To respond on this subject please read the entore series first. It will explain I think much better than I do at first. I did not think that I needed too but it just evolved that way. I am sorry if there was not enough stated up front! That is why I posted the HAMB membership spot wher you could see some of what I do and more info on me so that you will understand the level of commitment that I saw was needed from some of the CF's answers. ALL were and are appreciated and WILL be READ! I can assure you. I am not on the computer all of the time and that is why I do not respond quickly! Sorry about this.
Original statement:
We are having a problem with a C-4 Corvette differential and on another one a wheel problem. The Corvettes are a '86 and an '87. Wheels were brought in off of a '92 and did not fit well on the front. Offset was different! (on the car!). What wheels from a later corvette will fit and work properly? He is wanting an 17-18" tire on his car.

On the car that was brought into us with a left side rear upright broken from hitting a curb! We had several C-4 rear ends in stock so we pulled one apart and installed it onto this Corvette. Now one side wheel sticks out of the fender well and the other side seems to be in the correct position. Wheels are off of an '86. The frame does not appear to be bent! The rear mount up looks ok too. ????????????????? Either post here or call 417-300-XXXX. Thanks
Sorry, I got Spammers calling!!!!!!!!!!!!! From somewhere I put out info. (Last 4 digits 5990)

Autoworld Corporation
Joe

 

The offsets are different.. on the 80's vs 91. You need wheel spacers on your older C4 or aftermarket rims for the looks but with the correct backspace on your 86 / 87

 

[QUOTE=Joe Geisler;1581884913]We are having a problem with a C-4 Corvette differential and on another one a wheel problem. The Corvettes are a '86 and an '87. Wheels were brought in off of a '92 and did not fit well on the front. Offset was different! (on the car!). What wheels from a later corvette will fit and work properly? He is wanting an 17-18" tire on his car.

On the car that was brought into us with a left side rear upright broken from hitting a curb! We had several C-4 rear ends in stock so we pulled one apart and installed it onto this Corvette. Now one side wheel sticks out of the fender well and the other side seems to be in the correct position. Wheels are off of an '86. The frame does not appear to be bent! YOU NEED to look at the batwing mounting ears...they bent to one side or the other in many cases without ever bending the frame rails. Its the ears that move not the rails. The rear mount up looks ok too. ????????????????? Either post here or call 417-300-5990. Thanks



Thats unfortunate...

now you have to remove all that stuff you installed if its off a different gen C4 donor and go find the CORRECT yr rear end. They are DIFFERENT.

The suspensions changed to move the hub in or out. Thats why wheel offsets changed.

You MUST use 84-87 OR 88-91(96?) but not a mix of both.
BTW..
the offset is 18mm OR 3/4"

Use 90+ sawblades and a 3/4" spacer/adaptor in the front and a 1" in the rear. You CAN go 1" all around. Use adaptor/spacers NOT spacer plates. A pair cost around $60 on sale.

You can use 88-89 salad shooter 17's...but they're not that attractive...some polished sawblades do nothing but enhance the look of the car...

 

If you had "several" in stock you certainly should have seen the difference when you disassembled the one in stock for the car you were repairing. The car you were repairing should have had shoes on the rear for a parking brake, your choice it seems "from stock" was that of a later that does NOT use shoes. If you didn't notice or see the differences my first guess is that the "installer" is over his head here!

If you installed like for like (a visual inspection should do) then you have problems in other areas. The aluminum cover/support for the rear is broken/damaged or the differential itself is broken at the pinion mount on the c-beam and the entire rear is damaged (frequently happens). If there were damage to the mounts (@ frame rails) the opposite side of the damage should be set outboard of a desired location in the wheel-house.

Check the casting numbers on the upright (knuckle) you removed against the casting numbers on the one you attempted to use to replace it, they likely don't match. Take a look at the suspensions again and I'd say it should be obvious now that there are substantial differences of the rear rotors!

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The '92 wheel you've got if mounted on the repaired side of the rear might confirm what you've done. If the '92MY wheel fits in the wheel-house you've done just what I've mentioned you likely did!

 

When I was tagged broadside by a hostile toyota many yrs ago, the majority of the impact was absorbed by the rear wheel...BIG PROBLEM--->

if the wheel is forced to move inward, so is the batwing...AND the C-beam..AND the trans housing...AND the rear struts & links.

The 1/4" ding in the wheel bead came along with a broken trans housing, bent struts, and bent batwing mounts. A serious PITA to fix...

