Weird problems

[mdrburchette]

I took my 71 out for my errand run today and while I was on the highway and accelerating to get by a BMW, I noticed a resonating feel coming from the car. It's hard to explain because I couldn't hear anything unusual and I wasn't experiencing any vibration, but I could sense a low resonating sound/feel/whatever possible coming from the drivetrain. It only happened while accelerating medium to heavy and when I let off gas and eased back into it, it went away. What could it be? I had visually checked the donut a couple months back while laying under the car in my living room. Could it be from the driveshaft?

I also noticed my temp gauge acting weird. I'm sure it's totally unrelated since I noticed this when the other problem wasn't evident, but the temp gauge would read around 200 degrees while driving, then it would act like something let loose and it would drop down to 180. It didn't make a difference if I opened the heater valve but while idling, it maintained a temp of around 180 - 185 without wavering. Thermostat sticking maybe?
You know something's bound to go wrong since Ron just left for a 3 week stint to Atlanta.

[So Cal Mark]

I'd look at the u-joints, or possibly a rear bushing letting the axle twist.
erratic cooling usually means air in the system, but loose/dirty connections to the sending units can cause some weird stuff

[mbouse]

two years ago, i had a profound noise whapping me only on hard accel and right hand turns...
turned out to be a broken center support bearing BRACKET. Why that bracket decided to break...i dunno.

and i would imagine you already ruled out air in the coolant, so my bet goes to loose or dirty sensor connections.. or a sensor gone bad... not unlike GIRLS GONE BAD

[rlux4]

All good suggestions. The only thing that strikes me to check would be the four bolts where the drive line attaches to the rear end, and the bolts on the guibo for snugness.
Ron

[ventura ace]

. . ., but I could sense a low resonating sound/feel/whatever possible coming from the drivetrain. It only happened while accelerating medium to heavy and when I let off gas and eased back into it, it went away. , , ,:?

D, was the rumble at any particular speed range, . . . or at all speeds?

Alvon

[mdrburchette]

Alvon, I didn't notice it except on the highway going around 70 and that was only during medium to hard acceleration. In fact, I tried to make it happen in different gears at slower speeds, but it didn't happen. I noticed this last weekend when I met up with some car buddies at the racetrack. Since I was on rural roads, I was only going 60.

[ventura ace]

The reason I ask, and you may remember that I've talked to you about this before, is that I have a similar rumble /resonance /vibration that I've never been able to pin down, and I suspect that it is drive shaft unbalance. My rumble comes in from about 78 - 80 mph. Not at lower speeds, and not at higher speeds. I've had different wheels, tires, rotors, rebuilt the rear end with new bearings throughout, new bushings in the suspension, new u-joint, new center bearing and rubber isolator, new guibo, and rebuilt the tranny with new bearings throughout. Some of these things have reduced the rumble, but never eliminated it. I believe it is the drive shaft out of balance, and if anything else has any looseness at all, it helps amplify the vibration, so that is why these maintenance fixes have improved but not eliminated the vibration. I've noticed this same rumble in many other spiders at similar speeds, and I can't remember if I noticed it with your spiders when I've driven them. Do you remember? Your CRS is not quite as bad as mine!!

Alvon

[mdrburchette]

I doubt you heard/felt it in mine last time you drove them, but you will next time in the 71! I'll just drive it and see if it gets any worse after I check underneath to make sure everything is good. It'll be hard to diagnose since it only happens at higher speeds and acceleration.

[stefhahn]

One thing that can easily be checked (ok, when crawling underneath...) is the central driveshaft support - the rubber in there has the tendency to disappear/crack - and the symptoms then sound like the ones on yours i.e. I had when mine went...
ciao,
Stefan

[ga.spyder]

Hey Denise,
at FFO I had the same problem w/ the temp guage.It would go up to 200+ ,then suddenly drop down to normal.I had a suspect connection at the sensor ,and I also disconnected the overheat sensor.The problem immediately disappeared.
Craig

[mdrburchette]

Thanks for all the suggestions. I'll drive it and see if it gets worse so I can at least diagnose the drivetrain hum, but I'll roll under it to see if anything pops out at me. As for the cooling system issue, I'll clean the connections and see what happens. I don't think I've heard the fan run recently. It's been a while since I tuned the IDFs and the fan comes on at the most inopportune time then.