K5 Tailgate Window Adjustment

[79vette]

I have an '86 K5 with a manual tailgate window. Back in April the window bound up due to a rusted through sash and the pot metal "clutch" that couples the handle to the regulator broke.

I used that as an excuse to go through it, and cleaned and greased the regulator, replaced the rollers, replaced the flocking in the side channels, replaced the felt seals on the top of the tailgate, replaced the broken handle and clutch, replaced the sash, and replaced all the rubber seals on the shell. Spent >$600 on parts for a $2000 truck, and assumed it would be good to go...

The window never worked right with the new felt pieces, and was really tight to roll up and down. I figured the felts would wear in and take a set over time, but they didnt. Now 6 months later, my new handle broke again...

I have the regulator completely removed, and the glass still will not go up and down freely. It binds from about 30% raised to 80% raised, and will travel the first and last bit smoothly. I'm out of ideas, and about ready to go spend another $1500 on a soft top, pickup tailgate and paint... Are there any adjustments I might have missed, or a procedure for getting the side channels lined up or something? Maybe my tailgate frame is bent somehow? Any suggestions are welcome.

In 10 years of working on old trucks, this is by far the most aggravating single problem I've encountered. Diesel swap, multiple auto to manual conversions, turbo install, lots of rust repairs, transmission rebuilds, nothing comes close.


EDIT: I messed around with this again for several hours tonight. Took the glass out, checked the track alignment, cleaned and greased everything, and no change. Is there anything that can be used to lubricate the felt seals? Silicone, graphite, etc?

Tailgate frame seems to be straight. The glass is curved however, so it does not match the shape of the straight tailgate?


The window seems to be binding against the inner felt strip along the outside 4" or so of glass on each side. I cannot see any possible way to adjust this other than modifying the tailgate frame. It does not seem possible to bend it (too stiff in the out of plane direction), so it would be cutting/welding to open up the clearance between these felts...



Between the red lines (5.5" above the bottom of the glass to 17" up) the glass binds. Outside that it moves freely. The curvature of the glass seems more exaggerated in the center section, not sure if that matters...

[SilverMiner]

79vette -

I encountered a similar problem when I refurbished the tailgate on my 1980 Suburban a couple years ago. K5 and Burb tailgates aren't identical, and my tailgate is electric rather than manual, but perhaps this will help. Going purely on memory I believe the problem was resolved by adjusting the sashes at the lowest point by leaving the attaching screw slightly loose and then running the window partway up to the point where it begins to bind. Then I tweaked the window into what felt like a better position, secured the sash screws. Repeat as necessary.

As I said, this is from memory, but I'm fairly confident that proper adjustment of the sashes will solve your binding problems. Hopefully others will chime in with more specific suggestions in case I'm remembering wrong.

[79vette]

Thanks for your reply


Last night I removed the glass from the sash (metal piece that connects to the glass and bolts to the regulator arms), and removed both the sash and the regulator from the truck. I also loosened all the bolts in the guide tracks on the sides so both tracks were free to move.

In that configuration, just sliding the glass in and out by itself it still seems to bind between the felt strips at the top of the tailgate. I'll try to adjust the tracks again tonight, but it seems like with them complete loose any binding would be minimized since the glass could just move into whatever position puts the least pressure on it at the seals.

Is there any chance there is a year split for glass/tailgates? I always thought they were the same from 73-91, but my glass is pretty clearly curved side to side and the tailgate opening is very straight. This seems to be what is causing the binding (middle of the window is jamming hard into the outer seal, and the edges are jamming hard into the inner seal)

[SilverMiner]

Originally Posted by 79vette

....

Is there any chance there is a year split for glass/tailgates? I always thought they were the same from 73-91, but my glass is pretty clearly curved side to side and the tailgate opening is very straight. This seems to be what is causing the binding (middle of the window is jamming hard into the outer seal, and the edges are jamming hard into the inner seal)

You've got me wondering now. I happen to have both a 1978 Jimmy as well as the 1980 Suburban so I just went out and put a 24" straightedge on the rear glass of both of them. I wish I had something longer (my big level is too long with the windows up), but as best as I can tell both are straight rather than curved. The channels are certainly straight.

Like you, I would have bet money that the cheap accountants at GM would never have bothered to change the glass from 73 to 91, although I do know the door glass got thinner at some point over that time. But at the same time I can't think of anything other than a K5 that your glass could have come from... I've never measured Wagoneer, Cherokee or Bronco glass but would be utterly shocked if they were even close. I'm still amazed they bothered to construct the K5 and Suburban tailgates differently.

Could you take a photo with your big level sitting on the glass and measure the difference in the center? I'm curious now to know just how much curvature you're talking about.

[79vette]

with the level across the inside bottom edge of the glass touching at the edges, there is 0.25" of space between the straight edge and the center of the window.


I dont necessarily know if it was the "correct" fix, but I took the glass and felt seals out again tonight and used a prybar to increase the size of the opening at the top of the gate by ~1/8". Its an not noticeable to the eye, and the only way to tell is to measure the opening with a scale or a caliper.

Now the glass rolls up and down smoothly like how I remember my old K5 was, with gentle pressure on the crank handle. The felt seals now just touch the glass when its fully rolled up instead of "clamping" it, and time will tell if the inside of the tailgate will be water and dust proof or not. Maybe I'll have to come back to this in a year when the seals start to wear and try to bend the gate back, who knows. Hopefully not, since these K5 tailgates are getting hard to find anymore...