Jack71

Okay, I cruise in 3rd gear everything is cool. I hop the the highway for a few miles and drop it into OD. Wow, look at me go.

I get off onto some backroads so I drop back into 3rd, which is fine for around town. Now everytime I take my foot off the gas pedal there's a thump from transmission and the rpms drop / car slows quickly. It does not "coast" as it should. Now it doesn't come to a screamin' stop or anything like that, but its enough to say "WFT is wrong here?"

I know lots of guys had success with BTO tranny's, but this one has been a PITA since I got it with leaks & now this. :rant:

Magnum '82

Can't say that I ever had that problem. Mine would just slip bad in 3rd & 4th. Had a extensive kit put in at rebuild and it has been fine since. The 3rd & 4th plates were burnt, which I am told this tranny was good for. Good luck.

BSeery

if it is slowing quickly it sounds like the torque converter is locked, and is not unlocking when you press the brake or decelerate.

Just a guess.....

Jack71

That's crossed my mind too, but its moving thru the gears ok and if it was locked I'd expect a nasty bog or cause it to stall the motor. I don't know. Any other ideas?

The Money Pit

Jack,
How long have you had the transmission?Have you contacted BTO for assistance?Just curious if you had better luck than I did with them.

Larry B.

700R4's don't "freewheel" in manual 3rd. I don't have a book handy but I had the same thing with a 92 when it was in manual 3rd. I had the factory service manual for the car and there was a complete 700R4 section. I looked at the flow chart and found that there is a difference in manual 3rd and 3rd when it is through OD. I think you are feeling the T.C. locking. What happens when you touch the brake? Tap the brake and see if you can feel the T.C unlock. When it engages/dis-engages it feels like a bump as opposed to a shift.

Jack71

I wouldn't even bother putting a warranty claim in with them. If I go through the hassle of taking it out, shipping it, dealing with their excuses, installing it, only to have it not right -- I would rather stick bamboo under my fingernails and play the piano. :nopity

They told me they have less than a 1% failure rate. Well, that is quite a misleading statistic.

I just want it to work. There's big risks associated with using big vendors vs. your local shop. I learned my lesson and went local to build my engine.

Jack71

I do have the TC wired thru my brake pedal. But this problem occurs throughout start & stop driving. I'll have to play with more and see what conditions cause this behavior.

Sorry to rant, but these things are frustrating. I'll also call BTO and see what they say (I'll should give them a chance before I dump on them anyway).

The Money Pit

I hear you loud and clear.Already scoped out the shop that'll be rebuilding my trans.He's got 25+ years with performance transmissions,and his dad has 40 years.The shops only 20 minutes from me,so if problems arise..."I'll be back!" :cool:

Jack71

Money Pit -- thats great, did you get a level 2 from BTO?

There's a well-known shop in NJ called Level10. That's probably where I'll go.

The Money Pit

Mine was a level 3.You know the bullet proof transmission one step below the super nitro model.Mine shifted late from day one,in fact I backed the TV cam down to soften the shifts the first day I drove it.I emailed BTO no less than 6 times,and to this day have had no response.
After driving for a distance on hot days I notice the shifting gets weird.Sometimes it wont downshift when I come to a stop till well after I stop.Sometimes the upshift is way late.After a few miles of easy cruising,the shifting goes back to normal,but I suspect I'm still slipping in 3rd and OD.One blip of the throttle and the tach will swing from 2500 to 5000 like was in neutral.
Hind sight is always 20/20.

Jack71

Me too. Complete stop is fine, but it won't downshift if its still rolling.

:iagree:

mrvette

OK, some 5 years ago I did my own 700r4 install after having it built by a pro....and if you examine a GM manual on them....like my '87 vette manual you will find the tranny has about 15 or so possible configurations for the torque converter lockup....and it cam make a huge differance in the trannies' performance feel....for sure....

now some of the original factory configeration have it lock ONLY if it's in 4th gear.....MY tranny will lock in 2-3-4 but of course not first....

SO with that information, I tried just feeding a steady 12 volts to it, and grounding the computer controll unit.....which IF the internal switches say so, as they are in series with the internal electrical controll solenoid, it will more or less permanently lock the converter, and wne stopping, even if the tranny was supposed to downshift eventually to first, it would stall the engine....
like a stickshift with clutch engaged, and in gear....

SO I put a controll relay in that 12 volt line, wired so that it's action is just the opposite of the brake lights....meaning if the lights lite, the 12 to the tranny goes zero, that makes the tranny unlock....gotta check that is happening....
second off, if the tranny is locked and in manual 3rd gear....it sounds as if your tranny could be normal.....offhand....there is NO slop if the converter is locked up....NOW depending on your speed and type of controller for the ground end, and how it's set, yes, it's possible to have the engine rev one hell of a lot on a downshift, and a sloppy converter, 2-2.2k slop is stock vette stall speeds, and I personally did not like it that loose for street driving, as things allways felt too indefinate, and so I"d keep my computer flippout of the circuit via a consold switch, and then it was allways locked, soon as 2nd gear was hit, and stayed locked through 3-4......and of course when I tore the thing down 2 years ago for a 3/4 clutch pack, burnt, and noticed the 2/4 band was ripped up metallically....mounting points torn and ripped, and the engage point of the pin was stabbed too tight, I figgered on getting a truck converter, bad for drag racing, but feels better for performance street driving....the listed stall on my converter how is about 1200 rpms.....so with a 800 rpm idle speed, yes, it's in neutral at lights....

I NOW leave the console switch in computer position, meaning it is programmed off the TPI computer to lock at 50 mph.....

and that's the way I run it now a daze, very seldome if ever in the 'manual' mode, as above....

so anyway, that description with my comments should help you feel your way through, maybe with voltmeter aide to see what your operation signals to the tranny are under various driving conditions....

GENE

Jack71

Phew. Thanks Gene, I think...

I have a big head on my shoulders, unfortunately its mostly bone.

I'll reread this a few times, but I get your drift. Figure out what you're sending to the transmission and take it from there. And buy a good book on 700R4's.

mrvette

Jack, for a tranny guide, look in the phone book for a transmission supply shop and see if they carry the ATSG service guided, they are basically a reprint of my '87 vette manual right from GM....they list all the possible internal wiring diagrams,...and so....

realize the commonality IS....the brakes only ever kill the 12 volt feed to the tranny, totally unlocking the converter no matter what else is done....

the switches in the tranny are connected to the coil and then to the output, which is either grounded all the time, as if my switch was thrown, OR grounded at some speed (50 mph) in my car....by the computer, or if you have an aftermarket controller, you are on your own, as there can be a bunch of more or less acceptable methods of doing the job at hand...

GENE

arrio76

When in D3 the trans will not coast. It is designed to have engine breaking in 3-2-1. So when you move the selector from OD (4th) to 3 (D3) you should get an engine breaking effect. It will act this way, engine breaking, as long as it is in D1-D2-D3. :steering:

Jack71

This is much more than the expected deceleration when going from 4th to 3rd (or any lower gear) And is doesn't happen when I move the stick.

Its feels like popping the brake briskly for second. It must be related to the convertor somehow.