84 Vette Auto Trans Question

[MoeJr]

Waht would prevent an 700R4 trans to not shift out of gear at full throttle yet perform all other duties perfectly. It shifts great part throttle,the converter locks up when it is supposed to and it downshifts like it should. Light Throttle shifts happen at 13-15 mph and 27-30 mph with OD kicking in at 35. Any help is greatly appreciated. Also is the stock tach in a Vette known to be erratic? It reads good but is jumpy.

 

[Eagle85C4]

Not sure about the tranny....but the tach filter is bad. This will cause the erratic reading. it is Possible to bypass the filter, but that should be a temp fix at best. The other problem you will run into is that it is no longer manufactured. I got the schematic and built one for myself. I re-engineered the original parts and made it beefier as well as using parts that will handle the heat better as the filter is bolted to the rear of the driver side head.
Basically the capacitors in the filter go bad causing the problem. The first indication for me was that cold it would not work at all, but once the car got to operating temp it worked fine. I can build you one if you like. Parts are minimal...I will try to use the original housing ...just reattach back on the head. Cost will be parts and shipping... about 10.00...let me know...take care

 

[c4c5specialist]

Hi there,
I would suggest your checking of the fluid and filter first, as contamination in the governor will cause a symptom as this.
Now, as far as things outside the trans, I would also check for adjustment of the TV cable.
I hope this helps, c4c5

 

[MoeJr]

I am doing a fluid and filter change tomorrow and we'll see how it goes. I do have a reman governor I bought from the dealer a few days ago just in case I need it. I know my tach filter is messed up so i am gonna have that redone this winter. It reads very erratic on acceleration. I will keep u all posted.

 

[c4c5specialist]

Great to hear.
A sidebar here, split open the filter, after you let it drain a while.
Here is why, there is almost 60 in of vacuum at the mouth of a filter in an automatic transmission, and everything will be sucked up into the filter.
You will probably see some talcum like metallic power, which would be considered normal around the magnet.
Please split it open, and we can see just what is going on.
Allthebest, c4c5

 

[MoeJr]

There were some metal shavings on the magnet but nothing I would consider severe. I will try and remember tomorrow to grab the old tranny filter out of the garbage and open it up. I have also consider I could be just not used to the sound of this car at hi rpm. My tach filter is messed up so the tach jumps under hard acceleration so I am now pretty sure it isn't taching 6500 like I thought but without a functioning tach I cannot tell what the true rpm is. I will keep everyone posted.

 

[MoeJr]

c4c5 I have the filter but keep forgetting to split it open I will try again to remember tomorrow. As a side note I took the car out for a cruise and hit 76 mph in 2nd gear with no shift. Now according to the calculator on www.ondoperformance.com I punched in 26.04 inches for the 255/50ZR16 tires and 4.69 for the gear ratio(3.07 rear axle+1.62 2nd gear) and I got approx 4600 rpm at 76 mph. What is the stock shift point in an 84 Vette Auto? I need to know so I can figure out if I should let it wind any higher. The engine sounded intense at that speed in 2nd gear but I am not used to how it should sound either. All help is greatly appreciated.

Moe

 

[c4c5specialist]

HI there,
Well, technically, you should have the 2-3 upshift at 5000, from a couple of different 84s that I have in my service stable. However, for crossfire, I prefer to see the shift at 4500, due to the fact of the unique torque curve of the engine.
I would attempt the tv cable adjustment procedure first, before doing anything else.
Remember, that doing this is a little time consuming, however, very effective, if done correctly.
Remove the upper air filter cover, and the lower throttle body frame, which covers the throttle bodies.
Now, after that, you will see a couple of cables, the TV, or throttle valve cable, is the one with a large body, and a metallic push tab, on the cable, right where it goes through the bracket.
Now, push the tab, and shove the plastic piece, where the metal cable comes out, and connects to the throttle linkage, towards the firewall.
After that, release the tab, and then sit in the car.
Simply push the accelerator to the floor, and you will hear, and feel a snap/ratcheting type noise, as the cable adjusts.
Make sure your floor mat is not under the gas pedal, ok????
Please let us know if the adjustment fixes your condition.
Allthebest, c4c5