Whatever that batwing does, is transmitted to the trans/engine since they are linked solid by the C-beam. Even IF there is not a broken case of some sort, a bent drive shaft is almost assured. So things just don;t move well sideways...Easy enough to fix with the FSM dimensions chart and a frame machine...

 

Installer "Over his head"!!! In this instance it's the first issue that needs dealt with. If there's little or no physical damage to anything other than the suspension knuckle/components and they made a "poor" choice from their "in stock" parts I've explained pretty much on how to recover! Until he responds (I doubt) no one will ever know!

We don't know if knuckle to knuckle with differential was replaced or as I guessed just a single side suspension assembly was the attempt!

 

The problem with these cars is they are too low to get a creeper underneath.
If the installer could roll from side to side with the rear wheels off, he would see the difference.
This mismatch comes from someone thinking that they are "all the same", and not paying attention.

Imagine taking your car to Autoworld professionals and having their mechanics going to an enthusiast forum to get the cars fixed right...........

Reinforces what some people said about taking your car to a dealer.

These cars ran from 84-96, and they are specialty cars. No other older GM car is like a corvette from that era.

Nowdays, factories incorporate aluminum suspension parts to save weight.
Another corvette trend utilized by "follower" engineers.

 

These are what you need to fit 88-96 wheels with 56mm offset as compared to the 38mm offset of the 84-87.
You may be able to get some cheaper elsewhere?

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

 

You need wheel spacers on your older C4 or aftermarket rims for the looks but with the correct backspace on your 86 / 87

 

I am not ignoring you guys... and THANKS for the responses!!! I am not on my computer much as I am presently working on building a paint room (from scratch) and also a sandblast room for our inside blasting Get tired of rain and trying to SWEEP up all of the blow around!!!
I do not normally work on Corvettes any more so BARE with me!!! Most of the stuff I did was from 1958 to 1978 when I stopped my Corvette work. So if it is made after 1975 I do not know that much about those years. 54 thur 76 I know! (I never ever worked on a 53!)
I also am not able to look at those 2 Corvettes at this time as they are covered up and YES I will be back on them in the near future. I DO appreciate the help!
Yes, we did install the uprights and I am sure that this is the problem. The ears broke and the wheel shaft were all that appeared damaged. Most of the rears I have in stock are apart. I use them in other car construction. To see that go to HAMB (I am autoworldcorp2000) there are some of my past corvettes and the OTHER projects using the Corvette suspension components. I buy them at the swap meets when the prices are right. Most come from N.Y. and Fla. The vettes that are being worked on are shown there too I think. The Yellow Corvette is one of those RARE C-5 appearing ones that were built as a special project and I will need to know about it and what it was/ is this winter when I can take the time to look it over again. I will reply to each of you soon and again thank you for your responses. I have not been around the C-4's much. I have owned 3 so far and not done anything with them other than trade them off as so far I haven't found the one I like. They are not like the 63-67 nor the 68 thru 76 that I was use to from the bare frame up. (see the HAMB photos).

 

Difference is only from the upright out; all inboard components are the same, 84 - 96
In any case if he installed the wrong upright ,notwithstanding the visual brake differences as already noted by Dave,
he would not be able to re-install the shock as the mounting angle is different ; early vs late
Early angles in to a bracket on the frame while late shock is vertical into bottom of the the frame

 

Mr admaril,
Thanks for the reply on our C-4 wheel problem. SO there IS a difference in the uprights?

 

