87 GMC issues

[Captain J]

Hi all, I own a 1987 GMC Sierra 7.4L. With fuel injection
I just done a complete restro, however I need your help in:
1. Gear shift’s at high speeds, I suspect the MAP, how do I fix it.

2. The reverse light will not come on when gear in reverse (auto trans),

Any thoughts
Thanks����

[Captain J]

Some 70+ viewers and not a reply ��?

[Sabaka454]

Originally Posted by Captain J

Some 70+ viewers and not a reply ��?

Probably because it's not clear what you are asking.

1. Gear shift’s at high speeds, I suspect the MAP, how do I fix it.

What are you saying?

2. The reverse light will not come on when gear in reverse (auto trans),

Check the PN switch on the column and it's adjustment.

[Captain J]

Thanks Sabaka454
Maybe you’re right, my question
When driving, the gear will not shift from 1st to second at low speed (as normal), it shifts at higher speed 30-40mph, otherwise it will stay in 1st gear.
What causes the gear to shift at higher speed? Is it the MAP sensor which I recently changed? Or something else?
Nothing was done to the transmission.
Only the TBI, was overhauled
I hope it’s clear.

[foamypirate]

Originally Posted by Captain J

Thanks Sabaka454
Maybe you’re right, my question
When driving, the gear will not shift from 1st to second at low speed (as normal), it shifts at higher speed 30-40mph, otherwise it will stay in 1st gear.
What causes the gear to shift at higher speed? Is it the MAP sensor which I recently changed? Or something else?
Nothing was done to the transmission.
Only the TBI, was overhauled
I hope it’s clear.

You are possibly missing the vacuum line to the vacuum modulator. With the line disconnected, the modular sees no vacuum, and assumes you have the throttle wide open. I'd check there, first. This is assuming you have a TH400 (my guess, due to the 7.4L big block).

Reverse lights, as mentioned, are operated by the switch at the base of the column, inside of the cab. It's adjustable by loosening the screws and moving it around. It may take some tinkering to get it just right.

[Captain J]

Foamypirate, thanks for your reply, both issues were fixed in seconds.
I found the vacuum line was disconnected from the vacuum modulator.
The reverse light switch was pushed all the way in, I moved back and it works.
Again thanks.

[foamypirate]

Glad to help out!

[LT7A]

Captain J, speaking for myself, and probably many others, we're happy to help if we have ideas that can help. But if you got a restoration going on (or done), we'd really like to see your truck. It's a good way to get people involved. Kudos to Foamypirate (what does that even mean? Ha.) and it's cool that you got your truck fixed. Now maybe we get to see it?

[Captain J]

Thanks LT7A for your kind words, my truck restoration is done, however the electric part of it still not working properly, especially the fuel tanks. My electric experience is basic, and I’m trying to see why one tank is supplying fuel, and sometimes the other tank is supplying fuel. Also I found that some emission systems are plugged, not knowing why, but I’ll get it the electric part fix soon, then I’ll share some pictures with you. Thanks

[Captain J]

This is my truck after restoration.
It’s a 1987 GMC Sierra, 7.4L 454 engine, automatic, fleetside, with 47800mi.
Note I’m 2ed owner, truck has no history of accidents, no rust, just some engine issues which I had to rebuild.

I repainted the truck same color (cosmetics paint), bedliner underneath. Changed the torn vinyl seat with new velour seat, changed the black rubber floor mat with new molded carpet same original color tan. Installed new cloth headliner, completed interior (pillars, dash), roof marker & cargo lights, changed the front grill from single head light to dual lights, restored the front grill with emblem, all items are from LMC except the roof marker & cargo lights, grill & emblem.
Sorry I can’t upload more than 5 pictures,
Enjoy

[85/Silverado]

Nice and clean for a Antique.

[Ski-me]

Isn't there a TV cable adjustment?

[Captain J]

Thanks 85/Silverado, only disappointment is the dash cover, didn’t fit well.
Ski-me, I’m not sure I understand your question?

[Ski-me]

There is a "TV Cable" adjustment for your transmission. If it's not adjusted correctly, it can create some transmission shifting problems. It's up by the TBI unit in the engine bay. I'm assuming the 400 Turbo has one like my 700r4.



Although I found an OEM dash, I did look at and compared a "dashesdirect.com" dashboard. IT was very similar to the OEM one I purchased. Still need to paint it with vinyl paint though.

[Captain J]

Ski-me, oh ok, I resolved the shifting issue, it was a disconnected vacuum line from the vacuum modular, near the transmission, thanks to foampirate.