I will be rechecking the park brake but I would be amazed if both sides are doing exactly the same thing only in reverse but I’m not discounting anything at the moment but will let everyone know what it is or isn’t as I find out.

 

yet another double post sorry

 

double post sorry

 

I’m going to recheck the parking brake as that is the easiest first, then move on to the shifter set up.

I do appreciate everyone’s help as over here there are not a lot of vettes, even less with a manual box and less again where the actual owners work on their own car. I do have the assembly manual as well as a couple of workshop manuals but real people’s experience is by far the best way to learn.

I will take some photos and post them up to see if they help in anyway. I now wish I had taken a video of the car trying to go in reverse but by the time I got home it was gone midnight and then in the morning I just set to and got the diff out.

 

Thanks, I have already checked the joints and non are in anyway binding or show any signs of wear, all moving freely all greased up no dry bits.

 

This is the first place I come to when anything goes wrong as everyone was really helpful and sorted out my carb issue a while back.

The exact opposite to your issue is happening, I can drive for miles forwards and on this particular occasion had driven about 30 miles in stop start traffic with speed limited to 20 MPH YES 20 MPH for the majority of my journey (Went to London for a cruise and all the inner area is now a blanket 20, the car hated it as did I), anyway got to a place to park, put the car in reverse and within a foot or so the car stopped dead and the back started to jack up like I was trying to ride up a kerb, put it into first gear and it would clunk then drive away forwards, put it back in reverse and the same issue stopped dead, eventually drove home and when trying to go in reverse after the journey it did exactly the same thing.

I will take some photos and post up of the diff and the parking brakes, I know I have to rebuild the diff as it has way too much play in the side yokes so now its out that is going to get done.

 

If the tranny is locked up in 2 gears, then no power would go to the diff. No driveshaft rotation. Sounds to me like something is locking up at the hubs causing the whole trailing arm to move.

 

Thats what happen to my car. The driver side shoe spring broke, causing the shoes to jamb while backing up. it connects the top of the parking brake shoes.

 

Thanks for your input, I see the logic and as said I will be removing the calipers and disc's to check, just need some spare time to do so.

 

Thanks, I'm going to check as soon as time allows and will let people know what I find.

 

Unfortunately I have not had any spare time to dismantle the rear brakes as yet but did take some photos of the diff, no broken or loose bolts, teeth all fine, posi works but there is a lot of play in the side yolks, can’t see any hair line cracks either.





The stamped numbers

Inner ends of the yolks

 

Your axle stubs (yokes) appear to be worn flat.
At least your c-clips are still there, but I see no chamfer on the edge.

The two on the right in the pic below are that way, and they even wore down past the c-clip groove.
My two on the left only have minor wear, even after 90k miles. They measure almost as new, and have a wide 45 degree chamfer at the edge of the splines.
The like new measurement from top of c-clip groove to end of axle stub, is .185-.190"

The quality of the heat treating got worse as the years went by. Mine are 71 axles. The bad ones on the right are late 70's.

 

Great advice given.
OP
i have your car exactly.
here are the threads and help and advice i got including fixes.

Axle end play
https://www.corvetteforum.com/forums...ay-advice.html

e brake coming apart
https://www.corvetteforum.com/forums...82-please.html

 

The pictures tell a story.
The diff has been apart before. The axles are shot, but axle endplay comes from more than one area in the diff.
The gears look like 1973- 355's. It appears the RG bolts are not from 1979 as well.
The diff is nothing beyond a stock level build at best not what I would use but it may be ok.
Cracks can form at any opening typically. Some are hidden under the RG at times.
There is no apparent damage from locking up in reverse. If the pinion rotates without issue, your problem looks to be elsewhere. Whether to use the diff in that condition is up to you. Replacing the axles is straight forward, what you get will make a difference- but just changing out the axles will most likely not bring them where they should be. I just fit rebuilt axles today. I should not have to refit parts I bought but these were not ready to use. There are several options for axles today, depending on the usage, some are good and some are not.
Good luck

 

Thank you all for your replies.

I was fairly sure that the diff had been apart before due to the amount of sealant that was used to seal the cover on, I’ve had this vehicle for the best part of twenty years and never done anything with the rear end except fitting new wheel bearings, some bushes, shocks and over time the two calipers, so that probably tells you more about my style of driving, not a drag car, think I’ve only ever done two burnouts (showing off), but do give it the beans when driving. The gearing has always been something I was not happy with in that I really don’t need first gear and it runs out of steam at the top end around 100+MPH, so years ago I sourced a set of gears that should give me better top end and cruising than the current set up but I haven’t checked the ratio yet. Bear in mind that over here gas is more than double what you pay over there, hence wanting better cruising speeds.

The side yolks have no chamfer on them and I did put a dial gauge on to see what the side movement was and got .080” on the passenger side and .095” on the drivers side.

I will check out the links you have given me and see what to do from there, obviously side yolks are required but who or where to get them from is going to be the next question as second hand spares over here are also very few.

 

It will be interesting to see what you end up with for axles. I inspect every axle I buy, some have a 50% rejection rate. The set I pulled out of the box yesterday, one fit the spider easy the other didn't. I had to dress it to fit. These were from the 50% that passed my inspection. I have some of the new axles here too. They are most likely made in China. They are cast hardened not thru hardened, that is how they were sold. They will work in a driver but I would never use or sell them for a car with power or abuse. For most of my builds I use GM axles that are in my spec, that I have had thru hardened and cryo treated. The next level up are 30 spline axles but those require new spiders and machining the posi case. Given your application, those are not required.

What brand of gears do you have and what is the ratio. I would confirm what you have now, a simple rotation check will confirm if they are indeed 355's. Going to lower numerical gear will bring down the highway cruise RPM as the expense of start up but that depends on the Tq of the engine and trans used. Present gearing is all imported today, mostly from China. If you have 355's then the next lower would be 336, then 308. There used to be a 273 as well. You can use the common online gear calculators to compare RPM with each ratio but don't expect a huge increase in mileage. That requires a OD trans and FI which add a lot to the car budget.

Good luck

 

I've played with the gear calculators online and from 3.55 to 3.36 drops your 4th gear rpm approx. 190-200 rpm. Same going from 3.36 to 3.08.

 

Once again thanks for the replies, the axles I will have to source from the states I’m sure, we do have three corvette specialists over here but they are not cheap and often it’s cheaper and in some cases quicker to get from the states.

As for reducing the overall revs, I will go check the ratio that is in it now but from memory the gears I bought are 3.08:1

 

The existing gear ratio is 3.55:1 the new second hand gear ratio is 3.08:1

I have time this weekend to look at the brakes so will post results as and when.

 

You keep saying "from the states". Why don't you publish where you live? You have no profile.