kael

Hey all, let me know if I'm using the wrong descriptions!

I finally hit driving time after a long winter of work on the engine, now seeing a problem with upshifts from my '87 automatic.

Scenario is pretty simple, in drive, accelerate at moderate pace from 0 to 30, on 1->2 upshift the car feels bumped forward, like the shift has no cushion. In manual terms, like a hard shift. Tried downshifts, big jerk on that, not smooth at all...typing that makes me think the problem is a key component of the transmission, shift should be cushioned.

Upshifts are bumpy enough sometimes the rears lose traction driving straight, 1/2 throttle or so. Didn't do this last year. Changed fluid last May. I've checked the fluid, looks good, levels fine.

My other thought was it might be my shaft u-joints going south, full or half.

Opinions? Sucks for me, been chasing rebuilding the top half of my engine and now this.

confab

Was your TV cable disconnected during the engine work? Did you hook it back up?

Because if the 700 is built properly, and that cable is left off or if it breaks, there is a ball that pops up in the VB and jacks up the line pressure to save the trans from burning up.

It will shift VERY HARD if this is the case.

kael

Yes, disconnected, re-connected and adjusted.

Would it shift hard in all gears?

confab

Adjusted properly? Ideally, it should be adjusted max tension at WOT.

arbee

If it was fine when you parked it but now shifts hard after you worked on the top end, the odds are the TV cable has a problem somewhere. Any kinks? Cable housing is mounted correctly?

kael

I tried the FSM method, move to short and slowly WOT. I'll try again with an extra foot so I can check the tension.

kael

Ah! Finally made it!

Now shift 1->2 is also butter smooth.

Key change was re-adjusting TV cable per FSM. Then taking it a little bit extra. I noted that at idle, the wire still had a bit of tension on it, this small move freed it.

What made me consider also:
http://www.superchevy.com/how-to/651...ting-tv-cable/

I don't think FSM adjustment is the end-all be-all adjustment. Could be my change accounts for a springy cable.

I'll chase specific speeds next, maybe move back a tiny bit. I know too loose can be a problem, already confirmed detent at WOT is good.

arbee

You need to put a pressure guage on it. If you have slack in it and it doesn't build pressure the minute you increase throttle, it is not set correctly.

confab

Cool! Glad you got it!

Be careful with that cable though. Basically, these transmissions were hybrids. They're on their way to full computer control, but they haven't arrived yet. That cable does the job the Vacuum Modulator used to do, (Matching transmission line pressure and rate of rise to engine load) and if it is too loose you will burn it up for sure.

Silver85

So would you say better to have it shifting a tad firm rather than too soft?

steven mack

Follow the factory service manual procedure.If the cable is not in the correct position you can smoke your trans pretty quick.The detente cable is not for adjusting your shift positions.

confab

Oh yeah. I absolutely would.

The TV confuses people because on other vehicles if you see a TV adjustment it is there to run the Throttle Valve pressure up and down to fine tune shift points. Like, you want a 1-2 under moderate throttle between about 18 and 22 MPH, 2-3 at 30 to 30 mph, etc. And it is fine to do this.

The thing with the 700/4L60 is that it is hyper sensitive to the TV cable setting. If it is loose, even a little, it will drop line pressure and if you do that in the 700 the 3-4 clutch burns up almost immediately.

I mean it is so sensitive we built a performance unit for a TPIed 57 chevy once. It had some fancy, aftermarket, aluminum throttle brackets and polishing and all the dress up stuff, and the mounting hole for the TV cable was a little bit too close to the pivot point for the throttle body. Although the pressures were fantastic at idle and WOT, it STILL burned up in a few miles because the rate of rise was off, and it was only off by a little bit. Move the cable mounting stud and it was fine! Still running around out there today.

So, it is very sensitive and for that reason I adjust it to max tension with a helper holding WOT and leave it. If shift points need to be adjusted that can be accomplished in a variety of other ways, as can shift firmness. Any other car? You'd jack it around to get the timing right and it would be fine. You try that with a 700/4L60 and it is just as likely to create a problem where one didn't exist previously.

Other people may feel differently, but I've been doing this a long time and based on my experience, that is the way it should be done and a little firm is WAY better than too loose.

IMVHO.

kael

No worries, I will chase for sure! The first couple of butter shifts and I was already thinking "Oh no, is this worse?!?".

Any other items to check other than pressure test? I need at least few drives before chasing what pressure gauge I need and how it connects....again. Lot of work since Xmas for a newbie.

arbee

Do some research and reading. You will understand. All legitimate data backs up what confab said. The 4l60 is a tempermental animal when it comes to the TV. The factory manual and professional experience knows a little bit more than your best friends aunts sisters husband who used to rebuild them in the prison workshop.

catso

Yeah! I think he built my trans too!

steven mack

Had a friend adjust his cable wrong and smoked the trans in less than 3 blocks.Stick with the factory service manual adjustment and don't mess with it afterwards.

confab

You're right about that, of course.. But I'm reluctant to tell people that on the internet because if they have their cable setting screwed up it is probably the last transmission test they'll ever perform.. LOL..

(Imagine the look on their faces? "Oh wow.. So, I guess the setting is WRONG then.. " LAWL!! )