main differences between 73-79, 81-87
 

I was just wondering what are some of the differences between 73-79 and 81-87 trucks. I know that the front fenders and grills are different but what other changes are there? Doors, beds, etc

??
 

I am wondering if the bed from an 86 will fit onto my 78. Will it?
Thanks,
Mike

the dash clusters and the dashpad a/c vents on passengerside and i believe the doors ar diffrent

Actually the breakdown should be 73-80 and 81-87.

Front fenders are different.
Hood is different
Hood cowl (where the wipers are) is different
Radiator core is different
There are differences in the shape of the dash pad and the bezel.
Various differences in gauges over the years.
Earlier year door panels are different.
Starting in 79 they started to use the gas door.
After 78 model years, they started to use cats.
Tailgate differences requiring year specific tailgate panel to be used.
Mounting locations for truck bed are different, I believe.

These are some that I know of...... :D

get LMCtruck to send you a catalog, they list every part year spec, its easy to see the difference in parts year to year. excellent resource.

An 86 bed will fit on your 78. You have to make sure the fuel door(s) location is the same though.

If I remember right it was 1979 when they switched to a lighter frame . The earlier trucks are more rigid .

piggybacking off Mitch...

* 73-78 headlight Bezels are the same, 79-80 bezels are the same...except some '80 models has square headlights and special bezels. Not sure about the diffs from 81+.

* 73-80 hoods are basically the same, except 79-80 hoods had a decorative "ridge" across the fron of theirs, while the 73-78 had a smooth front. 81+ are the same I believe.

* 73-76 doors, innards, & door panles are different than 77+...but all 73-87 doors will bolt on to any 73-87 truck, Blazer, 'Burb (also 88-91 Blazers and Burbs).

*Steering columns and intermediate shafts are different, not to mention the steering wheels. I believe the breakdown on the columns are 73-78, 79-83, 84-87. But...they all bolt in, it is just the wiring, intermediate shafts, wheels, and levers that are different (headlights, cruise, etc.).

* 12 bolt diffs were used up thru '81 I believe, while the 10 bolt was used thereafter.

These are just some of the ones off the top of my head. I know there are others, but this is all I have time for right now.

This is straight from LMC Truck which happened to be sitting next to my computer :)
1981-Hood and front feners were restyled for improved aerodynamics. Trucks lst up to 300 pounds through lighter glass, bumpers and body panels. On 4WD models, front quads shocks and automatic front locking hubs hat worked at speeds up to 20 mph were available. Electronic Spark Control was introduced on the 5.0L engine.

That's just the major changes. Other things include locking vent window handles introduced in like '78 or so, 1980 and up seats have reclined seat backs. If you flip through LMC you can see most everything is either 73-80 or 81-87, but the big things work universal like beds.

Ok my turn of what I remember.

The key years would be:
73-77 are pretty identical other then trim and colors and grill inserts.

In 78 you got th gas door and the door panels covered more door. Some stuff went electric like the oil pressure gage. In 78 there was a major electrical upgrade to the Blade style fuses. In 78 the rear seat passengers got a foot well and the rear seat became fold and tumble. In 80 Square headlight but still ahd the 73-80 fenders with vertical turn signal. In 80 or 81 electric choke.

81 new front clip with fixed cowel and truck lost weight with the lighter 208 aluminum transfer case, lighter built front clip, I hear that the gage of both body and frame was a little thinner. On a 4x4 the weight savings was around 340lb. It was about 200 on a 2wd truck. 305 made it's come back as well about 81. 700R4 overdive was a mid to late 81 addition as well.

87 was fisrt year of FI and only Year of FI in that body for the regular cab pickup. Crew cab, burb and K5 sontunied old bdy style through 91 to fufill goverment 10 eyar contracts to the Army that was signed in 81.
89 these trcuks got a cosmetic redew of the grill and interior. Re designated as the R for 2wd and V for 4wd in 88 to diferentiate from the new body.
in 90 they went to a tranny mounted VSS and electric speedo. in 91 the 4l80 showed up in the 3/4 and hlf ton varaints to replace the TH400.

4x4 stuff
The NP203's started in 73 and ran through 79. in 74 the NP203 was behind just about eveything including manuals. Pretty well the only year that was available. in 75 the NP203 was only behind manual transmission special order.

in 80 all trucks got a slip yoke 205 and 203 was discontinued. it carred a little into 81 and after that the 208 started.

241 replaced the 208 in mid 90.

about 83 the manual trucks went from Course 10 spline input to the stronger 40 spline input. about the same time they went to hydraulic clutch.

D44 was run through about 77 for front half ton trucks and then went to the 10 bolt front. in about 90 the to front went 30 spline.

D60 front showed up in 76. Before that you could NOT get a 1 ton 4x4. It simply did not exist.

The D60 was the first axle that could handle the 454 power and that was the first year you could get a 454 1 ton as well. Because the D60 was never installed in the Suburban you could not get a 4x4 454 powered burb in this body style EVER.

Think that has the big points.

[QUOTE=Grim Reaper]Ok my turn of what I remember.



In 78 you got th gas door and the door panels covered more door. Some stuff went electric like the oil pressure gage. In 78 there was a major electrical upgrade to the Blade style fuses. In 78 the rear seat passengers got a foot well and the rear seat became fold and tumble. In 80 Square headlight but still ahd the 73-80 fenders with vertical turn signal. In 80 or 81 electric choke.

