Hi guys, I have a 78 and the rear bumper has been missing so I tried to install one from a 79/80 and it wobbles. I don’t have the access panel for the rear strut nuts in the trunk and I’m guessing that’s why it wobbles. Or was there different strut lengths over the years? Do you think the access is under the gas tank? I don’t want to drop it to find out it’s not there. Plus when I removed the original bumper 20 years ago I don’t remember having to drop the tank.


Do t have this access panel

 

I stripped an '80 and I believe the nut is underneath the hatch somewhere, but it's been a while so I can't be absolutely sure.

I would think it's easy enough to trace as the threaded end goes into the rear somewhere...

 

The threaded end of each strut is bolted to a plate inside the rear frame rails. It definitely will wobble without it. My 79 (Nov. 78 mfg. date) has access through the pictured hole under the plate on the floor inside the rear hatch area (inside the car above where the rear frame rails meet the floor). I have never seen one without this access point as it would be impossible to install or service them without a means to get at that bolt. I'm sorry I don't have a better picture as I used part of the space from that opening to mount the rear bar for my roll cage. You can see the plate that bolt goes through from the top view and the view looking into the rear frame rail. If the access point is not there then feel around the sides and bottom of the frame rail forward of where that plate is to see if there was an alternate opening for some strange reason.
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unfortunately, I have a piece of iron over the hole in this photo. The hole and that access panel are right behind that bar.
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Top of opening and attachment plate inside the rear hatch area. Again, I covered the front part of the opening with my roll bar. Sorry it's not a better shot.
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Looking into the rear frame rail from behind the car. You can see the hole that threaded rod bolts into and the two points for the other bolt holes.
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Hope that helps.

 

The original poster has a Savanna car. JDM cars were not required to have 5 MPH bumpers. This was a US requirement and is the reason for the bumper shocks. Japan did not have the same safety requirements and JDM bumpers did not contain the same reinforcement and were attached with simple brackets in place of the bumper shocks.

I have North American cars all built between March of 78 and July of 79. They all have the same access pockets for the nuts at the ends of the bumper shocks in the rear deck floor, as pictured and described above.

I also have a 78 Savanna, built the first month of production. I can confirm that the OP is correct, although it does have the tunnel for a shock to fit in, it does not have an access window from either the rear deck floor or underneath as the JDM cars used a different design of bumpers and method of attachment.

I'm not sure that cutting a window would help either. US cars also have a plate at the far end of the tunnel with a hole. The threaded end of the bumper shock goes through this hole and the nut and jam nut go up against this plate, anchoring the inboard end of the shock. My JDM car does not have that plate either. With the bumper removed, the OP can look down the tunnel with a flash light and see if there is a plate and/or any access to the other end of the tunnel.

 

An illustration from my JDM parts manual. The bumper itself is much lighter than the US version and uses different spec end caps as well.

 

Well, ain't that just a pisser. I did not know that about the JDM cars. See you can teach an old dog new tricks if you hit him with the stick instead of throwing it.

 

Well that small but important piece of information would've been useful from the start lol! I just looked at the username and it says it all!

Good idea to flash some light in the hole to see if it opens up somewhere else. If not, maybe use an endoscope to look inside the hole.

Banzai, how is your rear bumper supported on your '78 Savanna? Post a picture.

 

Originally, it would have been by those 2 small brackets. Unfortunately, when the car came into my hands, it had been worked over by previous owners and neglected for some time. It was re-sprayed in another shade of green and was missing quite a few parts. The original bumper was gone and someone had mounted a US bumper just like the original poster described at the beginning of this thread. Not sure if the US spec bumper was someones attempt at "federalizing" the car or not.

I have no real info on how the car arrived in the states or its history. I suspect it possibly could have been brought back by a service member returning from overseas back in the day. It belonged to the estate of a long time Rotary enthusiast who died in 2019 with a whole building full of various cars and parts he had accumulated over several years.

It's my long term project now, one which I've shoved off to a corner and have only been collecting parts for the last few years while working on other cars. My desire is to completely go through it and bring it back. I probably have 90% of the missing parts and only have one more car ahead of it, to go through first. A Daytona Blue 79 that I acquired a couple years ago and plan on beginning to take apart next month. Once done with that, I'll be in a much better position to think more seriously about the Savanna project. Possibly in 2027 or so?

 

In case the OP is interested, here is a better shot of how a JDM rear bumper is attached. The two brackets bolt up to where the bumper shocks would normally go and attach to the bumper itself in three places. Looks like they are just carriage bolts with round heads on the exterior. The ones on the rear face would be covered by the rubber strip. Wouldn't take much to make a pair and mount them to a US spec bumper.

 

Thank You for the pictures. I will need to look down the tube to see if there is whole to be able to bolt the bumper shock. If not Maybe I can fabricate something. Are you in SD?