Car Completely Locking Up in Reverse
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Car Completely Locking Up in Reverse
Got a 1979 C3 with a four speed manual box and a positraction rear end. Rear end was grumbling for a while so I replaced the wheel bearings and a few bushes, put back on the road all seemed good for about 100 miles, then the grumbling and shuddering of the whole car at very low speeds, slipping the clutch a bit in town traffic conditions started.
Yesterday I was out and about, wanted to reverse into a parking space and the whole back of the car lifted as though, either the hand brake was on or I had hit a high kerb, neither of which had happened. I managed to drive about 40 or so miles back home without issue but then when trying to reverse at home the very same thing happened again, locked up solid so today I removed the diff, my thinking was that as there was some slack in the drive yolks something may have got damaged in the diff and it was locking up the crown wheel.
Having now removed the diff and opened it up I can't see anything that stands out as incorrect, I haven't fully cleaned it yet so will look deeper when it's cleaned up but to make the car come to an abrupt halt I was expecting to see some obvious carnage.
Anyone got any ideas what might be causing this?
Yesterday I was out and about, wanted to reverse into a parking space and the whole back of the car lifted as though, either the hand brake was on or I had hit a high kerb, neither of which had happened. I managed to drive about 40 or so miles back home without issue but then when trying to reverse at home the very same thing happened again, locked up solid so today I removed the diff, my thinking was that as there was some slack in the drive yolks something may have got damaged in the diff and it was locking up the crown wheel.
Having now removed the diff and opened it up I can't see anything that stands out as incorrect, I haven't fully cleaned it yet so will look deeper when it's cleaned up but to make the car come to an abrupt halt I was expecting to see some obvious carnage.
Anyone got any ideas what might be causing this?
Tech Contributor
Joined: Aug 1999
Posts: 15,154
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From: Connecticut, USA
If you have the diff out, can you spin the pinion in either direction without binding? If it's in the diff look for a broken ring gear bolt or cross shaft bolt that would lock up the diff. Should be obvious once you check it.
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Hi thanks for the response. Got the diff out no bolts missing all in place, no debris in the diff or housing, all oil drained out. Pinion turns easy by hand in either direction, no binding at all.
I do have a huge amount of play in the side yolks which i knew about when I did the wheel bearings.
I'm this far in so I may as well remove everything and do a rebuild, will have to do a google on how to and what parts I need.
My next worry is if it isn't the diff then it can really only be the gearbox and I'm leaning towards removing that as well while I have the car off the road.
I do have a huge amount of play in the side yolks which i knew about when I did the wheel bearings.
I'm this far in so I may as well remove everything and do a rebuild, will have to do a google on how to and what parts I need.
My next worry is if it isn't the diff then it can really only be the gearbox and I'm leaning towards removing that as well while I have the car off the road.
Melting Slicks
Joined: May 2021
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From: Fleming Island, FL
From what you are describing, (rear end lifting in reverse) something in the trailing arm assembly has gone amok. My guess would be something with the parking brake. I can't see how a problem with the differential is going to cause the car to lift its rear end in reverse.
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I've seen cars lock up in reverse, manual transmission.
but that's generally being in 2 gears at the same time. Which will stall the engine when you let out the clutch.
So I agree, I don't think the problem is in the transmission.
I would be looking at wheel bearings/parking brake issues.
but that's generally being in 2 gears at the same time. Which will stall the engine when you let out the clutch.
So I agree, I don't think the problem is in the transmission.
I would be looking at wheel bearings/parking brake issues.
Tech Contributor
Joined: Aug 1999
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From: Connecticut, USA
79 would have a BW super T-10 4 speed, some had Saginaw which were weak.
Since you have the diff out you can check it and the outer axles individually. If they are free, your issue is forward as you're thinking.
The outer axle should rotate- not free wheel- without any binding, forward or reverse. You should not have any rocking pressing on the rotors at 3 & 9, there should be now endplay if you grab a wheel stud and push/pull on it.
The 79 diff's had bad axles, clutches, and ring gear bolts. The quality or replacement axles today, new or rebuilt, needs to be understood and checked no matter where you buy them. There are issues with all of them. I had a 50% rejection rate with some, others are bad design, and some may not be the same steel GM used. The diff should be built to your application. If that is just a driver, no high power, no abuse, a stock-built diff will work. A more detailed one will work better.
If you're a handy guy and have access to measuring tools, possibly machinery- depending on how you want to build it, and good hand tools you can do it at home.
Since you have the diff out you can check it and the outer axles individually. If they are free, your issue is forward as you're thinking.
