TH-700R4 Thoughts and advice?

[swissarmychainsaw]

I have a 1984 Chevy Silverado, 305 Th-700R4 shortbed 2wd.


I have owned this truck for just under four years and have been struggling with (and paying for) this transmission more than I would like. The truck is really nice, but I need the trans to work better.
(I'll go in to what "not working right" means).

Special Notes:
Accelerator pedal feel is very stiff meaning you have to really press down hard to "give it gas". I'm now wondering if that is related to the Throttle Valve Cable.

Mostly this truck sits around, but I do take it road trips, camping or dirt biking.
So it's either sitting, or on the highway.

Transmission has leaked for years, and with the last trip to the shop I think we finally have it stopped.

Transmission Shifting:

Normal:
Typically shifts early. Driving up a steep hill, it will shift into higher gear, so I have to nearly floor it to just keep it in a lower gear to climb the hill.
It has behaved this way for the 4 years I have owned the truck. (Now I think that this indicates throttle valve issues, since this controls shift points).

Not Normal:
On a road trip to death valley (aka after 6 hours of driving); the transmission started shifting really late. First to second shift would shift only at
high RPMs, and so on. I was able to get it home, as cruising on the freeway was ok, but this was a sudden change and concerned me a lot.
(had transmission serviced, pan gasket replaced, which was leaking) I don't remember what all he did, but I remember that he replaced a broken
plastic gear, which was either orange or green. this was three years ago.
As I recall this helped things for a while, but the trans still leaked, but I believe that the shifting was back to "Normal".
(I must say I took this to a place that specializes in Differentials, they are not a trans specific shop. They got good review on yelp and I like and feel like
I can trust the own/mechanic.)

A year after that…

I took it back to the shop cause it started leaking REALLY badly.
He pulled the transmission and replaced the front pump seal.
This is the point where I likely should have rebuilt the transmission, because pulling it was expensive.
(leak was better, but still there)

A year after that...

I towed a three rail motorcycle trailer (loaded) about 3 hours each way on a weekend. After that:
It started late shifting again, but only for 1st gear. It only wants to shift into 2nd at around 25 mph, where the engine is revving up good, and then it shifts very hard into second.

Back to the shop:
They "serviced the trans" again and replaced the shifter shaft seal (no more leaking!)
Still shifted really late from 1st to 2nd.
I drove it for about 45 mins on the freeway, to a campground let it sit over night, drove 45 mins on the freeway again, and when I got back to town it started shifting "Normal"(see above) again.

I have taken this truck three times to a shop (same one) and each time they have stopped one leak
(and done the services I mentioned above). Front Pump seal, pan, shift seal. The leak seems to have stopped but the trans is not quite right.

I have just started to educate myself on these transmissions which were always a "black box" to me.
The guy at the shop says it's time for a rebuild, an gave estimates for rebuilt trans from $1500 - $2100 installed with varying warranty levels (most expensive was 3 years from Jasper).
So thats $1650 for the Trans plus $3-400 installation.

The reason I don't like the "just rebuild it" strategy is that it does not tell you what is wrong.
The trans *works* it has not failed, and now it is not leaking.
The trans does not slip, and what it does is not shift right. I have this strange feeling in my
gut that I can actually fix this thing.

My current theory is that the Throttle Valve cable, or "throttle valve" is bad.

What about the "Shift Improver Kits" from B&M?

I found this good article on how the Throttle Valves work:
Throttle Valve 101 [http://www.tvmadeez.com/article/index.php]

I hope this long winded post helps to explain where we are and is not just rambling.

I would like advice from 700R4 Gurus here, I feel like it's worth the time and money to fix it right.
Now, if my mechanics would just feel that way!
--Nick