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Old 12-23-2004, 06:06 AM
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TH700R4 Slipping 4th only.

Hi,
Ive got a recently rebuilt 700r4 behind a sbc350. Its around 1985-6 year and had the following parts

fitted: (By my rebuilder)

35960 super servo 1-2
sx77767k sonnax 4th gear servo
35995pbk kevlar power band
hp35003r-k master kit with red eagle frictions
35601 bushing kit
35393 lockup solenoid
35669 bearing kit
35670 washer kit
35823b sun gear shell hd
35764A-K 13 vane pump kit
35361 moulded forward clutch piston
tvb101 valve body plate seat repair
35890 governor (petrol)
35920 filter
35880 sprag 26 element
Transgo shiftkit

The drum was put in a lathe to ensure it was flat, and had the band manually applied during first

startup. Car drives well, shifts well, holds all gears (esp.2nd) and lockup works. Car is a 4x4

truck - 1800 kilos,35" tyres.

However, it has slight slipping in 4th gear. it only slips by a few hundred RPM and then settles down again.

My rebuilder has finally reproduced the problem, but is not sure exactly what to change. He says

that the band must be good becuase it holds perfectly in 2nd. So it must be a valving problem on the

4th gear part?? (Makes no difference if TCC is applied)

I also mentioned my intention to fit twin turbo's to this car, aiming for initial 450bhp, probably

500ft/llb. He said I should fit a manual valve body to "make it last" - becuase it applies much more

pressure to all the plates and short make it live longer - is this true or is he looking for an easy

way out of the 4th gear slipping problem?

Ive done some searching around, TCi seem to sell manual bodys - with "engine breaking" - aimed

presumably at the 4x4 application such as mine. What are manual bodys like, do they crash when changing gears or is it cushened?

ive searched all the manual valve body and 700r4 threads on here too.

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Old 12-23-2004, 11:42 AM
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did you expand the 3/4 clutch pack? I did not see that on your list?
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Old 12-23-2004, 12:04 PM
67 Nova 400sbc.4L60
 
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700 R4 4x4 slipping in fourth

First I would road test the vehicle in third at different throttle positions and try to verify if it slips in third at any time. This would mean the 3/4 clutch is the problem, secondly if the problem is only in fourth then the band is applied again with a different section of the servo than the second servo . A two stage servo is used ,so then I would remove the servo and verify ****embly. Then if the third gear is OK and the TV cable is adjusted properly then I would go through the valve body. One note! If the original intake and/or carb has been changed then the geometry of the throttle valve cable hook up should be verified.
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Old 12-23-2004, 12:16 PM
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Re: 700 R4 4x4 slipping in fourth

Quote:
[i] If the original intake and/or carb has been changed then the geometry of the throttle valve cable hook up should be verified. [/B]
GOOD POINT! TCI sells two seperate tv cable brackets one for quadrajet and the other for holley carbs, they are diferent and should not be swaped!
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Old 12-24-2004, 04:57 AM
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Hi Guys,
Thanks for the replies so far.

Yes, I believe the 3/4 pack had the extra plate fitted.

It only slips in 4th - 3rd is fine.

I followed the varios sources of setting up the geometry and when I compared against an old TBI I had laying around it was the same. The only thing I couln't acheive was having the bracket at the same height as the throttle shaft (roughly) becuase my fuel rails get in the way. So its a bit lower (about 1 inch).

My transmission guy suspects a valve body problem also.

The pressure at the test port at around 2500 rpm, 4th - when the problem occurs is around 130psi (I think - quite a while ago now)
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Old 01-06-2005, 10:56 AM
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My transmission guy has removed the valve body and checked spring lenths etc. says he cant find anything wrong and therefore the valvebody must be worn, causing a low pressure in 4th. I'm giving up with him and will attempt to sort it out myself.

So do i buy a manual VB or auto VB - My trans guy says I should fit a manual VB due my itention to put a considerable amount of power through it.

So...

Has anyone got any experience of the tci manual valve body? - What are the shifts like? does it still use the TV or Governor to adjust the feel of the shift depending on how youre driving it, or just it just crash up and down the gears hard, regardless of how you want or need it to?



Thanks,
Eliot.
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Old 01-06-2005, 09:38 PM
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A full manual valve body does not hold the power any better than a properly set up automatic shifting valve body.

It also involves the proper parts internally ( frictions , steels, boost valve ) to hold the power.

You need a quality tranny guy to diagnose the problem with the 700. It is difficult to do that over the internet sometimes.

lets us know if you need additional information.
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Old 01-06-2005, 11:58 PM
67 Nova 400sbc.4L60
 
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700R4 no Fourth Gear

Another thing I forgot to mention earlier is you have an early case 1983-1988 They have three 1/4" pipe tap plugs around the servo you can check pressures while you are driving to diagnose your slipping problem. One is for second gear oil, the next is for third and finaly the last is for fourth gear. the one on the oposite side is for Mainline if you have a gage on mainline and one on fourth gear the pressures should be the same , if the fourth circuit is leaking then the fourth gear pressure will be lower than the mainline pressure. My wife and I once drove thirty miles with three gages coming into the passenger window to determine why a Blaser kept dropping out of fourth gear and it turned out to be a fuel filter.
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Old 01-07-2005, 03:07 AM
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Thanks for the response.
I asked my tranny builder if i could use those ports to diagnose the problem and he said no!. I dont think good exerienced (American) tranny builders exist in the UK.
The box has all the uprated red eagle frictions and super servo etc.

Here's a photo of my actual tranny (Before it was rebuilt, hence std servo):
http://www.mez.co.uk/dcam/DSCF0232.JPG

which ports are which? - I suppose Id better get the service manual for this box if i'm to try and fix this myself.