The outer axle should rotate- not free wheel- without any binding, forward or reverse. You should not have any rocking pressing on the rotors at 3 & 9, there should be now endplay if you grab a wheel stud and push/pull on it.
The 79 diff's had bad axles, clutches, and ring gear bolts. The quality or replacement axles today, new or rebuilt, needs to be understood and checked no matter where you buy them. There are issues with all of them. I had a 50% rejection rate with some, others are bad design, and some may not be the same steel GM used. The diff should be built to your application. If that is just a driver, no high power, no abuse, a stock-built diff will work. A more detailed one will work better.
If you're a handy guy and have access to measuring tools, possibly machinery- depending on how you want to build it, and good hand tools you can do it at home.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,032
Likes: 4,387
From: Marlton NJ
I too was almost positive you had a broken gear tooth or a loose ring gear bolt...but...
"Rear end lifting" clue...
I do not see how that could be transmission or diff.
The wheel bearings just got worked on. A problem is frequently in the last are a that was worked on. So check the parking brake parts.
You should have both half-shafts off already since the diff is out.
Pull the wheel and rotors and see how the new wheel bearings spin. Both directions. Look at the parking brake stuff. Spin it with rotors on and rotors off.
I agree something binding in there could use the trailing arm as leverage and try to jack up the rear of car.
"Rear end lifting" clue...
I do not see how that could be transmission or diff.
The wheel bearings just got worked on. A problem is frequently in the last are a that was worked on. So check the parking brake parts.
You should have both half-shafts off already since the diff is out.
Pull the wheel and rotors and see how the new wheel bearings spin. Both directions. Look at the parking brake stuff. Spin it with rotors on and rotors off.
I agree something binding in there could use the trailing arm as leverage and try to jack up the rear of car.
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Le Mans Master
Joined: Jan 2001
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stilltrying
I also thought you had gotten that lousy gearshift into 2 gears at the same time...... happened to me lotsa times. Annoying.
I also thought you had gotten that lousy gearshift into 2 gears at the same time...... happened to me lotsa times. Annoying.
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From what you are describing, (rear end lifting in reverse) something in the trailing arm assembly has gone amok. My guess would be something with the parking brake. I can't see how a problem with the differential is going to cause the car to lift its rear end in reverse.
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I've seen cars lock up in reverse, manual transmission.
but that's generally being in 2 gears at the same time. Which will stall the engine when you let out the clutch.
So I agree, I don't think the problem is in the transmission.
I would be looking at wheel bearings/parking brake issues.
but that's generally being in 2 gears at the same time. Which will stall the engine when you let out the clutch.
So I agree, I don't think the problem is in the transmission.
I would be looking at wheel bearings/parking brake issues.
All new bearings and bushes along with brake shoes etc. and as said to a previous reply both side would have to be doing exactly the same thing at exactly the same time plus I doubt that the parking brake would stop the vehicle completely dead but would "give" as in not grab instantly. When this happens it is instant dead stop. Having said that I will remove the calipers and look at the parking brake system just to check as the wheels are already off.
The gear change is a little "loose" and has been for a very long time, maybe it's got worse and I just haven't noticed, hadn't thought it could be engaging two gears at the same time. Whatever is going on it is locking up both sides of the car at the very same time as both side raise not just one side.
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I'm sure the linkages need what ever bushes replacing so will take a look.
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79 would have a BW super T-10 4 speed, some had Saginaw which were weak.
Since you have the diff out you can check it and the outer axles individually. If they are free, your issue is forward as you're thinking.
The outer axle should rotate- not free wheel- without any binding, forward or reverse. You should not have any rocking pressing on the rotors at 3 & 9, there should be now endplay if you grab a wheel stud and push/pull on it.
The 79 diff's had bad axles, clutches, and ring gear bolts. The quality or replacement axles today, new or rebuilt, needs to be understood and checked no matter where you buy them. There are issues with all of them. I had a 50% rejection rate with some, others are bad design, and some may not be the same steel GM used. The diff should be built to your application. If that is just a driver, no high power, no abuse, a stock-built diff will work. A more detailed one will work better.
If you're a handy guy and have access to measuring tools, possibly machinery- depending on how you want to build it, and good hand tools you can do it at home.
Since you have the diff out you can check it and the outer axles individually. If they are free, your issue is forward as you're thinking.
The outer axle should rotate- not free wheel- without any binding, forward or reverse. You should not have any rocking pressing on the rotors at 3 & 9, there should be now endplay if you grab a wheel stud and push/pull on it.