I have a 78 C-10 that came off the assembly line in March 1978 and it did not have the gas doors or the bladed fuses. I have dual tanks with the screw on gas caps showing and the glass type fuses. I believe the gas doors were in the very late 78 model year switch over to the 79 model year. My truck also has no Cats either. :D

You both would be correct on the gas door. It "officially" started on '79 for the pickups, but it started in '78 on the blazer/burbs. As for Cats, I had a '75 that had them. Cats were determined mainly by the GVWR of the Truck.

Other diffs:
73-74 had a center latch on the grille and also hd a unique grille that can no longer be had aftermarket.

73-80 wiper arms were "covered", as 81-87(91) were exposed.

73 was the only year that DIDN'T have drip rails.

73-79 frames had solid frame crossmembers, 80-87 had "lightened" frame crossmembers with holes in them.

73-80 vent window assemblies were "longer" (went to the top of the door frame) 81-87(91) were short.

73-76 no power, 77-up power.

Now I'm curious. My 1980 has outside grill release, as in, under the hood. I know the higher trim levels for that year and earlier years had it inside, but did it go inside for all trim levels in 81?

Yes, I forgot about that one... 1980 it was optional, 1981 up standard.

Oh yeah, '1980 was the first year for the locking vent window.

EDIT Someone posted it and apparently deleted the post, but I didn't say that the inside hood release was availible as an option starting in 1977.

So far everyone has said 78-79 for the gas doors, but I own a 76 that has dual tanks with gas doors on either side and not the screw on caps in the fenders. Was my grandfathers before that and he bought it factory brand new.

Maybe you grandfather had his truck bed replaced with one with gas doors or maybe your truck is not really a 76?

Neither of those are true. I have also met about 3 others on this board who had pre-78/79 pickups with gas doors.

Re: main differences between 73-79, 81-87
 

When did GM start putting the hood release in the cabs? I got donor 76 doors, will the door panels from a 78 fit those doors?

Re: main differences between 73-79, 81-87
 

76 had short door panels, 77 had tall
1980 was round headlight unless chrome grille/halogen headlight option was ordered (which yielded square headlights) I believe std. on Silverado Sierra Classic
on big 3/4 and 1 ton V-8, heat choke until 84, electric in 85-up

R/V designations started in 1987 for all square body
Never known through confirmed VIN or ownership...There were square body SRW std. cab pickups available for 1988 model year. The GM parts book confirms as there is a listing for frame rails as 1988 V309(03), would have been available with carb. or FI.

Unless I'm mistaken, all M/T C/K/R/V including new body style were 10 Spline input to trans.
32 spline output to any aluminum transfer case.
10 spline output through 1984 on NP205 1 ton
32 spline output 85-91 on NP205 1 ton

Re: main differences between 73-79, 81-87
 

It was optional in the late 70's/1980, standard in 1981

Re: main differences between 73-79, 81-87
 

No CUCV truck had drip rails

Heavy GVW 3/4 ton and 1 ton had solid crossmembers for entire production run of C/K/R/V
I believe that is part of the reason for larger door panels in 1977. The lower rear portion of the door panel covers the power lock mounting screws.

Re: main differences between 73-79, 81-87
 

Rebuilt trucks...

Original trucks...

We had a 1978 K2500 GMC, round fuel cap, original paint truck.

We had a 1979 Suburban, bought in 1983 from original owner with original paint, square fuel door.

I had a 1977 GMC C1500 in 1984, round fuel cap.

Re: main differences between 73-79, 81-87
 

All GM 4x4's were produced from the factory with transfer case syncronizers and Automatic hubs and GM's promotion was "shift on the fly" as follows:

81-84 K1/K2
82-84 K3

In 1985/1986 either manual or automatic hubs were available. Automatics were available on K/V 1,2 through 1991. K30 could not get automatics after 1986.

Re: main differences between 73-79, 81-87
 

Lots of wiring differences but can be grouped together.

73-75
76-77
78-83
84 was column mounted wipers
fuse box changed in 85 or 86

73-early 76 tailgates will not fit late 76-up beds unless you cut the jamb for the alignment pins that were on the top of the tailgate, a 72-back style carry over.

One tons were very different from 73-74

73 C30 had Delco Morraine vacuum brakes with 13x2.5 rear drums, no front frame reinforcement struts

74 C30 had Bendix JB8 brakes with hydroboost and 13x3.5 rear drums.

84 and up K/V trucks have a brace rivetted on the RH end of the engine crossmember, where they otherwise all cracked.

85 was the first year of chassis braces under the rear cab crossmember on std.cab. Many 85's got a LH only, later years got them on both sides.

87-89 one ton gas trucks could be had with either TBI or H5D Emission carbureted, except in California.

Some early 73-74's had mechanical cable dual tank switching, others up through 1980 had single pin solenoid valve, 81 up had multipin Pollack.
1980 back had tank switching with a solenoid valve but sending unit swapped at switch. If your solenoid failed and you switched your tank, it would still read fuel level of tank that it's not feeding from!

Many tank sending unit and harness changes through the years on both gas and diesel.

Re: main differences between 73-79, 81-87
 

1981 and newer K/V that were factory equipped with manual hubs will specify option code X6W in glove box.