closer

My car is a stock 305 TPI, and the 700r4 seems to shift fine around town with out being harsh or sloppy.
But once I get out to the highway.. this car has never shifter into overdrive until it gets just above that blue line at 55mph. Once it goes in it does like it should. I never get the car into much of an uphill load to see if it kicks back down when it goes under 55.
I just got it back on the road after sitting in the garage for awhile. I kind of remember it not ever kicking down out of OD when going to pass unless I'm doing under 50mph.
But I do remember... and it still does it. If I let off the gas coming into a small town. Once it gets under that 55MPH there's no compression engine braking. It just acts like It's in neutral. The revs drop to idle.
If I rev it up to match the speed the trans will pull up in speed... just acts like neutral slowing down.
When I come to a complete stop it operates fully like a normal automatic trans and starts of in 1st. If I pull the shifter down out of OD manually in this "free coasting" the gear grabs right off and slow the car down.
I remember going through the TV cable adjust procedure when I last drove the car. Does this sound more like a TV cable, VSS sensor, or a weak OD section in the trans to you guys?

vorteciroc

-The the Fluid Level.
-Take Line-Pressure readings for all Gear-Ranges at Idle and at 1,200 - 1,500 RPM.
-Take Line-Pressure reading when abnormal behavior occurs.

List any modifications, and type of Torque-Converter.
List how TV System is set, and how TCC is configured.

The Unit is definitely a 1986?

closer

I bought the car as it is. All stock car with 123k miles. Stock converter, stock lock-up operation controlled by the ECM.
TV cable was set per the write up I had found on the forum for a "stock" car.
Fluid level is correct, and barely has any discoloration (I flushed and changed when I re-assembled the car 12 years ago).

How can I check the line pressures? I've never done that before. I'm sure there's a tool set I can buy to use. Harbor freight maybe?

Now that I've gotten the chance to drive it a few more days. It's not as bad. Still, under light throttle take off it won't go into OD until it reaches exactly 55mph on the speedometer. I can get it to shift at 50mph if I jab the throttle and let off. But it still acts like it drops to neutral once coasting roughly about 45mph on down to a stop. The rest of the shifts are solid and have no issues around town or on the highway, I also tested and it does kick down for passing gears at 55mph with no issues.

I'm probably just beating a dead horse. It all works as it should except the issue while coasting to speeds under 45mph.

RBob

iTrader: (1)

The neutral feeling in OD with no throttle is normal. The over-run clutches are not engaged once the trans shifts into OD. They are engaged in 1st, 2nd, and 3rd. Which is why 3rd creates engine braking.

As for the upshift into OD at 55 MPH, that seems a little high. Although someone may have been in the trans and made some changes.

RBob.

vorteciroc

Line-Pressure is measured with a 0 - 300 Psi Hydraulic Pressure Gauge (sold in the Automotive World as a Transmission Line-Pressure Gauge).
There is an 1/8" Plug installed on the Driver-Side of the Transmission Case, to install the Gauge.
Shown below:


The timing for the 3rd to 4th Shift is going to be dependent upon the 3-4 Shift Valve-Train, and the Throttle-Valve Plunger and Sleeve Set.

You would have to go into the Valve-Body, so that I can see which versions of these Parts are being used in your Transmission.

skinny z

I had the same thing happen to me when the forward sprag assembly failed on a newly rebuilt 700R4.

vorteciroc

Generally if that Sprag fails...
The Transmission will only move the Vehicle with the Gear-Selector in the Manual 1st-Gear, and Manual 2nd-Gear positions.

skinny z

In my case, I was handed the offending part by my builder.
It was mangled.
That said, I'll have to get back to my ATSG manual to confirm that part description.
I'll reference my thread from 15 years ago.
https://www.thirdgen.org/forums/tran...381-700r4.html