The 79 diff's had bad axles, clutches, and ring gear bolts. The quality or replacement axles today, new or rebuilt, needs to be understood and checked no matter where you buy them. There are issues with all of them. I had a 50% rejection rate with some, others are bad design, and some may not be the same steel GM used. The diff should be built to your application. If that is just a driver, no high power, no abuse, a stock-built diff will work. A more detailed one will work better.
If you're a handy guy and have access to measuring tools, possibly machinery- depending on how you want to build it, and good hand tools you can do it at home.
The diff needs a rebuild as there is a load of movement in and out, I knew this when I did the trailing arms but thought I would get the summer driving done and do a rebuild during the winter, however, now I have completely removed the diff now is the time to do it.
The outer axles do not free wheel I have to use some pressure but they are free in both directions as is the pinion, a quick look and I can see that this has been out of the car before as there is a load of blue sealant on the rear cover, however, this would have been more than twenty years ago, prior to my ownership.
I will take some photo's and post up incase anyone can see an obvious issue. I know the side yokes need work that is for sure.
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I too was almost positive you had a broken gear tooth or a loose ring gear bolt...but...
"Rear end lifting" clue...
I do not see how that could be transmission or diff.
The wheel bearings just got worked on. A problem is frequently in the last are a that was worked on. So check the parking brake parts.
You should have both half-shafts off already since the diff is out.
Pull the wheel and rotors and see how the new wheel bearings spin. Both directions. Look at the parking brake stuff. Spin it with rotors on and rotors off.
I agree something binding in there could use the trailing arm as leverage and try to jack up the rear of car.
"Rear end lifting" clue...
I do not see how that could be transmission or diff.
The wheel bearings just got worked on. A problem is frequently in the last are a that was worked on. So check the parking brake parts.
You should have both half-shafts off already since the diff is out.
Pull the wheel and rotors and see how the new wheel bearings spin. Both directions. Look at the parking brake stuff. Spin it with rotors on and rotors off.
I agree something binding in there could use the trailing arm as leverage and try to jack up the rear of car.
When this happens the car completely locks up dead which I doubt the braking system is capable of and it's both sides at exactly the same time, with the force this stops the car I would expect to see contact patches inside the drum area or on the hub so not discounting anything yet but will let you know what I find inside.
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stilltrying
I also thought you had gotten that lousy gearshift into 2 gears at the same time...... happened to me lotsa times. Annoying.
I also thought you had gotten that lousy gearshift into 2 gears at the same time...... happened to me lotsa times. Annoying.
Someone mentioned that the engine would die as well but to be honest this has only happened very recently when I was first trying to reverse park in a space so I was slipping the clutch at the time then the car raised up and I thought I had hit a kerb so obviously dipped the clutch instantly, if I had not done so then it very well may have killed the engine. When I got home I went to reverse but was waiting for it to happen, which it did, so again dipped the clutch instantly so I have no idea if it would have killed the engine. It's too late now to check as it is all apart.
Le Mans Master
Joined: Jan 2006
Posts: 6,504
Likes: 139
From: Butler Pa
I doubt that the parking brake would stop the vehicle completely dead but would "give" as in not grab instantly. When this happens it is instant dead stop. Having said that I will remove the calipers and look at the parking brake system just to check as the wheels are already off.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,032
Likes: 4,387
From: Marlton NJ
Clue... complete stop within less than a foot of travel.
Well that clue sounds like the trans is in two gears at once, reverse plus another. It is kinda common. That would be a shifter issue.
You already ruled out a broken diff gear tooth. So now you have two things left to check, shifter and park brake.
You'll get there.
Interpreting people's clues can get very difficult and even entertaining at times. But we are here to help.
Does anyone remember the joke about the mechanic who could not duplicate the older lady's stalling problem?
She said: "I told you, it only happens when I get ice cream!"
LOL
Well that clue sounds like the trans is in two gears at once, reverse plus another. It is kinda common. That would be a shifter issue.
You already ruled out a broken diff gear tooth. So now you have two things left to check, shifter and park brake.
You'll get there.
Interpreting people's clues can get very difficult and even entertaining at times. But we are here to help.
Does anyone remember the joke about the mechanic who could not duplicate the older lady's stalling problem?
She said: "I told you, it only happens when I get ice cream!"
LOL
Last edited by leigh1322; Jun 2, 2025 at 10:16 AM.
Advanced
Joined: Sep 2008
Posts: 59
Likes: 12
From: London Ontario, Canada
Got a 1979 C3 with a four speed manual box and a positraction rear end. Rear end was grumbling for a while so I replaced the wheel bearings and a few bushes, put back on the road all seemed good for about 100 miles, then the grumbling and shuddering of the whole car at very low speeds, slipping the clutch a bit in town traffic conditions started.
