[blacklabzeke]

Have a problem with my 1988 700R4. It started with a WOT 2nd to 3rd upshift and then felt like the trans went into neutral. I have no fwd or reverse and there is no noise whatsoever. When I move the shifter it feels like there is a slight engagement in all gears, but vehicle will not move. I did a pressure test.

P 80 psi
R 125
N 80
D 80
3 80
2 125
1 125

Would appreciate any info before tearing this thing apart. Thanks in advance.

 

[matt406]

i had a 700r4 that did that clutches were gone had to rebuild it. didnt know what the pressures were

 

[blacklabzeke]

The trans was rebuilt about 20K ago. Here is a list of what was installed.

Rebuilt front pump with new vanes, rings and seals.
.500 TV boost valve
modified pressure valve
all new bushings, bearings and thrusts.
Beast sun shell
replaced rear planets, sun, reaction and ring gears
replaced front planets and ring
rear sprag and plate
all new seals
all new clutches (ALTO Gray) reverse, overunning, low reverse and forward.
New (ALTO Red Eagle High Performance) 3-4 clutch pack. .040 clearance.
Kolene steels modifed .125 apply plate 8 frictions 7 steels GM backing plate.
New (ALTO black) 2-4 band
New governor
New 1-2 and 3-4 accumulator pistons.
New valve body separator plate (TRANSGO)
Transgo 700jr kit w/ TV repair valve.

 

[Crosley]

You describe a situation where the turbine hub inside the torque converter has broken out of the turbine.

The input shaft splines into the turbine hub, all power is transfered via this turbine hub. IF it breaks = no movement in any gears

Since you verified no movement in any gear selection, I suspect the converter

 

[blacklabzeke]

Once I pull the converter and transmission, how would I verify that this is the
problem?

 

[Crosley]

Once I pull the converter and transmission, how would I verify that this is the
problem?

You have a converter shop check the converter.

Or use your snap ring tool to check the turbine hub

 

[blacklabzeke]

Thanks Crosley! Do you recommend opening the trans up to look for debris?

 

[Crosley]

Thanks Crosley! Do you recommend opening the trans up to look for debris?

Turbine hub failure is typical damage is a clean break, not always as the parts are banging against each other.. I suggest dropping the pan for a debris check. If you replace the filter... break open the old filter, check for debris in the filter media.

Pulling the pump for a check is always a good idea since the trans is out any way

 

[blacklabzeke]

Do the pressure readings look OK? The readings above were at idle. When I pull the TV cable the pressure goes up, but the gauge bounces violently. Is this normal?