What in the heck is a saw blade? and a salad shooter???
How to tell the difference between the early and the late upright or do you have the P/N's. Mine are all in piles so it is hard to tell the difference apart. I had the original upright and looked closely but could not tell much difference. In the one I chose. It was hard to tell any difference with the wheels off when I did do the change. One would think that it would be simple... just sit them both down and see which is taller! Did not work that way as I looked! This car is one of the ones that were built to look like the old C-5!!!
Complete body kit. Doesn't look like a kit nor an add on kit!!!! I have looked. Photo shown in my album on CF. This car is yellow like a few others I have seen in Florida. Has the rear spoiler on it too. a fella from the Corvette salvage who delivered our 6 speed trans for it told me that he believes that this Corvette is a RARE BIRD!
ME... ??????? !
Don't have the foggyist! I just know that the rear upright I used is incorrect or else something else is off!!! Being the car was a roll over you'd think it was the rear is driven over! I have been under and all over this car and cannot see anything damaged nor broken. This car was owned by a local principal and has moved on so I cannot get any info from him. The car is what it is. It hit a curb on ice and folded the left side rear wheel under the car breaking the ears off of the upright. Then it tumbled down an imbankment once over. The aluminum housing does seem damaged nor is the carrier assy. broken as someone all ready suggested. The parallel bars were bent too but straightened nicely in our press. Lengths checked out also. I have installed only to roll it around an old set of 86 wheels for right now. The right side wheel sicks out about 3/4 to 1" from the car and the left side that I replaced sets where an 86-87 should it seems!!!
??????????????????
Leading me to start this thread. See the photo of this car and get back to me. I am not on the computer everyday as I am busy building onto our shop. I am building from scratch our paint room and the sand or media blasting room at this time so cars are not a priority at present. But none the less will be in the future and that is why I am seeking information. There are some shop building photos there too but I am a long way from getting back into any cars at this time.
Thanks
PS I HATE being called a JUNIOR member!!! I am one of the OLD CORVETTE crowd and have built corvettes from a BARE frame! See photos. Again none of my trophy winners do I have any FINISHED photos of any more. I did not know that we would have a forum back then!!!! Also 2 divorces many moves and I sold out my old Florida Fiber-Fab business in 1981. I quit corvettes then too it is all explained on the HAMB see my albums if you care to. I am autoworldcorp2000 on the HAMB. You can see more of what I do. I only say this as some made sly remarks as to my level of knowledge about what I am doing on the CF here. You can read it here I am sure. That I am sure is only because they do NOT KNOW me. Thank you again.
Joe

 

there were no 'rare' C4's built to look like C5's from the factory, its a kit, if its the wreck thats under the tarp, un-tarp it , take closer pictures of it and the parts you're trying to repair, you've had excellent advice from these members. if you had pictures of the parts you're trying to interchange, 99.9 % of them would be able to tell you weather they will work or not. This is an excellent crew. They will even be able to identify the maker of your 'kit'. hope this helps

 

If you only have bare items , then the early version ( on the left ) is shorter than the late
and the bolt hole for the lower shock mount is at a angle , not parallel with the ground





The late version shown above on right has the cast alum spacer attached that has the mounts for the brake caliper
( with park brake provision)

The early upright uses a backing plate with drum brake shoes on it for the park brake inside the rotor

 

Hi some base corvettes have 8 1/2 inch rims on front and 9 1/2 inch rims rear, check that you don't have on of each on each side
Z51 will have 9 1/2 inch front and rear.

Some early c4s can have a slight diff/bat wing offset that i have noticed the drivers side rear sitting out maybe 1/4 to half inch difference.

Hope it helps you find the problem

 

It does, and I thank you. I am NOT a know it all. I believe I have said that if you read some of the remarks sent to me on hear you'd understand why I said what I said! you'll find that I am a professional in my trade too. Maybe not on many peoples mind but I have been at this stuff a long long time. I hope I am respected and when I talk members will help out. Credit will always given to those who in a like manor are professional. Many times on Blogs people love to give comments who are on their computer all day. They have NEVER ever taken apart their engines (on their own) let alone their total suspensions. Those people LOVE to give comments and advice it seems. When you do the cars I do then you'll understand. Being TOTALLY respectful here! To you and others but I guess I have to learn to tell the difference. That takes time! I then thru those peoples comments will learn who to put onto my friends list. I asked everyone to check out my HAMB site member albums because I took the time to try to organise them there. I usually cannot take the time to do this as I usually do this in the Winter during being snowed in or such. The information is there on all of the different makes and vintage work I do. I for many years was a college instructor teaching many trades to students... 27.5 years. No one knows me yet on CF and that is not FUN! I just can't jump in and be a Senior member like I wish. At 67 I also care not to wait and somehow sometime be accepted. The time it takes trying to respond and do this stuff takes time away from my work and somebodies car. also not many will ever READ what I write anyway as it is in files that no one ever pulls up forcing me to explain over and over again. That is what will drive people away who are busy.
Hey thanks for the response. I took those photos 3 years ago. I do not yet take a bunch of photos of my work unless the customer wants and pays for me top do that. Also I have just started finding old photos and downloading them onto this computer via flash drives and labeling so that they are retrievable. The only photos that were ever taken of my FINISHED cars was at the car shows where they sell a copy to anyone at the middle of that show. some are on those little key chain viewers and are not download able. The ONLY other completed photos were done by the Auto Trader photographers who came to get the check and the write up. I was there and knew the original start up of the Auto Trader. He started it from his garage at his house in Clearwater Fla. My Florida Fiber-Fab shop was in Ruskin Florida just up from Frankland Manufacturing who built those Quick-Change differentials!!! In fact he and his son Jamie hired several of my students that I taught. I was searching for information here on the subject of the current need on these C-4's and am still in need of the info on the Yellow Car it is not a kit. IT was not made by Chevrolet I am sure but am still wondering about that car. (Before I cut it up and send it to the crusher if it isn't of value. I don't have time to play with something of no value. It will be stripped and parts sold on Ebay if it is of no value other than a RAGGED-OUT C-4 as their value seems in the dirt compared to other years of Corvettes. This one is mine (to sell) and it was brought to me to strip and use what parts I could. It had already been stripped by the last owner and all of the parts sold off. there is no sterring col., seats, dash, console, radiator, engine, trans, headlites, nor hood top.

