Transmissions and DrivetrainNeed help with your trans? Problems with your axle?
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First, let me start by saying hello to my fellow bowtie friends! I've rebuilt lots of engines in my time, but a transmission has never needed my attention until now.
My wife has a '84 Corvette with a THM700R4.
The transmission has some problems, let me try to fully describe them, and ask the trans gods here what may be the culprit...
If the selector is in OD, and the car is stopped, the trans will slip in 1st gear with moderate (1/3 throttle) acceleration.
If I shift to 1, it will not slip.
It's shift points are very low, but the TV cable is not misadjusted.
If the TV cable is "fooled" (adjusted) into thinking the throttle is depressed more than it really is, the shift points are indeed raised to a more "normal" level, but I can't go to WOT setting the TV cable like this for obvious reasons.
Downshifts from OD, 3, and 2 are usually only coaxed out of the tranny if you're going a relatively slow speed in top gear, and you push the accelerator pedal to a point somewhere around the left front turn signal assembly.
Running through the gears manually lets me pretty much accelerate with shift points where I want them, and no slippage in any gear (except for the rear tires for some reason ).
If I shift to any low gear and accelerate through it, at some point, usually around 4-5K RPM, it will misbehave and totally ignore what I tell it to do by shifting to the next highest gear, regardless of what lower gear I want it to be in (should I tell it to go to it's room with no supper?).
If I downshift from a higher gear, it will finally engage the lower gear when it's damn good and ready, not when I tell it that I want it to do that. Basically, it won't downshift and make the engine rev to anything higher than 4K or so, moreso from the higher gears (2,3,4) it seems.
What would you guys guess this is? Low line pressure from a bad or leaking pump? some bad clutches or sprags? sticking whoozits? bad baldersall hose clamp?
Thanks for any "remote control" troubleshooting you can give me.
I could probably rig up a line pressure guage to the thing this weekend or so if that would difinitively help us out.
Two things are needed. First and foremost is a TransGo Reprogramming Kit for a myriad of reasons, including fixing your upshift out of low problem. Next is a B&M governor recalibration kit so that you can get later shift timing which you apparently are after.
Well, wouldn't it be best to make sure the thing performs like a stock transmission before modifying it? I do plan to eventually do these types of mods, but I would like to know the thing is working properly before hand so that I don't go chasing my tail with problems. Don't get me wrong, I'm not looking for a performance shift timing, I'm looking for at least a STOCK shift timing, which I'm sure has to be something higher than the 3000 RPM WOT shift points I'm getting in auto mode right now.
Also, it would be nice for this transmission to not slip like crazy in 1st gear automatic mode, right?
Thanks!
I agree; that's probably why someone put a rebuilt transmission in it at some point in time. I doubt very seriously that the '84 slipped in 1st gear auto from the factory, either.
I will give you a few things to check, one will most likely be the problem. #1 governer for free movement and all teeth in good shape on the gear. When you check it make sure the valve moves up and down as the weights do. If that doesn't fix it take the valve body down and check for any stuck valves, especially the t.v. valve as it is notorious in earlier 700R4's for sticking. If nothing is wrong in these two places email me and tell me what you found. Good luck!!
The point Leo was trying to make (I assume) is that the Programming kit isn't about trying to make a "race tranny" out of it, but to fix the OEM blunders that eventually lead to problems like yours. I know the woes of the lackluster TV lineup in the valvebody, and I REALLY like what TransGo has done to correct this.
Almost every single OEM rebuild I did on a 700 exhibited TV related problems thanks to stock valving, regardless how meticulous I was about cleaning the valvebody and assembly techniques. Can you guess how many "side work" overhauls I have done in conjuction w/ the TransGo kit had TV problems afterwards? NONE! But thats not the only thing it corrects. There are several issues TransGo addresses, and really, its what stock SHOULD be.
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Well allrighty then! THanks for all the replies - I will check all of the above and get a TransGo kit for it as well. I didn't realize that a kit and checking the governor, etc would fix the 1st gear slipping problem - I always thought that it usually indicated a worn part when that happened. I'll let you guys know how it goes, should be able to get it taken care of in a month or so.
-Matt
I would add: that if I understand you correctly about the 700 slipping in 1st gear while the shifter is in the "OD" position and when the shifter is in the "1st" gear posisition it does not slip.....
That is a forward clutch pack, forward sprag problem or the low roller clutch is not holding..
When the shifter is moved form the "OD" to "D" or lower the over-run clutch pack comes on and holds. When the shifter is moved to the "1" position the low/reverse clutch pack comes on too.
Sounds like you have more troubles than a shift kit or recalibration kit wil cure.
I would perform the full TransGo recal kit install before changing the govenor springs and weights. The early 700's had troubles with internal shift springs getting alittle soft and causing early shifts.
if the trans was changed then mayb the incorrect govenor is in the trans.
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2001 Ford 150 SuperCrew
2000 Silverado 1500
1985 Camaro V6- .575 boost valve in the 700R4.
1962 Ford Falcon
1961 Dodge Lancer 350 chevy power
1961 Morris Minor 1000
1961 BugEye Sprite
2-1951 Crosley wagons
1948 Crosley wagon
1947 Crosley Sedan
1947 Crosley Pick-up
1948 Simca
[This message has been edited by Crosley4 (edited December 08, 2001).]
The reason that the transmission does not slip when you are holding in manual low is the low/reverse boost valve is activated. This raises line pressure a certain amount (depending what size the int/rev boost valve is), by doing this it is keeping it from slipping. If this unit was exactly as it came from the factory (NEW), then you would not have these problems. By installing the Trans-Go Shift kit or the Performance Shift kit it will address the inherent problems of the 700R4. You will still to have the unit built correctly (all the updates) for the Shift kit to do its job. If I can be of help please call or email me.
Glad To Help!!!
The TransGo kit solved all the issues I'm having, except for low automatic shifts. I guess it's probably in the governor, but I can live with it - it's fine as long as I'm not trying to run any 1/4 mile races; for around-town driving it's working great in that department.
No more slipping in 1st, nice crisp shifts, woohoo!
).
