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thommysgarage
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Apr 23, 2016, 8:00 AM
Post #1 of 21
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700r4 drags in reverse
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I have a 700r4 from a 92 Chevy truck, installed in a 57 Studebaker, with a 350 Ram Jet. I rebuilt the trans, everything looked good to me. The trans will engage reverse, but drags badly as if it is also in forward gear. It will not pull in forward, the wheels will spin if raised off the ground. I have removed the valve body and all looks good, check balls are in the right locations, no stuck valves. I have rebuilt these before, but missed something on this one. Thanks for any advise.
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gsferraro
Veteran
Apr 23, 2016, 9:47 AM
Post #2 of 21
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Re: 700r4 drags in reverse
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Hello,
What happens in neutral, does the car creep backward? Can you put this trans in manual one? if so, what happens when in manual one? Gary
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thommysgarage
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Apr 23, 2016, 11:59 AM
Post #3 of 21
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Re: 700r4 drags in reverse
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The car does not move in neutral. Selecting low gear is the same as drive, wheels spin if lifted off the ground, but won't pull. I have not removed and checked the auxiliary valve body yet, is there a chance that is the problem?
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gsferraro
Veteran
Apr 23, 2016, 2:25 PM
Post #4 of 21
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Re: 700r4 drags in reverse
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Sounds like you may have an issue in the pump,this is also where the pressure regulator valve is located. With this trans there is nothing common to foward and reverse.
Question, did you air check the big input drum? Gary
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thommysgarage
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Apr 23, 2016, 6:10 PM
Post #5 of 21
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Re: 700r4 drags in reverse
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No I did not do that. If the issue is in the pump, what should I look for?
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gsferraro
Veteran
Apr 23, 2016, 6:47 PM
Post #6 of 21
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Re: 700r4 drags in reverse
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Hello,
From the bottom pan, make sure your filter seal is tight. In the side of the pump there should be a small filter with an o-ring, this seals line pressure. Also, check the pressure regulator valve for free movement, with the pan and filter out, you can actually remove the pressure reg valve. So, you have no foward movement, in reverse does it seem to lock-up or do you have to race the engine for the car to move? Gary
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thommysgarage
User
Apr 23, 2016, 7:23 PM
Post #7 of 21
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Re: 700r4 drags in reverse
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The filter seal was good, has been removed. The car reacts when reverse is selected, but requires some throttle to move. It is not like a loose converter, but more like the brakes are being held.
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gsferraro
Veteran
Apr 24, 2016, 6:28 AM
Post #8 of 21
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Re: 700r4 drags in reverse
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Do you by chance have a pressure gauge? sure like to see whats going on inside this unit. since it seems like it binding in reverse and no foward, you may have to get back inside this trans, i would check the pump but also look closely at the input rings and stator sealing rings, you will also have to air check the input drum, to make sure there are no cross leaks. What year is the transmission? you mentioned aux valvebody, this has the tube going into the pump?
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thommysgarage
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Apr 24, 2016, 9:11 AM
Post #9 of 21
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Re: 700r4 drags in reverse
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The trans is a 92, I did check the numbers. It has the auxiliary valve body and a tube connected to the pump. A fellow in the shop suggested it might be the low roller clutch. Does that sound plausible?
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thommysgarage
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Apr 24, 2016, 9:13 AM
Post #10 of 21
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Re: 700r4 drags in reverse
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Sorry, forgot to tell you I don't have pressure gauge. I could borrow one if needed.
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gsferraro
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Apr 24, 2016, 10:36 AM
Post #11 of 21
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Re: 700r4 drags in reverse
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If it was the low roller clutch, the car would pull off in low gear. you mentioned check balls, with aux valvebody, you should have 2 check balls in the valvebody(not including the one in the aux valvebody) Gary
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thommysgarage
User
Apr 24, 2016, 12:18 PM
Post #12 of 21
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Re: 700r4 drags in reverse
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Yes there are two check balls in the valve body.
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gsferraro
Veteran
Apr 24, 2016, 1:02 PM
Post #13 of 21
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Re: 700r4 drags in reverse
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Ok, very good, i can also only assume that you have the correct valvebody gaskets in this trans, if so, maybe before it gets pulled out, take a pressure reading to see whats going on. I would like k to know what the base line pressure is in this unit. Drive at an idle should be around 65psi. Gary
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thommysgarage
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Apr 24, 2016, 2:13 PM
Post #14 of 21
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Re: 700r4 drags in reverse
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OK, I will put the valve body back on and put a gauge on it. Do you know what size fitting it is?
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gsferraro
Veteran
Apr 24, 2016, 5:11 PM
Post #15 of 21
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Re: 700r4 drags in reverse
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should be standard 1/8 pipe. the threads on the gauge should go right in. Gary
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thommysgarage
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Apr 25, 2016, 9:17 AM
Post #16 of 21
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Re: 700r4 drags in reverse
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Checked the line pressure, it is high. It was 145 in drive and in park, pegged my 160 psi gauge in reverse. Is this definitely a pump problem, like a pressure valve stuck? I did notice that the tv lever does not contact the end of the valve when reinstalling the valve body, it has to move to probably half throttle to make contact. Does that seem right? I do have the cable adjusted for full travel at full throttle.
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gsferraro
Veteran
Apr 25, 2016, 3:18 PM
Post #17 of 21
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Re: 700r4 drags in reverse
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Hello,
Very Strange, with 145psi in drive, this thing should slam into gear. Yes pressure is way too high. With pressure that high, possible blown out seal or snapring. I would look at the pressure reg valve in the pump to see if its stuck closed, then you will most likely have to get back into this trans, but i would air check the input drum before disassembly. Being the fact that this does not move in low, the problem may be in the foward clutch, which is the middle clutch pack on the input drum. Gary
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thommysgarage
User
Apr 25, 2016, 3:32 PM
Post #18 of 21
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Re: 700r4 drags in reverse
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Thanks for your help. I will pull it out tomorrow and start checking everything. I did notice that the fluid that I drained out was very dirty to come out of a fresh trans with just a few minutes of run time on it. I think it may have been contaminated from a new trans cooler or torque converter, may be the root cause of my problem. Thanks again, Brad
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gsferraro
Veteran
Apr 25, 2016, 4:12 PM
Post #19 of 21
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Re: 700r4 drags in reverse
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When you pull that out, if you have any questions about air checking the drum or anything, while its apart let me know. I will answer as soon as i can, my shop is packed with transmission work. Gary
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thommysgarage
User
Apr 27, 2016, 5:34 AM
Post #20 of 21
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Re: 700r4 drags in reverse
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It may be a couple of weeks before I get in to it. I have lots to do as well. I will post what I find when I get back to it. Thanks for your help, Brad
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gsferraro
Veteran
Apr 27, 2016, 3:11 PM
Post #21 of 21
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Re: 700r4 drags in reverse
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Your welcome, let me know. Gary
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