Captainpegs07

I just bought a Curt C4 hitch. It has the hardware to fit the early and late C4's. I see the frame rails and when I put the hitch up to it, it looks like the brackets that hold the rear bumper on is in the way. I have attached a pic. The hitch is about 1" away from the frame because of the bracket.

Captainpegs07

Here is a pic of just the bracket:

Captainpegs07

Am I suppose to cut that flange off or what?!

TerryOlson

If trimming the flange off will allow the hitch to mount I'd do it. Judging from what can be seen in the photos it looks like that's how it's designed to work, but I understand your hesitation to do so.

WVZR-1

Why wouldn't you just take some better snapshots, make note of the year (which you haven't done here but "hinted" maybe early) and contact Curt? Their instructions mention no cutting/removing of structure so I'd think I'd ask them. You've never mentioned the part # you bought but judging from your snapshot it appears to be fabricated like a C4 hitch from them.

They've got toll free numbers all over he country so I just don't understand "NOT asking them"!

Joe, John and Jim say "cut it"! Still doesn't work then what?

Silver96ce

Maybe the hitch was incorrectly welded together. Maybe it is the wrong hitch. Maybe a piece goes between the hitch mounting point and the frame. Who knows? - the company that sold it to you. Take your photo and send it to them and ask them.

emptnest

I am planning the same installation on a 1993.

Please post an update to tell how you resolve this question.

Thanks.

c4cruiser

Some years ago, I bought a Reese hitch for my '87. There were different part numbers for the hitch based on the year of the car. IIRC, it was 84-90, and 91-96. I didn't have to cut anything.

I would contact Curt to see if there are different part numbers or if they made a change in the design. If you bought from a 3rd party, maybe the hitch got swapped into a different box.

Captainpegs07

I wanted to follow up. The hitch was the correct one. The flange must be used in the mfg process as it serves no purpose on the car and needs to get cut off. The hitch has 4 bolt holes to mount it to the car, two on each side. the back holes, towards the rear of the car, were drilled 3/4 inch too far forward which put them in a spot which is impossible to get the bolts all the way in and nuts on them. I drilled two holes in the subframe before realizing this error in the hitch. I ended up drilling a NEW hole in the hitch in the correct spot. It's tight and there's little wiggle room for error. It would have been FAR better if Curt Manufacturing just left it for the owner to drill his/her own rear holes.

The instructions also called to torque the bolts to 100 ft lbs. I set my wrench at 75 ft lbs and found that even this reduction was too much and I was compressing the subframe. I expect this cause some fracturing/cracking but without a bore scope I won't know to what extent.

All in all I'm pretty pissed off with the Curt Mfg hitch for the C4. Bad holes caused me to swiss cheese my frame and ridiculous torque specs caused me to compress and damage the sub frame. It works for my 300lb boat and trailer - about 20lb tongue weight - but I do regularly check for frame cracking .

c4cruiser

Were there some rectangular spacers provided in the kit? My hitch had four 1"x1-1/2" "bolt plates" (a good 1/8" thick) that were used on the nut side of the bolts.

These were for spreading the torque load over the frame rails. I didn't see any sort of problem when I tightened the bolts on my Reese hitch. The torque values for the bolts were 75 ft-lbs for 1/2" bolts and 35 ft-lbs for 3/8" bolts.

The two long bolts installed with the threads pointing up and the small bolts at the back of the hitch were installed with threads pointing down.

Captainpegs07

Yes, I used the supplied backing plates. The issue was location of the two bolt holes towards the rear and the torque spec.

Mishawaka

I used to be in the towing business years ago, I don't ever recall installing a hitch on a Corvette (we probably would have fabricated it) but it wasn't uncommon to trim sections of a urethane bumper or a uni-body frame. You may want to use some thread locking compound on the nuts and bolts then torque. I would just keep an eye on everything especially the tongue weight.

GQ-ROD

Captainpeg07 could you post pics of the completed installation, i'm planning on installing the same hitch and would greatly appreciate seeing the holes you drilled to locate the mounting bolts.

Thanks!

Captainpegs07

I'm pulling the car out of the shed this Saturday. I will try to get the pics posted Sunday.

GQ-ROD

Thanks, looking forward to it !

antfarmer2

My vette and hummer do there own jobs could never think of doing that

Captainpegs07

Just remedying a factory oversight. It only pulls the light boat or a bike rack.

GQ-ROD

I agree, it helps to be able to use a bike rack and add some utility to the vette.

I can already see what you mean about the hitch mounting hole nearest the rear bumper being too far back, you were right.

I've already cut off the brackets and ground down the frame where the brackets mounted.

There's very little space up top near the tank and frame.

Captainpegs07

[QUOTE=GQ-ROD;1589210715]

I can already see what you mean about the hitch mounting hole nearest the rear bumper being too far back, you were right. QUOTE]

The holes in mine were too far forward. I had to drill new ones in the hitch farther back towards the rear of the car. Either way, I used two floor jacks to hold the thing up so I could take my time and get it all lined up and make double sure I understood what I was doing.

GQ-ROD

[QUOTE=Captainpegs07;1589211049]Thanks for the advice. It really helped a lot !

I just finished installing the curt hitch, best deal was on ebay 200 bucks, free shipping and free ball mount ( no ball though ).

It was a BEAR to say the least.

In my case i decided to eliminate the spare tire carrier.

It was easier for me to do this and line up the mounting holes in the center of the sub frame, than to drill the extra holes in the hitch because i noticed this hitch is waaaay out of whack in terms of how it lines up with the sub frame. It's not perfect by any means.

The gap on top of the sub frame is SO narrow, about an inch if you are lucky between the rear sub frame to the gas tank that to try to line up a new hole upside down at an angle was impossible for me.

Also on the top of the sub frame it's not level, it has a piece that looks like a lap joint welded there.

So getting the nut to rest flush to the top of the frame is impossible without fabrication of a plate flat on top and lap joint on the bottom similar to an L shape which i quickly made with my flux core welder. BUT with no space to even test fit, that was a bear test fitting to get it right.

Used a harbor freight step drill bit, which worked fine but working upside down has to be the worst way to work on a car ever, i also bought a cobalt 1/2 x 6 " long drill bit.

Cut both brackets off that you mentioned in your post, with a sawzall with bi-metal blade and used a thin 4 1/2" depressed center cut off wheel on my dewalt grinder to clean the old welds.

I can attest to the fact that the maximum torque to place on the 1/2 " bolts is no more than 55 foot pounds in ten pound increments, at 60 or more it will slightly deform the sub frame. I checked with a straight edge and when i got 1/16th of space i stopped and that was at 60 foot pounds !

And on the smaller end nuts i used 40 foot pounds each, however i reversed the smaller plate from what was shown in the instructions to have the space to mount them.

Honestly this hitch mounting is pure crud !

It would have been easier to drill a hole in the middle of the sub frame then fish wire a steel bracket behind and into the sub frame as well as shorter mounting bolts as is done on later vettes. Would have been done in 30 mins if this were the case, otherwise it literally took me all day to do this.

BUT it's done!, it's safe for very light loads and will serve the purpose of carrying a bike.

Thanks again for your help and posting this thread it really helped me avoid a big mistake.