What would "HD Trailering Special Equip" be on a 1990 GMC Sierra Club Coupe SLE K1500 5.7L Auto Trans?

[first_truck]

Curious what "HD Trailering Special Equip" would be on this truck. I'm not a truck guy. Bought this recently and it still has the original window sticker. One of the upgrades (for $448) was "HD Trailering Special Equip." Any idea what that consisted of? I did some Google searching with no luck. Thanks!

 

[Wes Harden]

if you can find the "RPO" code normally on sticker found in glove box. we can look up the option better.

Tow packages Normally up grade the cooling system, lower ring and pinion gear ratio, add a hitch and wiring, plus an electric trailer brake control in cab.

 

[tarussell]

The OEM’s use the term “H.D.” rather loosely on any/all models and/or years.

Example, got a 85 K-5 that the SPID sheet lists an RPO for a H.D. TRLR PKG that according to my local GM parts department hardcore geek says lists all the following:
factory ( not dealer add on ) installed receiver.
OEM trailer wiring harness
H.D. Flasher relay and fuse
higher weight rating on rear springs
engine oil cooler
H.D. Radiator with integrated trans cooler.
H.D. fan clutch and a more aggressive pitch fan blade ( still only a five-blade fan but it was obvious that the pitch was more then other GM truck five-bladed fans ).
Larger rear brakes ( I think the shoes were wider but they looked the same as most others of the time period ).
And finally a 3.73 gear ratio

Also had a 1986 K-5 with and engine oil cooler and 3.73 gear ratio and a five blade fan with less pitch a std radiator with integrated trans cooler and a std receiver but none of the other stuff.
This truck came with a receiver , cooler and gear but did not have the complete “package“ as the 85 K-5 does.

Some of these options could have come individually but certain codes made the combo mandatory.
Like Wes said breaking down the RPO codes reveals much; just keep in mind that an “H.D.“ package on a half ton truck could mean upgrades such as a larger rear axle ( on later model trucks ) and bigger brakes among other things but it’s still a half ton truck - packages vary in content depending on what model is selected.

 

[scouthead]

I'm guessing it has a 6 lug semi float 14 bolt rear end??
probably has an engine oil cooler and the adapter between the block and filter that the lines connect to?

 

[Bigb55]

Should have a larger radiator and trans cooler.

3.73 or 4.10 gears

Stiffer rear leaf springs and different rear shocks.

A larger alternator

Hitch and trailer wiring.

And the G80 LSD.

That would be about it for the early 90s.

More then likely it would be equivalent to a Z71 and tow package. Possible it was a combo package deal.

RPO codes will tell the story.