Top end shifting weird....

[Tunez]

When I get to higher speeds the car tends to shift funny, as in it can't seem to make it's mind up which gear it needs to be in. Also I hear many people saying the SHO will dart up to 140MPH and mine seems to not be very strong above 80mph. Seems like there is just some lack of power and pull.

For reference, the SHO is a 98 with ONLY 30,000 miles. I noticed it the most whiling riding down the highway at night and playing with a Lexus LS400 and getting my ass handed to me on a silver platter from 75mph up. Now in the neighbor hood of 55mph up to about 80mph I could walk off pretty easy.

Does it sound like major tune up time or what?

Also, my current mods are as follows:
3rd cat, stock flex pipe, and front muffler replaced. The factory rear mufflers are replaced with Flow Master mufflers.

I also have the Open Air Cone filter mod done. It is around 40 degrees here at night now so the engine compartment is relativly cool as well.

Any help would be appreciated. Also, I would like to know the next best route to look to as far as performance steps go. I know a couple of you guys have gone pretty far with the mods and have probably learned through trial and error which are the best for the buck.

Thanks in advance for your replies guys.

 

[rjensen]

Yup, mine seems to be a bit indecisive as well. My sense of it is that the converter is going in and out of lock. Actually it seems to unlock sooner than other cars. It seems to "free-wheel" more than I'm used to. I'm wondering, too, if this is normal.

rj

 

[SHODWN]

Tunes, try this (im serious) go out and unplug your battery, let it sit for about 10 mins, plug it back in and go for a ride. take a few high spped runs, shut it off, then take it and drive around in second taking it to redline a few time but make the motor pull all the way up to red line and let off.

do that a few times, then shut the car off again and re start it (totall of 5 times) then take it up to the speed your talking about. if its still slow I would check your IMRC plates for proper operation. if thats all ok then take the flexi hose off of your throttle body and see if it looks wet (the TB) from oil. it sounds like you could use an intake cleaning but with only 30k that is very odd.

Rjenson, you should not have any freewheeling, the trans has a feature that act like a trans brake. if your freewheeling something wrong or will soon be.

 

[SHOZ123]

if thats all ok then take the flexi hose off of your throttle body and see if it looks wet (the TB) from oil

From my PCV catch can experiments I have found that plugging this 3/8" line, the one going from the pre-TB hose 3" flex hose to the Tee where it then goes to the valve covers, will greatly reduce the amount of gunk going through the PCV valve. With this hooked up OEM style and especially in the cold weather there is a great amount of water vapor introduced into the crankcase.

If this is plugged the crankcase is under a constant 7-10" of vacuum which will improve your performance and fuel mileage while at the same time reducing the sludge ingested into intake.

 

[MilTownSHO]

My moms 98 SHO JUST hit 30,000 and it still flys up to speed with no problem. Sometimes though, not lately, it seems to not go as fast as it used to when you step on it. I already did the little 30,000 mile tune-up thing for her so it cant be that.

 

[OzzmanNT]

No power past 80mph....something is definatly wrong. Go with what kirk said definatly.

Mine pulls like a **** at 80 and up.

It's them flow bastards that's it wink

 

[Tunez]

OK Kirk, did the first section and it seems to be a little better. Although, it still seems to do it just a little bit. Also something else I noticed after doing this was that at 80 MPH it does't seem to want to go into the highest gear and seems to tach a bit higher and hesitant to make the shift. It did that when I first got it and that went away after a while as well.

My next question is in reference to the IMRC plates.... What the **** is that!! I am not familiar with the abbreviation. Next, the intake cleaning, how do you do that and does it require a mechanic to do it?

I haven't checked the TB hose for oil yet as well. Will do that today if I have a chance. Is that hose plugging or reroute job a good idea here?

Alot of this could have to do with some mental mess of just wanting to go faster. After we can determine if there is a problem or not, I will see if you can suggest the next best performance route for me to take to get the best bang for the buck, seeing as you have done most of them. I have looked at pullies and even NOS as an option. Not really too excited about the NOS due to having to refill a bottle to have fun. Would rather spend a little more and have a "permanent" installed option.