 

Thank you Vetteoz!!! This is what I need. I used the old upright and one I had in the storage barn to compare. I did have other years that do not look similar to what came off of the car. You can definitely SEE that difference!! I believe I would have definitely NOTICED that! I think!! ????? I may have not! As I thought that all of the C-4's were same! My mistake and I will look for that!!!
These Are what i needed.
The other is to ID that car and try to figure out what has been done to it. I was told by the E bay selling Vette guys in Ark. and another Vette guy in Florida when I described that car at the Webster swap meet, I attend every year, not to destroy it as it is (he believed a series was built of {200?} he thought rare car). I told him I was going to sell off the parts on the E. He asked a few questions and told me what I told you. Yes, there is a kit manufacturer who makes the kit. I've seen it on line a couple of years ago! But there is NO seam-lines on the quarters nor doors!!!!!!!!!!!!!! So that means that they would have HAD to replace the whole door skins and quarters in total!! Most kit car kits don't do this ALTHOUGH today there are really good (fantastic) repo kits using the C-2 bird cage and making the IMSA race versions of the original 3 C-2 racers and also a good 57 without all of the metal supports and brackets used on the origionals. Also a 54, and a 60 I believe (Yadda- yadda). Today you guys (if you have lots of money) are much luckier than we were in the old days when I was into Corvettes. Back then we had to block up a missing front on a fender with plywood bulkheads(same way I learned to make those Balsawood airplanes as a kid), cover it with chicken wire, cover that with paper or LIFE Magazine covers ( they used clay in the printing that stayed with the car after the forms removal)( the clay print not the paper!)! You wet that all down with a hose and off it came but you could still read the cover in the glass patch!), Scotchtaped together. ( after everything was feathe-edge ground of course!) mix up the resin catalize it and use 1-1/2 oz matt. Make sure to keep it green in color. Brown was over catalized and would vibrational crack!!! That always changed with the weather. Then after you removed the armature (buck) you STILL had to grind the back side and glass it at the seam backside! Check your old Corvette shop manuals and you'll see it shown. Funny I had been doing just that for several year before those shop manuals came out!!!! I learned it from a boat repare shop that I went to work at while in high school in the late 50's. Boats had to be right or they'd crack and sink. we have rocks and bolders here in Mo. in our lakes! It had to FLEX in just crossing someone's wake!! I first fixed my boat that I bought with a hole in it and it held up beautifully. Only way a kid could get a cheap speedboat! The motor cost MORE than I had in the boat! Then people started bringing me Corvettes to do. It was not easy back then I can assure you! The Life Mag cover trick...( You dared NOT to tell anyone that! As it would simplify the process)! That was my edge I learned by accident! Normal newspaper, when used, would soak up the resin and had to be GROUND from the patch after cure out. The mag cover I used came right off without the mess!! So research showed me why... the clay print! Off I went to the magazine recirculation piles ripping off those covers!! So that became the winning ticket for me and helped launch me into the man to see in Springfield, Mo. 1958-60. Another learned advantage was the use of Surran Wrap. I had trouble getting the glass to stick overhead. It WAS REALLY messy back then!!!! My Mom came to the rescue!! "Buster, Try using this stuff to mix it up on and see if it will hold it up there". It WORKED!!!! No mess I could smooth it out!!! Gets rid of the excess resin! Comes off easily after curing out. Leaves a shinny surface!!! I used that method a lot! Again you TOLD NO ONE!!! That was my edge! Later on in the 70's it was shown in the GM Shop Manuals on fiberglass repair. I was teaching at the time and not happy about it being out there for anyone to see but that's life! I have found that knowledge comes out in 3's or better in the WHOLE world. There isn't any ONE person who gets the REAL credit for almost any invention nor new process in this world. I guess that was why I was good at teaching for so many years in Fla. You'd have to ask my students and NOT hear that from ME! That is based upon student awards and successes not my yadda!