Yesterday I was out and about, wanted to reverse into a parking space and the whole back of the car lifted as though, either the hand brake was on or I had hit a high kerb, neither of which had happened. I managed to drive about 40 or so miles back home without issue but then when trying to reverse at home the very same thing happened again, locked up solid so today I removed the diff, my thinking was that as there was some slack in the drive yolks something may have got damaged in the diff and it was locking up the crown wheel.
Having now removed the diff and opened it up I can't see anything that stands out as incorrect, I haven't fully cleaned it yet so will look deeper when it's cleaned up but to make the car come to an abrupt halt I was expecting to see some obvious carnage.
Anyone got any ideas what might be causing this?
Yesterday I was out and about, wanted to reverse into a parking space and the whole back of the car lifted as though, either the hand brake was on or I had hit a high kerb, neither of which had happened. I managed to drive about 40 or so miles back home without issue but then when trying to reverse at home the very same thing happened again, locked up solid so today I removed the diff, my thinking was that as there was some slack in the drive yolks something may have got damaged in the diff and it was locking up the crown wheel.
Having now removed the diff and opened it up I can't see anything that stands out as incorrect, I haven't fully cleaned it yet so will look deeper when it's cleaned up but to make the car come to an abrupt halt I was expecting to see some obvious carnage.
Anyone got any ideas what might be causing this?
Le Mans Master
Joined: Jan 2001
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stilltrying
well..... it's easy enough to check if you already have it up in the air. If not, then jack the driver side of the car up, jack-stand it, and crawl under there and ensure the linkage is not in 2 gears at the same time.
And, YES, it tends to happen when you go into reverse, come out of it, and slap into 1st and then your car doesn't move..... if you're LUCKY then you're able to wiggle it back into Neutral and out of both gears..... then select the gear you wish and it moves.
If such is the case, and pending the adjustment/tightening/refurbishing of the shifter just be real gentle and no quick shifting......
well..... it's easy enough to check if you already have it up in the air. If not, then jack the driver side of the car up, jack-stand it, and crawl under there and ensure the linkage is not in 2 gears at the same time.
And, YES, it tends to happen when you go into reverse, come out of it, and slap into 1st and then your car doesn't move..... if you're LUCKY then you're able to wiggle it back into Neutral and out of both gears..... then select the gear you wish and it moves.
If such is the case, and pending the adjustment/tightening/refurbishing of the shifter just be real gentle and no quick shifting......
Hi thanks, this was not something I had thought about but if it is relatively common than I need to check all the linkages as a first step. When it happens it is a dead stop and raise of the rear end within lest than a foot of travel.
Someone mentioned that the engine would die as well but to be honest this has only happened very recently when I was first trying to reverse park in a space so I was slipping the clutch at the time then the car raised up and I thought I had hit a kerb so obviously dipped the clutch instantly, if I had not done so then it very well may have killed the engine. When I got home I went to reverse but was waiting for it to happen, which it did, so again dipped the clutch instantly so I have no idea if it would have killed the engine. It's too late now to check as it is all apart.
Someone mentioned that the engine would die as well but to be honest this has only happened very recently when I was first trying to reverse park in a space so I was slipping the clutch at the time then the car raised up and I thought I had hit a kerb so obviously dipped the clutch instantly, if I had not done so then it very well may have killed the engine. When I got home I went to reverse but was waiting for it to happen, which it did, so again dipped the clutch instantly so I have no idea if it would have killed the engine. It's too late now to check as it is all apart.
Le Mans Master
Joined: Jan 2001
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oh.... and another pointer.....
I have learned to come here and ask before I get carried away fixing things because I assumed something ...... lots of folks here with lots of experience. They've straightened me out lots of times.
I am assuming things from your initial description....but I *think* you put it into Reverse, then went to drive forward and it wouldn't move...... I reckon that you then wiggled the shifter around until you were to get going again? Not sure? So I'm guessing..... that's what would happen to mine..... EXCEPT I was never lucky enough to wiggle it out of lockup and had to crawl under to put the shifter back into neutral.
I have learned to come here and ask before I get carried away fixing things because I assumed something ...... lots of folks here with lots of experience. They've straightened me out lots of times.
I am assuming things from your initial description....but I *think* you put it into Reverse, then went to drive forward and it wouldn't move...... I reckon that you then wiggled the shifter around until you were to get going again? Not sure? So I'm guessing..... that's what would happen to mine..... EXCEPT I was never lucky enough to wiggle it out of lockup and had to crawl under to put the shifter back into neutral.