Ouch! Speedo failed, now will not shift out of first

[trentc]

Well it did for a while then I have to stop and put trans into park and it would start shifting again, then had to stop engine.

Now nothing.

What do I start with this? Is is mechanical or electrical ?

Thanks

[JohnC]

If it's a 4L80E, good chance the ignition switch is bad. If it's a 700R4 shifting is mechanical....

[trentc]

Since I have an '88 and the 4L80E was not around until the 90s, I would have to say it is a 700R4.

So is there a target area I should be looking at?

Suspect failure areas?

Thanks

[DmaxMaverick]

Check the area of the of the governor (rear of the tranny, large round plug on the side). The speedo drive is right behind it in the tailshaft housing, if it is 2 wheel drive, but at the rear of the transfer case if 4x4. Something in the governor could have grenaded, preventing the shifting, and screwing up the speedo drive. If it's a 4x4, you may have more than one issue (coincidence, but I doubt it). The 88 Burb should have a mechanical speedo drive (cable). It is possible the plastic speedo drive gear (make a note of it's color) came apart, and has plugged a hydraulic passage.

[trentc]

Thanks! I will crawl under there tomorrow and let you all know.

[trentc]

I finally got under there to look at it.

I guess the problem is much worse.

The plastic speedo drive is fine.

What next? Governor gear?

[trentc]

I took this out a while ago. I guess this would be the reason why the transmission is not shifting/speedo not functioning?

http://i317.photobucket.com/albums/mm361/tcreek/IMGA1044.jpg

[DmaxMaverick]

I took this out a while ago. I guess this would be the reason why the transmission is not shifting/speedo not functioning?



Just a guess, but, um, yeah....

[trentc]

Okay, I am just trying to be sure. I just don't have the money at this point to put new parts on the vehicle that do not fix the problem, as much as I would like to.

I was comparing it to a picture I saw where the gear is straight, and not curved as mine is.

http://images.streetrodderweb.com/images/0801sr_13_s+gm_700_r4_overdrive_automatic_transmis sion+.jpg

Thanks!

[trentc]

Any ideas on where to get this part?

Not at the local parts store and I think dealerships have long stopped carrying it.

[DmaxMaverick]

Any good tranny shop should have it, or be able to get it. Just show them your old part, and they should know what it is right off.

www.rockauto.com is showing the governor drive gear, part #8663995, for about $11.

[john8662]

cool picture, first time I've read/heard of this one, I figured it was a fluid level issue.

You also confirmed you have a TH700 transmission too.

Ditto on the trans shop having the parts, probably on hand.

[trentc]

I found one of those "mom & pop" shops down the road from me that had it for only $3.

Took me only 15 minutes to change out and install.

Speedometer still not functioning and I now get far as second gear.
I wonder if it is a fluid flow problem.

Though it now goes into second, it only does it when the RPMs go a bit high.

Any more ideas beside a rebuild? That local shop said they would do a rebuild for $400, but I cannot get it done for over a month.

[JohnC]

OK, I'm going completely out on a limb here.

Suppose the speedometer (or cable) failed and caused the gear to fail? Suppose also the bits from the gear caused the trans to fail?

I can't see how a problem with the speedomater would otherwise affect shifting.

I'd drop the pan...

[DmaxMaverick]

If the speedo isn't working, you still have a mechanical failure at some point. Verify the cable still turns and is connected to the speedo. Verify the speedo drive gear is intact and turns with tranny output speed. Is this a 2wd or 4x4? If 4x4, the speedo drive isn't in the tranny, it's in the transfer case. If 2wd, it is possible (and sounding likely) the speedo drive has in some way failed, allowing pieces of the gear, shaft, key, worm, etc. may have entered into the hydraulic system, or is interfering with something mechanical (perhaps the selector detent/valve). The 700R4 will shift out of 1st gear, if 1st gear is selected (intentionally or not) and governed speed is exceeded (near redline).

Or....you are experiencing a series of unlikely coincidence. It happens.....

[trentc]

Okay I did some more testing. It is 2WD BTW.

The cable turns, but I need a helper to see if the needle moves inside.

After sitting for a few hours, I took it on a test drive. When I took off, the transmission was not grabbing very well at all (not slipping). Which made me think pressure problem. I guess it is that.

After a while it started grabbing again just fine. To see what would happen I took it on a highway service road and got up in speed. Turns out it does shift in all gears. The problem is that the RPM requirements to get into the next gear is quite high. So I took it on the highway to try to get fourth out of it. The speed requirement in third to get high RPM was too much speed. I was at least 85 and still not enough RPM to go into fourth. So maybe plastic parts from it did get into the system.

All that does not explain why the speedo failed at the same time the shifting went out also.

There is no tach in it so I am guessing by the sound it is shifting at redline.

Thanks!

[HillBilly2]

Sounds like the governor you found may have come from a gasser. That would make it almost redline before shifting. The diesel's use a different one with different springs and weights to make it shift at the proper rpm.

[trentc]

I did not change out governor, only the plastic gear.

[CedarGrove]

Nobody has mentioned the tv cable yet. My 84 was doing something like this earler this year. I adjusted the tv cable and got the shifts to act better, but then the transmission totally grenaded 3 days later.

I'm not much help here, but I was hoping someone would chime in about the throttle valve cable. Any takers?

Lewis

[trentc]

Nobody has mentioned the tv cable yet. My 84 was doing something like this earler this year. I adjusted the tv cable and got the shifts to act better, but then the transmission totally grenaded 3 days later.

I'm not much help here, but I was hoping someone would chime in about the throttle valve cable. Any takers?

Lewis

I called the shop I bought the screw gear from.
He said that there are only 3 governors for that transmission. 1 for corvette, 1 for V6, and 1 for the rest of them.

He mentioned I should try to adjust the CV.
Before I changed the screw gear, the transmission was shifting, but not like it should have been.
Guess I will take a look at the CV tomorrow. It has taken a while to understand how to adjust it since most guides already assume you know your way around a transmission.