Thread: Trans question 700R4

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Hello there,
My transmission doesnt work properly. Now I've got my engine running nicely my trans doesn't work all too well. It seems to have a generous amount of slip, although it's a new rebuild and the pressures are OK.
It's a 700R4 behind a 350 SBC in a Chevy G20.
Here are my questions:
1. How do I drain all the fluid? Not just that in the pan?
2. How do I notice whether my TCC is locking up?
3. How would uncorrect thrust washers influence the driving quality of my trans?
Hope someone can answer these for me, I feel like I'm ready for the next pulling of the transmission in the near future (I'm getting quite an expert on that )
Thanks a lot,
Max

Try this. Set the T.V cable correctly. The TV cable should be hooked to the carb on the lower half of the throttle linkage. In this way the cable is pulled forward under acceleration. This hook up knob on the linkage (the plate on the shaft of the butterflies) should be at the 4 o’clock position at idle and 8 o’clock at full throttle. The T.V. cable should be fully extended just prior to full throttle. The knob hook-up should be 1.125 inches outbound from the axis of the butterfly shaft at the 4:00 o’clock position when closed..

This part is absolutely crucial to the proper working of the 700 and I believe the misadjustment of this cable is the single most often reason for failure of the 700 tranny. I can not stress this step enough. If the cable is not set correctly, the shifts will be sluggish and early in rpm. This will cause the tranny to self destruct in a single outing.

Thanks Typhoon, but my TV-cable is set correctly, I know how crucial that is. Also my pressures are OK. That's what makes me wonder if it might be that I installed the wrong washers and maybe the clutch packs are simply that little bit too far apart... My converter is brand new and the trans fluid seems OK, too... I somehow think my tranny is alive and wants to test me
I'll put in new fluid with an anti-slip additive and try again, lets see if that helps. I'll return to this trhead at the end of the week for news.

Originally Posted by MadMax

It seems to have a generous amount of slip, although it's a new rebuild and the pressures are OK.

I am wondering if the slip you are experiencing is the stall on the torque converter. Do you happen to know what stall it is? If one has a high stall converter, say 3000, and if you have a sift kit installed, it will seem to be a sloppy shift.

Originally Posted by MadMax

1. How do I drain all the fluid? Not just that in the pan?

You will want to drop the pan and the oil, install a new filter, reinstall the pan, disconnect the tranny cooler lines, hang one line in a new pail of tranny fluid and the other to catch the fluid coming out of the converter. Start up the engine and allow a dozen of quarts to cycle throgh the tranny and your done.

Originally Posted by MadMax

2. How do I notice whether my TCC is locking up?

Ok, this is easy. Drive down the road at 2500 rpm in third gear postition or in OD. The tranny will have to be warm. Once the converter locksup, it will operate as if it is a standard transmission, no gain in rpm when you step on the gas slightly. As the vehicle speed increases, so will the rpm of the engine.

Originally Posted by MadMax

3. How would uncorrect thrust washers influence the driving quality of my trans?

Exactly which washers are we talking about? If your clutch packs are too loose, that would do it. I think you want about .020 (twenty thousands of an inch.)