 

[Evil Sneak]

before i got my trans fixed the car would barely move. like 110 was all she really wanted to do.

trans is now fixed. at 90 mph passing gear is pretty kewl. i let guys get nose upo with me at 90 or 100mph then punch it and leave em.

trans is def a huge variable.

am i supposed to be hearing chains at high speeds? i swear i hear those timing chains whirring.

 

[Ian Macoomb]

Tunez:
OK Kirk, did the first section and it seems to be a little better. Although, it still seems to do it just a little bit. Also something else I noticed after doing this was that at 80 MPH it does't seem to want to go into the highest gear and seems to tach a bit higher and hesitant to make the shift. It did that when I first got it and that went away after a while as well.

Have you tried doing a full throttle 1/4 mile run yet? Try it and see if it has any trouble shifting from 1-2, and 2-3.

Mine had problems shifting and would tach higher than it should on the highway. I finally got the infamous P1744 code "Torque Convertor Clutch Solenoid Performance". Turned out to be the pump drive shaft, bushing and bearing. Cost about $350 to have fixed.

 

[f150fan]

am i supposed to be hearing chains at high speeds? i swear i hear those timing chains whirring.

I don't know about high speeds because all I can hear is my exhaust and road noise...but at idle if you lean down toward the passenger side footwell you can herre the whirrrrrr!!

 

[wuzzzer]

SHODWN:
...then take it and drive around in second taking it to redline a few time but make the motor pull all the way up to red line and let off.

Wow, that does really make a difference! I don't drive my car too aggressively with the snow tires on, but tonight I wanted to drive it a little hard so the car didn't get too far into 'granny mode.'
I did what Kirk suggested, put the transmission in '2' and from a dead stop eased the gas until I was going 5mph or so then floored it all the way until redline. Of course, it took until 40mph or so to start really accelerating hard. Ran up to about 80mph or so, let off the gas and at the next light I made a u-turn, this time in 'D'. Wow! Pulling away from the light I noticed a huge difference in how hard both 1st and 2nd gear pulled, and the shift from 2nd to 3rd was at a much higher rpm than normal.
Very noticeable difference! thumbs_u Thanks Kirk!

 

[MilTownSHO]

If you drive a GEN III in the winter since you have to go slower for the most part, does it always go into granny mode and you have to drive it in 2 and then D like Kirk explained? Or does it eventually go back to how it should be when summer comes around and you can get on it more?

<small>[ December 15, 2002, 01:29 PM: Message edited by: MilTownSHO ]</small>

 

[wuzzzer]

From what I experienced last night, it seems that doing Kirk's 'trick' puts it into it's highest performance mode faster than just driving aggressively after a winter of easy driving.

 

[SHOZ123]

I have a quick disconnect plug on my battery. There probably isn't a week that goes by the battery does not get unplugged. This will set the computer parameters back to factory default specs. Over time the data tables will be mapped with info that conforms the car to the high and low operating parameters as reported by the various sensors.

 

[mholhut]

Tunez:
My next question is in reference to the IMRC plates.... What the **** is that!! I am not familiar with the abbreviation. Next, the intake cleaning, how do you do that and does it require a mechanic to do it?

Tunez,

If your car is dogging at those speeds, it's likely that the culprit is the secondary intake manifold runner control. If you remove the plastic appearance cover on the motor, there is a silver 5" x 5" box that sits on top of the spark plugs. Remove the screws for the cover and you'll see a cable that is actuated by a plastic pulley. These pulleys often break, leaving the secondary intake runner butterflies either open or closed. Seems like your car is starving for air at those speeds, so I'm guessing that it's closed.

http://v8sho.com/SHO/imrc.html

 

[Tunez]

It still sounds like the secondaries are opening and closing when it hits around 3800rpm and there is still the kick in the pants.

Also, oddly, like I said, it does good from 0 ot say 80 but when it gets in the neighborhood of 90 mph or so it is kinda like it doesn;t really want to PULL from there. It just goes into a more MODERATE pull like it shifted out of the lower gear too early.

This was really noticable when a Lexus LS 400, older model, pretty much tore me a new one from 90 up. I can't explain how dissapointting that was when my old Nissan NX2000 would have DESTROYED that car at those speeds and it was a 4 banger.

<small>[ December 17, 2002, 03:53 PM: Message edited by: Tunez ]</small>