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Mike S.
Mike S., Chevy Mechanic
Category: Chevy
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Experience:  ASE Certified Master Technician
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a 1991 chevrolet g20 van with a 700 tranny.

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I have a 1991 chevrolet g20 van with a 700 tranny. I just got another tranny from the junk yard. Installed it and took it for a test drive. Next day it will not shift into any gear. Please help
Submitted: 3 years ago.
Category: Chevy
Expert:  Mike S. replied 3 years ago.
First of all check it for a fluid leak. Check the fluid level and also look and smell for burnt fluid or a brown fluid. If everything is ok, next I would drop the pan and make sure the filter is both still attached and it is not clogged up with debris that may have fallen off the clutches and gathered in the pan.
Customer: replied 3 years ago.
It will not shift. It just revs up. I checked the fluid and it still looks brand new. Does it matter if it is a little over the fill line on the dip stick? Is not changing the torque converter the cause of the problem?
Expert:  Mike S. replied 3 years ago.
It should not matter if it just a little over the full mark. What was the problem with the old transmission, did the engine rev high and no movement as well from the tranny? If so, you may have a bad torque converter.
Expert:  Mike S. replied 3 years ago.

Do you still have that old tranny? If so look at the filter. This picture shows red color is pieces of converter clutch material.

 

700 Pictures

Pan & Filter

Left - The red color is pieces of converter clutch material

Right - Notice black chucks of clutch material

Both are indications of a failed transmission. Even if the transmission still moves, a rebuild is needed.

http://www.donneysaab.com/FDT/700techpics.html#PanDebris

 

Customer: replied 3 years ago.
The old tranny shifts but I have to rev the engine up real high to shift. I did not change the torque converter, the original one is in the original tranny. I just swapped out the whole tranny for tranny. The old filter looked brown and the magnet on the bottom of the pan was full of stuff. The old pan was darkish brown color.
Expert:  Mike S. replied 3 years ago.

You may also want to do a pressure check to see if the pump is actually supplying any pressure. If none at all the pressure-regulator valve may be bad. If little or low the seals on the pump may be bad. If the pressure is ok, then it may be the torque converter. There should be a small pipe plug on the side of the tranny, you will need a pressure gauge that will read up to 300 psi. Rev the engine to 2,000 rpm and take readings.

 

Range Minimum Maximum
Park90-110 190-230
Reverse95-120 200-300
Neutral90-110 190-230
Overdrive90-110 190-230
Drive90-110 190-230
Second185-230 185-230
Low185-230 185-230

Expert:  Mike S. replied 3 years ago.
It sounds as though the clutches were burned up in the old one. I would overhaul that and keep it. Plus, I would swap out that torque converter.
Customer: replied 3 years ago.
Is the pressure regulator valve in the tranny? The filter on the newer tranny looked fine and the newer oil pan was so much cleaner. Are you telling me to keep the newer tranny and get the other torque converter? Or keep my original tranny and switch out the torque converter?
Expert:  Mike S. replied 3 years ago.

Yes, the pressure regulator valve is part of the pump. I am saying since from what you said you did not swap out the torque converter from the old tranny and out in front of this tranny, so I am assuming this torque converter may be the problem. Usually you can tell when the torque converter is not converting any torque is when you place the shifter in drive and rev the engine up, the engine will rev high and the vehicle will not move at all or very little. If the torque converter was good, the engine would not rev so high because of the extra load that turning the transmission and attempting to turn the rear wheels would have on the engine torque.

I was just saying to rebuild that old tranny, since a rebuild kit might only cost $100 or so.

Expert:  Mike S. replied 3 years ago.
Plus, I meant to look at the filter on the old tranny to see if there were any signs that converter was bad, but nevermind cause the question is is the torque converter in this new tranny any good.
Customer: replied 3 years ago.

OK, just to confirm I understand: since the newer tranny's oil pan had no sign of burnt oil and looked better then the original one, I should keep the newer tranny and switch out the torque converter. Correct? I did not change out the torque converter, it still has the original one in it. Does it matter that the newer tranny worked after I installed it and took it for a test drive, but then wouldn't shift after that one drive?

Expert:  Mike S. replied 3 years ago.
Correct! Did you get any kind of guarantee with this tranny and converter? Yes it would matter. It did work then all of a sudden it did not? Does it seem to go into gear just a little? If not make sure the shifter linkage or cable is still hooked up. Did you hear any noise or anything right before it stopped working? I don't think a converter would just go bad that quickly after it was first working. Craw under that van and take a look around to see if everything looks ok. Look for a massive leak or lines that may have come off. Make sure the driveshaft is still in one piece. Can you move the van in neutral if you push it?
Customer: replied 3 years ago.
Yes it can be pushed with the engine running and in neutral. When I took it out for the test drive, the newer tranny shifted, but shifted slowly from gear to gear. But that was better then the original one. When I run the engine now and go from gear to gear, I do not hear any change. So what I'm saying is: When I put it in any gear, it all sounds the same. When I rev up the engine, still no movement or sound change. I never changed the torque converter.
Expert:  Mike S. replied 3 years ago.

Does the shifter at least feel like it is moving the shift lever inside the valve body? Do you have anyone there that can help you move the shifter while you look underneath to make sure it is at least moving the shift lever?

When the new tranny shifted slow from gear to gear was there also slipping? Or did the engine have to rev the rpm up beyond normal in order for it to shift?

Customer: replied 3 years ago.
I have verified that the shift lever is shifting. The engine had to rev the rpm a little before it shifted. The older tranny you had to rev the engine much higher to get it to shift.
Expert:  Mike S. replied 3 years ago.
Where did you get this transmission from? Did you get a guarantee?
Customer: replied 3 years ago.
Got it from LKQ junkyard. Yes I have a 30 day guarantee
Expert:  Mike S. replied 3 years ago.
I would tell them about it, that it is not shifting. It may have been sitting so long that some seals may have dried up and become brittle and are no longer sealing. I would really think about taking it back.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 5112
Experience: ASE Certified Master Technician
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