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Old 08-04-2018, 12:55 PM   #1
56weav
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Join Date: Oct 2016
Location: Lincoln illinois
Posts: 33
Cruise control advice needed

Hello,
I have a 1986 GMC Sierra Classic short bed.
305v8 automatic. With ac , cruise etc.
When I bought this truck 2.5 years ago many things didn’t work and the p.o. wasn’t much of a wrench. That being said the cruise didn’t work , however,
I replaced all the vacuum lines adjusted the servo rod to the carb and it worked.
It had an issue or 2 but worked.
The issues were and are resume didn’t work and it occasionally wouldn’t hold speed up an incline .
One day while messing with the cruise going down the interstate , i tried getting the system to increase speed and the whole system failed. I replaced the control stalk and it worked again however it was still touchy sometimes it wouldn’t hold speed up an incline
And if you disengaged the system it wouldn’t always reengage .
That being said the system failed completely again.
All lines and the check valve, and servo hold vacuum.
Any thoughts out there ?
I am aware and have had new parts fail ( that’s the ac compressor clutch story it lasted 2 days )
Before I do my normal throw parts at it till it works I thought I’d ask
Thank you
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Old 08-05-2018, 07:58 AM   #2
Mattchu60
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Location: Swaledale, IA
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Re: Cruise control advice needed

I had various problems with my cruise control - mostly on mine it momentarily cut out and then come back to life. I replaced everything and nothing seemed to help. Then I finally replaced the control module that sits under the dash by the steering column and it worked great afterwards. Not sure thats your issue but its something to look at.
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Old 08-05-2018, 10:27 AM   #3
56weav
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Location: Lincoln illinois
Posts: 33
Re: Cruise control advice needed

Thank You for the mput
I’ll start with that.its would make sense it’s electrical in nature based on my symptoms.
With it holding vacuum everywhere it just didn’t lead to a vacuum issue
I was kinda of guessing the speed vvs that is hooked behind the speedometer
I’ll start with your input
Again thank you
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Old 08-05-2018, 02:55 PM   #4
hatzie
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Location: Wentworth, NH
Posts: 2,936
Re: Cruise control advice needed

The GM Cruise III Service tech training textbook is available in the manuals post.
It may just be a cheap Asian Cruise switch. No way to know without some testing.
__________________
1959 M35A2 LDT465-1D
1967 Dodge W200 B383, NP420/NP201
1969 Dodge Polara 500 B383, A833
1972 Ford F250 FE390, NP435/NP205
1976 Chevy K20, 6.5L, NV4500/NP208
1986 M1008 CUCV
2000 GMC C2500, TD6.5L, NV4500
2005.5 VW Jetta BRM PD-TDI, 02J 5 Speed
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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Old 08-05-2018, 04:34 PM   #5
56weav
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Join Date: Oct 2016
Location: Lincoln illinois
Posts: 33
Re: Cruise control advice needed

Thanks for the input
To the poor quality Asian parts I absolutely agree
This isn’t my first time restoring/fixing older vehicles. the quality of the aftermarket parts for these vehicles has been something of which could use improvement

After looking up under the dash I would guess the cruise box is to the right of the steering column and the left of the accelerator ?
Thanks for the manual links I’ll use them !
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Old 08-06-2018, 12:03 AM   #6
hatzie
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Re: Cruise control advice needed

Unfortunately Delco has been sourcing parts in China. They ride em pretty hard but the quality isn't what it was.
__________________
1959 M35A2 LDT465-1D
1967 Dodge W200 B383, NP420/NP201
1969 Dodge Polara 500 B383, A833
1972 Ford F250 FE390, NP435/NP205
1976 Chevy K20, 6.5L, NV4500/NP208
1986 M1008 CUCV
2000 GMC C2500, TD6.5L, NV4500
2005.5 VW Jetta BRM PD-TDI, 02J 5 Speed
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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