700r4 question plz help

[Oldskool153]

If im doing slow to normal driving my 92 goes into overdrive at 40mph the prob is that i think 40mph is too slow of a speed for the OD to be comming on, because when it comes on I can feel the rpms drop an more importanlty the car vibrating (because of the rpm drop, if that makes sense?) until I either get up to around 50mph or kick it down outta OD. Car has always done this but im wondering if 40mph is the right time or do i need to adjust then it comes on? Am i the only who who noticed this?

 

[G Winter]

I have a six speed and I have found that going into 5th gear (first of two overdrives I think it is .50 ) at 35 mph I look at the instant mileage and it goes up over using 3rd or 4th. By the time I get over 45 I get the best in 6th.
The 5.7 can easily pull this. Only drawback is when you need quick acceleration gears need to be changed on both auto and manual.

Glenn

 

[vetteoz]

If im doing slow to normal driving my 92 goes into overdrive at 40mph Car has always done this but im wondering if 40mph is the right time or do i need to adjust then it comes on? Am i the only who who noticed this?

Common reported problem.You may also be experiencing the convertor lockup as well at those speeds.Most leave in D until they get to higher speeds.

 

[John Robinson]

More Information Please

That is exactly how the Transmission was designed to work. What is the milage on the car? Is the exhaust the original system? With my 93 I had the same vibration problems and found I could eliminate most of it by working on the muffler bracket to tighten them up.

<a href="Corvette008.jpg picture by John-68 - Photobucket" target="_blank"><img src="http://i285.photobucket.com/albums/ll72/John-68/Corvette008.jpg" border="0" alt="Photobucket"></a>

 

[bill81vette]

I had an 89 pick-up that used to do that,
drove me nuts!!!!
It would kick into OD between 35-40 mph...:ugh:ugh
I found if i left it in drive around town and OD on the highways it worked much better for me!!!

 

[Oldskool153]

82k and its 100% stock, exhaust and all. Is it bad for the car or trans to have it in OD at the low of a speed? Or am i better to leave it in D then shift to OD like some people do? its just wierd having it go into OD at such a low speed ha

 

[vetteoz]

Is it bad for the car or trans to have it in OD at the low of a speed? its just wierd having it go into OD at such a low speed ha

The programming is for economy.Only bad if engine is lugging
I compare it to driving earlier non O/d cars; you happily drove around in top (3rd) no problems and they generally had lower (2.75+) gears compared to Vette 2.59's

 

[Oldskool153]

ok so i drove car out of OD around town and it was much better, I noticed that it feels like I can feel the car downshift more when comming to a stop than when I have the car in OD. is it in my head or is there a reason as to why I can feel it downshift more?

 

[shark454]

I too believe the torque converter is locking up ... as designed. The tranny rebuild guy said do my sporty driving is Drive, the OD is not robust enough either to handle too much. The Drive circuit is more stout.

 

[Oldskool153]

so that would be why the down shifting seems more crisp in drive then when i have it in OD?

 

[shark454]

so that would be why the down shifting seems more crisp in drive then when i have it in OD?

OD is designed to be the efficient way to cruise with MPG in mide. Performance driving in OD is really not what it is layed out for.

 

[John Robinson]

82k and its 100% stock, exhaust and all. Is it bad for the car or trans to have it in OD at the low of a speed? Or am i better to leave it in D then shift to OD like some people do? its just wierd having it go into OD at such a low speed ha

This is a subject that has advocates on both sides of the issue but I am reminded that before the car was ever released to the public It was subjected to months and miles of testing and the results were that the design was capable of being operated in O/D at that speed. If you live in a climate that gets cold you will note that the O/D does not engage until the speed is much higher and it will fall back to the lower speed when the transmission is warmed up. I cannot find anywhere in the owners manual were they say to only use D in town and O/D at higher speeds.

Part of the reasoning around using D in town goes back to the very early days of locking the converter and going into O/D was that there was sometimes a shutter when going into O/D. As I said this was a long time ago and the design problems they had then are long gone.

