those model year vehicles, because of the type of shift solenoids used. The newer units used pulse width modulation solenoids, as opposed to the older on/off solenoids. I have run my truck with the transmission unplugged and the engine still runs fine. The major problem with using the earlier 700R4as opposed to the correct 4L60E, would be emissions compliance. If you want to discuss this further, email me at firstname.lastname@example.org