Hi Typhoon, thanks for the input, i read somewhere how to get all the fluid out of a trans, but I forgot how to and couldn't find the source anymore. I'll try that. As for the lockup, my TC only locks up in OD, and it does seem to do so, but as soon as I get onto the gas just a little harder it slips again and doesn't accelerate as fast as I think it should do... I know a TC has some slip, but maybe I'm also wishing for too much in a 5000 pound car My TC has a very low stall speed, around 1500.
By thrust washers I mean the washers inside the trans which go between things like input drum and 2-4 band drum etc. The ones where you get a little bag in any rebuild kit so you can make sure to get the correct ones. Now I rebuilt my trans with the clutches all well soaked in oil, actually dripping when I put them into their packs. So that would mean there were many oil films between the clutches when I installed the washers and set the clearance right. So when the trans started up first time it would probably press a lot of the fluid from between the clutches and thus make the clearance bigger (and possibly the first compression of a new clutch might squeeze it just a litttle bit, too). I just hope that's not true, I don't fancy taking out a $ 2000 trans and spend a whole weekend to change a $ 1 washer
It's my first trans rebuild and I have been using it for about 4k miles, the condition doesn't seem to get better or worse, and the fluid is still unburnt, so I don't think I'm breaking it, Maybe I should just pull it out and check clearances anyway... I'm not fussing about my shifts, they're definitely nice and firm, I can get them to really jerk the vehicle by shortening the TV cable a bit (just for tests ) But just after the shifts it feels sloppy again. So when I accelerate it jerks at shifts and then only accelerates slowly, but with high engine RPM. It's definitely not a weak engine
A friend of mine has a pickup (only a bit lighter than my van) with a 400hp SBC in it, also with a 700 trans and it pulls quite a bit better. Just makes me wonder...

Originally Posted by MadMax

As for the lockup, my TC only locks up in OD, and it does seem to do so, but as soon as I get onto the gas just a little harder it slips again and doesn't accelerate as fast as I think it should do... I know a TC has some slip, but maybe I'm also wishing for too much in a 5000 pound car My TC has a very low stall speed, around 1500....

u know what Max, it sounds more and more like a loose faulty converter.

Originally Posted by MadMax

and possibly the first compression of a new clutch might squeeze it just a little bit, too). I just hope that's not true, I don't fancy taking out a $ 2000 trans and spend a whole weekend to change a $ 1 washer....

I can't see that being the case.

Originally Posted by MadMax

Maybe I should just pull it out and check clearances anyway...

If you checked your clearances even with the frictions dripping in oil, they will be fine.

Originally Posted by MadMax

my shifts, they're definitely nice and firm, I can get them to really jerk the vehicle by shortening the TV cable a bit (just for tests ) But just after the shifts it feels sloppy again. ...

*cough* torque converter.

Originally Posted by MadMax

So when I accelerate it jerks at shifts and then only accelerates slowly, but with high engine RPM. It's definitely not a weak engine ...

**cough** tc

Originally Posted by MadMax

A friend of mine has a pickup (only a bit lighter than my van) with a 400hp SBC in it, also with a 700 trans and it pulls quite a bit better. Just makes me wonder...

***cough***

If the clutches or band were slipping, they get progessively worse as the days go by, not weeks or months. It happens quickly and the oil would be burnt. Do you happen to have another TC laying around which you could try? That would be a whole lot less work.

Please define "after it shifts it feels sloppy again."

By "after shifts it feels sloppy again" I mean the following:
When it shifts it really kicks into the new gear, especially at high RPM shifts. But shortly after the shift the firm feel is gone. When I really step on the gas the engine revs up and the car gets pulled forward quite hard, but then the acceleration goes away steadily even if the engine is reved higher.
I do have a shift kit for HD-use and a 13 vane pump installed, can that be a problem? I read somewhere that 13 vane pumps don't produce the volume a 10 vane pump produces, but can create higher and more constant pressures, so I threw it in. So maybe the pressure is high enough for the shift, but then the volume of oil isn't enough to fill the clutch applicating pistons... But I shouldn't think that would be a problem... Maybe I should pull out the shift kit, which does feature bigger holes in some of the oil feeds, but all that would cause slip in the clutches...

@ Typhoon: I had this problem with my old TC, and I thought it might be a TC-fault, so I bought a brand new one and it's exactly the same. I.e. it's not the TC, I don't think I would get a TC brand new that just happens to have the same fault my old one had. Anyway, how can a TC break? The clutch can get worn, but all other parts are surely not prone to deterioration, except for the stator sprag and bearings maybe, but they last quite a time...

This is where my problem is: I built the trans myself and it works, but not to my full satisfaction. And I can't find the fault. I'm really stumped by this one, especially because I don't seem to be breaking anything, everythings new, just the performance is lacking...