I still belive that you are in the wrong box thinking the transmission is the cause of your problem. Let me know if you are not able to see the picture I attached with my earlier post. That little fix eliminated my vibraton at low speed O/D to the point were I do not even notice it now.

 

[Oldskool153]

thanks i will try that this weekend forsure

 

[pgtr]

If im doing slow to normal driving my 92 goes into overdrive at 40mph the prob is that i think 40mph is too slow of a speed for the OD to be comming on, ... Car has always done this but im wondering if 40mph is the right time or do i need to adjust then it comes on? Am i the only who who noticed this?

More likely your trans is not going from OD (4th) into D (3rd) - rather the TCC is locking the torque converter - normally somewhere between about upper 30s to low 40s mph... Understand that it is ALREADY in 4th (OD) when this happens. It is common to confuse the lockup with the 3rd 4th upshift - there are also a number of variables here beyond speed to include engine load, pedal position and temperature.

No, there is no 'adjustment' AFAIK. If you circumvent the TCC circuit so that it sits in 4th and the TCC lockup does not occur - you can overheat the fluid. On earlier 700R4s that can be a bad thing.

It was intended under normal driving conditions that you drive the car with the selector in 4th (OD) around town or on the hwy. I believe this is stated in the owner's manual.

The FSM has full details on the operating characteristics of the 700R4.

 

[vetteoz]

If you circumvent the TCC circuit so that it sits in 4th and the TCC lockup does not occur - you can overheat the fluid. On earlier 700R4s that can be a bad thing.

The 88+ T700's with the upgrades has full flow to the trans cooler all the time; not just when TCC engaged as in the earlier trans so overheating is not a problem if running unlocked.No different than driving with a TH350 /TH400 which did not have a TCC

It was intended under normal driving conditions that you drive the car with the selector in 4th (OD) around town or on the hwy. I believe this is stated in the owner's manual.

I think you will find that is slanted toward fuel economy rather than any operational function.The owners manual for my 4+3 says to leave O/d engaged all the time where possible

 

[Hib Halverson]

It is true that upshift points at light throttle are all low in the interest of improving fuel economy, but there should not be any pronounced shudder or vibration.

If there is, I'd be looking for either a powertrain mount problem, a powertrain mount incompatibililty issue (ie: someone having replaced an OE rubber mount with urethane or, heaven-forbid, a solid mount) or an engine miss at part throttle.

 

[Oldskool153]

not an engine miss, becasue it only does it when it shifts into OD at low speeds (38-40mph) if i drive it in D, the problem does not occur. and its not really a bad vibration just enough to annoy me until i hit about 50mph then it goes away

 

[roger longman]

not an engine miss, becasue it only does it when it shifts into OD at low speeds (38-40mph) if i drive it in D, the problem does not occur. and its not really a bad vibration just enough to annoy me until i hit about 50mph then it goes away

Hi, You may want to look at my post, from a couple of months ago, entitled " Why the miss ", it describes the same symptoms as you are experiencing but the advice from the guys is different from that which you are receiving. It's fairly long but I think, worth reading. Roger.

 

[Oldskool153]

thanks, i read your post. Your problem seems differant from mine in that my car doesnt have a problem pulling, i can drive at below 50mph all day an as soon as a push on the pedal it kicks outta OD and goes. My vette guy is soppossed to look at her tommorow i'll ask him about it. also you have a tpi i dunno if that could make a differance becasue mine is an lt1

 

[93cruiser]

If im doing slow to normal driving my 92 goes into overdrive at 40mph the prob is that i think 40mph is too slow of a speed for the OD to be comming on, because when it comes on I can feel the rpms drop an more importanlty the car vibrating (because of the rpm drop, if that makes sense?) until I either get up to around 50mph or kick it down outta OD. Car has always done this but im wondering if 40mph is the right time or do i need to adjust then it comes on? Am i the only who who noticed this?

Its called Torgue Converter Shutter. The FSM talks abut this problem, by that you know it is a common problem. You need a new TC. From your description the TC lockup is working very well.

93cruiser
PS. I had the same symptons