Whaddya' think of the temperature spikin'?

If it's on the highway like he's sayin', tranny slips ain't gonna' let it overheat like stop n go drivin', huh?

 

Found this on the Corvette fever website...The temp sensor they're talking about is located on the front of the engine, above the waterpump.



Last driving season my 84 Corvette (with 4+3 manual transmission) had an overdrive problem. After the mandatory engine warm-up the overdrive would inexplicably cut out during the drive along with a “check engine” warning. Sometime later during the drive it would inexplicably engage with the “check engine” warning light going out.

A test with my $49.95 code reader yielded code no. 15 “Coolant temperature sensor or circuit fault - signal voltage high”. I took it to my local mechanic. He used his “professional” code reader and got 4 additional codes. He gave the car back to me and said “I’m baffled, I don’t even know where to start”.

After many hours studying the GM schematic diagram for this car, I discovered something surprising. There are two engine temperature sensors. One on the left side of the engine has only one wire going to the instrument cluster. The other on the front of the engine has two wires (twisted pair) going to the car’s computer. I had replaced the former a couple of years ago, so I focused on the latter. I removed it’s connector and inspected it. It resembled a coaxial connector, similar to cable TV. It seemed free of corrosion or dirt, so I reconnected it. As if by magic, the next time I drove the car the overdrive worked perfectly. It has worked perfectly ever since. Somehow the act of removing and reconnecting the front engine temperature sensor connector cured the problem.

 

rshiver, It doesn't jump out of gear. It clunks in and out of overdrive.the rpms will rise and fall as its going in and out of od. Thanks 4 the info i really appriciate it.

 

I'll try that.Thank you for the knowledge.

 

Cole, I'm not knowin' what you mean by clunkin' in and out of O/D... DO you mean the car lurches forward as you shift into the gear? Does it begin to slow down as the engine revs? And you're feelin' the stick do anything?

Exactly what happens? As many details as you can...

You wind out 3rd, let off the gas, push down the clutch, shift the linkage, release the clutch pedal, and accelerate the gas... Where in this sequence does the car lurch forward? Slow down? Rev? Re-catch???

 

I know exactly what you mean ,I have an 86 conv. with the 4+3 trans the overdrive is a separate unit controled by a few things ,the button on the top of your shift lever will manualy engage and disengauge the overdrive , it is also controlled by engine rpm throttle position and I believe engine temp. under normal operating conditions mine will shift itself into overdrive in second then if i accelerate it will shift down, this is the clunky feel you are getting . There is no dipstick for this unit and has to be checked like your manual trans by removing a level plug to see if there is oil in there.
I always push the button to disengauge the overdrive once it has kicked up into the higher gear, when the car is cold . When you mash thethrottle, the overdrive automaticly drops to low, just like the automatic transmissions, for passing.

First make sure it has the right oil level . if it does check for slipping at highway speed ( steady but fast enough to check engine rpm dosn't climb without speed climbing) if you put the throttle down fast at highway speed it shoud down shift, and when you let off it should up shift by itself . if you push the button on the top of the shifter it will maualy shift down and also up by another push of the button. ( the shift pattern on top of the shifter is the button)

Hope this helps,,,,Cheers

 

Cole, If you have a manual 1987, and it has a 4+3, the OD Selector switch is on top of the shifter. Lightly pressit down, and the OD will either go on, or off.

OD will only turn on in 2nd-4th. There should be a shift light that turns on, when rpm and vehicle speed sensors meet preset conditions. These sensors all feed data to the ECM. If all conditions are met, the OD switch will become enable through the ECM.

Some C4's had 6-speed manuals installed, as an aftermarket upgrade.

Basically the Doug Nash 4+3 Tranny is a T-10 4-speed, with a small two-speed automatic attached to the output shaft. The Doug Nash engraved the VIN # on each tranny. So if your needing repair, be sure to get yours back, if you are interested in keeping it #'s matching.

 

well i think i located the problem thanks to you all. The button on the shift stick is broke. Thanks for all the help; 86 IRON HEAD ,CRASH,CWB and RSHIVER you guys are great.I owe you all a beer.