# 1997 gmc sierra 3500 won't go over 98km/h



## duramax-king (Oct 29, 2009)

hi guys i bought a 1997 gmc sierra 3500 not to long ago and i was told it needed a tranny shift cable, so i replaced it and tried it out on the highway and it still won't go over 98km/h, does anyone kno what this could be?
Sorry it's a 6.5 turbo diesel with auto trans.


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## CT-TILEMAN (Jan 3, 2009)

There is a factory speed limiter, it will need a custom ecm reflash to remove the limiter.


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## VPRacing (Dec 26, 2009)

98km/h is like 60mph... Theres no way it would have a 60mph governor.

Is there a factory tach? If so, what RPM is the engine running at that speed? Sounds like it could be something to do with the trans cable in a lower gear. Although I thought they had shift linkages???


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## no lead (Dec 10, 2008)

sounds like your not shifting into the final gears.


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## duramax-king (Oct 29, 2009)

i replaced the linkage that shifts to the tranny, and it shifts into all gears.does anyone kno where i can get a custom ecm reflash, or other way to remove the limited.


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## Steve G. (Jan 18, 2009)

no lead;938880 said:


> sounds like your not shifting into the final gears.


ditto, this is what i thought first.
I would get the book for our truck and adjust the shift cable properly.


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## duramax-king (Oct 29, 2009)

the transmission shifts into all gears.it just won't let me go over 98km/h, if i try going faster it just drops a gear and then goes back up and speed doesn't increase.


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## no lead (Dec 10, 2008)

has it ever gone more than 98 since you bought it? or were you told that is why you needed a trans cable? maybe a throttle cable issue? ever change the fuel filter?


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## CT-TILEMAN (Jan 3, 2009)

Did not see it was KPH and not MPH, I know the USA trucks from GM are all limited to either 96 or 98 MPH.

Hope you get it figured out.


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## duramax-king (Oct 29, 2009)

no it never went over 98 km/h, and i was told it need a trans cable so i changed it, still won't go ofer 98.could be the throttle cable, will also try changing the fuel filter.


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## dheavychevy38 (Nov 19, 2008)

x2 on the rpm what are they ? What gear ratio does it have ? I had a similar problem with mine and it was a trans issue but the rpms where through the roof.


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## hydro_37 (Sep 10, 2006)

RPM's and gear ratio would help figure it out more


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## adksnowo (Dec 14, 2005)

Is the turbo spooling up? Maybe there is no boost? Leaking fuel lines or fuel pump shot (not enough fuel pressure)? Exhaust or turbo ducts leaking?


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## duramax-king (Oct 29, 2009)

rpms are close to 2700-2800, and everything else is good, i think that someone might have put a speed limiter on it (the previous owner). does anyone know how i can get the limiter off?or check if there is one?gear ratio is 3.73, i think but i'm not quite sure?


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## NICHOLS LANDSCA (Sep 15, 2007)

Is there a check engine light? Does it pull up to 60 and then fall on it's nose? Need more info than it just won't go 60. BTW there isn't a throttle cable.


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## duramax-king (Oct 29, 2009)

no check engine light on, it goes to 60 then if you want to go faster it just won't go.the truck drive normally until around 60mph and then when you go to speed up it shifts down and then a moment later it shifts back up.


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## drp (Oct 12, 2009)

The RPM is way to high for 3.73 gears at 98km/hr.

Ford 2004 6.0 auto 3.73 gears 98 km/hr = 1750 rpm

yours sound way to high.


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## VPRacing (Dec 26, 2009)

Sounds like the 1st/2nd shift solenoid keeps turning off not allowing the transmission to shift into overdrive... Probably going to need to take it in unless you're a decent mechanic and know about automatic transmissions. 

There are 2 solenoids: 1st to 2nd shift solenoid and 2nd to 3rd shift solenoid.

1st gear - 1-2 shift solenoid is ON, 2-3 shift solenoid is OFF
2nd gear - 1-2 shift solenoid is OFF, 2-3 shift solenoid is OFF
3rd gear - 1-2 shift solenoid is OFF, 2-3 shift solenoid is ON
4th gear - 1-2 shift solenoid is ON, 2-3 shift solenoid is ON

In case you want to try to tackle this yourself, I'd start there...

This is all in regards to the shift linkages being correct and not bent.


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## duramax-king (Oct 29, 2009)

ok so i went to my mechanic finally and he told me the gears are to low...? does anyone know what gears were availble in those years? or how to check your gears?


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## Plowtoy (Dec 15, 2001)

duramax-king;962309 said:


> ok so i went to my mechanic finally and he told me the gears are to low...? does anyone know what gears were availble in those years? or how to check your gears?


I would suggest going to a dealer and have them run the V.I.N. They would be able to tell you the ratio from that. Also it should be a 4l80e trans behind the 6.5, I don't think there's a shift cable either since the throttle is "fly by wire" and the computer controls the trans. Good luck


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## dheavychevy38 (Nov 19, 2008)

My personal truck is a 97 k2500 with a 6.5 4l80e and 4:10. Many of the trucks I work on are 3500 or 3500hd 6.5 with 4l80e trans. I have seen anywhere from 4:10 or 4:56 in them. If you haven't done anything to the rear axle yet you can service it and find out what the gears are by the numbers on the ring gear.


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## PeterD (Jan 13, 2010)

duramax-king;938646 said:


> hi guys i bought a 1997 gmc sierra 3500 not to long ago and i was told it needed a tranny shift cable, so i replaced it and tried it out on the highway and it still won't go over 98km/h, does anyone kno what this could be?
> Sorry it's a 6.5 turbo diesel with auto trans.


6.5 with a 4L80E? First thing is to put a good scan tool on it, one that will do live data. A Tech II is best (but they are not common) or an AutoEnginuity PC based tool. Look at the live data, and that will tell you what's going on.

It is unlikely that it is a speed limiter, I'd guess it is not in the right gear. But, at 98 KM/H what RPMs are you reading? Probably should be between 1800 and 2200 (depends on gears).

There is always the possibility that it is engine related. One common failure is the PMD. (My company is one of the largest aftermarket PMD Cooler (heat sink) makers, so we do get a lot of experience with them). But usually a PMD just causes the truck to either stall, or not start--rare to see it affect performance.

Also, when was the last time the fuel filter was serviced? They should be changed on a regular basis. Also, one more thing, if you are running bio, stop running it for now, and make sure that's not the problem. I've found with my 6.5's that bio in the winter is a big mistake. OK in the summer, but once the temps drop below 40 or so, the stuff starts causing problems. (Just my experience, YMMV).

Also, while you have the scan tool on for the live data, check to make sure there are no codes (DTCs) being set. If there are any, post them.


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