Is anyone able to answer my question about the feel of the shifts with a manual body on it? - I'm putting turbos on the car, I'm thinking a manual VB may suit them better?

Thanks,
Eliot.

Last edited by eliotmansfield; 01-07-2005 at 03:19 AM.
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Old 01-07-2005, 07:59 AM
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Cool

Full Manual valve bodies shift very firm.

If you are installing turbos on the vehicle , chances are you will break the input shaft and/or the aluminum drum in a short time

Full Manual valve bodies shift very firm.

If you are installing turbos on the vehicle , chances are you will break the input shaft and/or the aluminum drum in a short time
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Old 01-10-2005, 12:06 PM
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Quote:
Originally posted by eliotmansfield


So do i buy a manual VB or auto VB - My trans guy says I should fit a manual VB due my itention to put a considerable amount of power through it.




Thanks,
Eliot.
If you intend to have more than 500 hp in your engine? save yourself allot of money and look at some other tranny! the 700 cannot handle it !was not designed for this! they can be custom built for it but you wil not find a converter to withstand that much torque(over 500) even custom converters cannot handle it! although some one may jump in and say they know of some one or some outfit that clams they can build a converter ? it will be very expensive and after you by it you own it! since you will not get a waranty for a racing torque converter
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Old 01-10-2005, 01:03 PM
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Quote:
Originally posted by ronb
... but you wil not find a converter to withstand that much torque(over 500) even custom converters cannot handle it! although some one may jump in and say they know of some one or some outfit that clams they can build a converter ? it will be very expensive and after you by it you own it! since you will not get a waranty for a racing torque converter
I guess I'll have to jump in

I bought a 9 1/2" Vigilante converter from Precision Industries for my 700R4. At the time I bought it (about 6 years ago), they were advertising a three year warranty no matter what you used it for. Now, it is 24 months and they state under "normal use". While they do not exclude racing (see warranty here), I am not implying that they will cover it under any heavy duty usage, including but not limited to racing or off-roading. At the time I bought mine, they considered putting it behind a Pro-Street BB "normal use".

Now, I am not saying this is the best thing since sliced bread, but I am happy with mine, even though it is only behind about 475 HP. But as ronb said, they are expensive, about $725 now. Here is one source I found using Google (scroll down the page)

If you plan on 500 HP or more, I would consider a 4L80E transmission instead, that is, if you want OD.

Good luck, Ed www.edgesz28.com
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Old 01-10-2005, 01:33 PM
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Re: 700 R4 4x4 slipping in fourth

Quote:
Originally posted by paul poirier
First I would road test the vehicle in third at different throttle positions and try to verify if it slips in third at any time. This would mean the 3/4 clutch is the problem, secondly if the problem is only in fourth then the band is applied again with a different section of the servo than the second servo . A two stage servo is used ,so then I would remove the servo and verify ****embly. Then if the third gear is OK and the TV cable is adjusted properly then I would go through the valve body. One note! If the original intake and/or carb has been changed then the geometry of the throttle valve cable hook up should be verified.
i would have to agree here, unless a sticky valve in valve body or maybe a problem in the drum, which it doesnt sound like.
the servo is easy to remove to check and see if a seal got cut or something... ive seen it before, so it a good possibilty.as far as if thats not it, id go with checking psi. if thats all good., then id go valve body... i usually try to go with what makes most sence 1st, then try whatever is gonna make the least amount of mess... lol
gl
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Old 01-10-2005, 04:09 PM
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I picked up the car this weekend and drove it back home about 60 miles.
I pretty much managed to drive around the slippage by just accelerating gently in 4th.

The line pressure at around 2000 rpm / 70 mph in 4th locked up was around 120 psi, giving it WOT it would go up to about 140psi but then it would change down to 3rd. All my line pressures always meet the MINIMUM values, but i never see them above those values. When you see MAX pressure does that mean max pressure at high rpm and throttle angle ?

The thing I did notice on the way back, that when it was locked up in 3rd with wide throttle I think it was slipping very slightly also, if you unlocked it (in 3rd) it didn't appear to slip. 4th gear slips regardless of lockup.

I accept what you guys are saying about the power handling of this box, Iím aiming for around 8psi boost into a 350, so ~450 BHP , driven sympathetically (No drag racing/ heavy starts) - I know it's borderline - I'm hoping it will last a little bit!. Its got all the red eagle clutches etc, just hope the input shaft and drum hold up.

Changing the box again at this stage would involve alot work and custom fabrication, as its beeing mated to a Range Rover transfer box.

I did start looking at the 4l80e last night, it's certainly strong! - but fitting it to mine would require allot of cutting and fab. Plus i need a controller and they appear to be v. expensive. I do know of someone whos doing a controller based around the Megasquirt ECU that I use, so maybe in the future I could consider that avenue.

See http://www.mez.co.uk/Chevy700r4.html for an idea of the issues of fitting this box to a range rover.

Ive got a manual VB on order right now, so I'll see if that makes any difference.

Thanks,
Eliot.
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Old 01-10-2005, 05:29 PM
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in my personal experience, i havent seen a single input shaft broken on a 700r4., 27 or 30 spline. from what uve just added to on the post, its starting to soundlike 1 of 2 things, 1st off, r u sure that its completely full of fluid? they will hold over 11 qts of fluild from dry (including cooler). sounds like it could be just a bit low. otherwise, its starting to sound internal. other than that, if pressures r low on all ranges, maybe the pr valve got some trash in it by chance and its stuck. still sounds like fun.. i like these types of cases to try and figure out., gl
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