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Old 05-09-2012, 09:35 PM
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700r4 with no overdrive when hot

700r4 rebuilt with Monster Kit, bigger servos and bands, superior shift kit behind a 400sbc street rod (2900lbs) about 400 HP. 1100 miles on car and tranny. Shifts good and goes into overdrive and converter locks up and engine drops 300 rpm just as it should. Pressure gauge shows 160 to 170 lbs when outside temp is 60 degrees or colder. When outside temp is above this and about 20 mile trip, pressure drops too 130 to 145lbs and if I have too slow down it will kick out of overdrive and it won't go back into overdrive. Have had the pan off and made sure TV cable was fully depressed at WOT. Pan was taken off at 750 miles with no metal or crud in pan. Oil was clean and smelled good (not burnt). Tranny shifts hard and fast in all gears even when it won't shift into overdrive. Shifts from 1st to 2nd at 3000rpm, 2nd to 3rd at 3000rpm even when hot. Have new steel cooler lines running to radiator and then thru external cooler. Can hold hand on return line and its not extremely hot. Only running Carquest Dex/Merc trans oil. Would a different oil be used? Anyone have a suggestion?

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Old 05-10-2012, 01:28 AM
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What are your pressures at minimum TV and maximum TV?

Keith
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Old 05-10-2012, 10:41 AM
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archcar

I have 150 to 175 park tv connected,
225 reverse tv connected
175 o/d tv connected
175 3rd tv con
200 2nd tv con
200 1st tv con

80 park tv dis/con
125 rev tv dis/con
80 o/d tv dis con
80 3rd tv dis/con
180 2nd tv dis/con
180 1st tv dis/con

190 park fast idle full tv
200 rev fast idle full tv
190 neutral full tv
175 o/d fast idle full tv
180 3rd full tv
190 2nd full tv
190 1st full tv
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Old 05-10-2012, 12:38 PM
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How is your trans wired to engage the OD? Is it a pressure switch on the valve body that is hooked into 4th oil? If so, I would wire in a temp manual lockup switch, and see if you can lock it up in third or fourth manually. Your probably already wired for it, just need to hook it into the trans plug. It will be a separate position in the plug. You will have to verify that though.

Keith
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Old 05-10-2012, 02:46 PM
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700r4

Wired thru 4th pressure switch and also extra switch on dash too lock it up in 2nd and 3rd also. I un hooked it and had 2300rpm in o/d at 75mph. Hooked it back up and dropped 300 rpm. When it gets hot outside it just won't shift into o/d. TCC lockup wiring does not go thru temp switch or thru a brake switch. Have never tried too see if the engine drops any rpm in 2nd or 3rd when the TCC locks in. It just won't shift into 4th when the temp gets hot outside and I have driven over 10 or 15 miles. It will shift into 4th when the tranny is cool and hold in until I have to slow down or stop. It then shifts thru all the gears but will not shift into 4th.

Last edited by Archcar; 05-10-2012 at 03:12 PM.
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Old 05-10-2012, 10:48 PM
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I just want to make sure we are talking the same thing. The 700 is a 4 speed with OD. Will it shift into 4th gear when hot? 4th gear isn't overdrive. So, if it won't shift into 4th gear it won't shift into OD. When it does this, if you manually engage lock up in 3rd gear, with the switch, will it lock up? If it does, we can rule out the convertor. In fourth, the 3/4 clutch pack is engaged just like third gear. Also, the 2/4 band will also be engaged. I would put the pressure gauge on the 4th gear oil passage on the right side of the transmission, and see if you have 4th gear pressure.

Keith
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Old 05-11-2012, 06:11 AM
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Quote:
Originally Posted by blwn31
I just want to make sure we are talking the same thing. The 700 is a 4 speed with OD. Will it shift into 4th gear when hot? 4th gear isn't overdrive. So, if it won't shift into 4th gear it won't shift into OD. When it does this, if you manually engage lock up in 3rd gear, with the switch, will it lock up? If it does, we can rule out the convertor. In fourth, the 3/4 clutch pack is engaged just like third gear. Also, the 2/4 band will also be engaged. I would put the pressure gauge on the 4th gear oil passage on the right side of the transmission, and see if you have 4th gear pressure.

Keith

Your post confuses me a bit.

In a 700r4 trans , 4th gear is Over drive. 4th gear is a .70 gear ratio.

I believe you may confuse the converter clutch locking up as Over drive. Converter clutch lock up is not Over drive in the 700 trans


The OP trans case may not have a 4th gear pressure port on the passenger side depending on the year of the case. The OP needs to look at the case for the pressure ports.


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Old 05-11-2012, 09:17 AM
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700r4 no o/d

Sorry to confuse you. Its only 50 deg here this morning so couldn't test. It shifts thru all 4 gears and the convertor locks up when I switch it on (I drop 300 rpm). At this speed I carry 2000 rpm/75 miles/hr. On a hot day it will not shift into 4th. I go 75 mph at 3300 rpm. Have no effect if I switch TCC on or off. It is a new converter. I suspect that I got valve body parts installed wrong. Although I only took out 1 valve at a time and replaced them with new springs from shift kit. Under hard acceleration it shifts hard and fast third gear and seems too slip a little when it goes into 4th. It is not a clean hard shift into 4th (on a cool day or when tranny is cool). On hot day it won't shift at all into 4th. I ran up to 95mph and 4000 rpm, up and down hill letting off the gas it still would not shift into 4th or o/d is what I call it. TCC switch has no effect that I can tell.
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Old 05-11-2012, 11:15 AM
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Thanks Crosley, I'm not trying to confuse anyone just got my terms slightly off. And you are correct, 4th is called overdrive and lock up is just that...

Archcar, This is out of one of my manuals. This is the description D-4Overdrive:
As both vehicle speed and and gov press increase, the force of gov oil acting on the 3-4 shift valve overcomes the force of the 3-4 T.V. spring and M.T.V. up oil. This opens the 3-4 shift valve sending Drive (D4) into the fourth signal passage. Fourth signal oil will overcome the 4-3 sequence valve spring and open the 3-4 relay and the 4-3 sequence valves, allowing second oil to enter the servo feed passage.

I wonder if you have an internal leak once the transmission is hot? Seems per you description, it would indicate a lack of pressure or something in the governor. Since nothing happens for fourth gear, and just stays in 3rd.

Also, if you have the fourth oil pressure tap on the right side of the case, ATSG Manual says:
As a diagnostic aid, you can check the oil pressure differential between line pressure and the 2nd, 3rd, and 4th clutch pressure while driving the vehicle. If the pressure differential between line pressure and any of the clutch circuits is more than 10 psi, there is a possible leak in that clutch oil circuit.

Hope some of this info helps.

Keith
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Old 05-11-2012, 12:00 PM
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700r4 no o/d

It helps alot. Thanks for the reply and your help. Sure like your car. I will work on possiable internal leak and tell you the results, thanks again, Archie
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Old 05-14-2012, 07:38 AM
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check the servo for 4th gear. maybe the teflon ring was cut or, the wrong one installed.
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