[aitch]

I've got a mid rise topper, with the small curvature at the base of the front end (designed for the 2nd gen S10 cab profile). There is a (normal) gap of about 1 3/8" between it and the cab. I grew weary of having compounded obscured rear vision directly behind me when it rained. With the topper on, there are 3 glass surfaces behind the driver position, instead of just the one at the back of the cab. Both the cab and topper have the slider window feature. It seemed that a seal between the topper and the cab would resolve the problem. I wasn't impressed with the inflatable "one size (doesn't) fit all" plastic topper boots available for this application, and it's also less expensive.

I used 2 pieces of (6') black, closed cell neoprene foam (for 3/4" pipe, outdoor grade, approx. 2 1/4" O.D. (Armacell 3/4 in. x 6 ft. Rubber Self-Seal Pipe Wrap Insulation HST07812 - The Home Depot). I used 3M black weather strip adhesive at the butt joint seam, and then cut the piece to proper length. Following the profile of the cab & topper, the weather strip is compression fit between the cab and the topper, from top of bed rail to opposing top of bed rail. As the cab & bed are independent of each other, there is the chance of finish chafing on one or both of them due to movement, so I will keep an eye on that, although I suspect it may be minimal, and a long term issue rather than a short term issue. From a moderate distance and a passing glance, the seal is barely visible.

The seal has been exposed to the high pressure spray and blow dry cycles at the (touchless) car wash along with highway speed trips, and is holding up well so far. I pop thru the carwash on occasion, primarily for the underbody 'wash', to help keep road grime & (winter) salts minimized. The cab rear and topper front windows stay dry and clear. And with a coat of Rain X on the rear glass of the topper, it's easier to monitor tailgaters, runaway concrete trucks, and any other approaching hazards/ idiots behind me. And, yes, I regularly use both rear view mirrors as well.

 

[oldeerslayer]

Sounds like a good fix.
I though back in the day there was a open cell seal you could buy. IIRC it was self stick on the cap side.

 

[aitch]

Sounds like a good fix.
I though back in the day there was a open cell seal you could buy. IIRC it was self stick on the cap side.

I think I came across something like that, but I dismissed it, as (at least some of) the open cell foams can retain water, which can freeze (& expand). Anyway, this seemed like it was worth a try, plus, it didn't involve unclamping, repositioning, and re-clamping the cap to apply an adhesive seal.

 

[hit_4_show]

Interesting. I definitely consider decreased rear view mirror visibility an irritating cost of using a cap.

 

[aitch]

Interesting. I definitely consider decreased rear view mirror visibility an irritating cost of using a cap.

With the foam seal in place, the rear cab window & the front topper window remain clear, clean, & dry, so only the topper rear window gets weather exposure (& decreased clarity in the rain). A rear wiper feature for toppers would be a great option (like those on the Blazer lift gates).