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Many of you are familiar with my LS swapped C4.
Anyhow thought this thing was bullet proof, but I was wrong. Last night on the road I suffered a pretty dramatic u-joint/halfshaft failure. Sounded like a bomb went off behind my seat and through parts everywhere plus cut the rear brake hose.
Then I had a 4 hour wait on the side of the road for a tow truck. I will say although it was a very long wait the tow guy was very good and very careful and even helped me put the back end up on jackstands in the garage.
Amazingly AND THANKFULLY, the paint and body are ok. But the underside is total carnage.
Hole in the storage compartment behind the driver's seat. Somehow missed the ABS module:
The batwing was actually cut clean in half, missed the fuel line, thank God!
My Dana 44 with 3.73 gears is toast.
Sadly my Z51 spring and the spring brackets were also damaged.
at this point the destroyed parts are:
-Dana 44
-batwing cover (for Dana 44)
-driver's side halfshaft and u-joint
-rear Z51 leaf spring and spring brackets
-fiberglass damage to driver's side storage cubby
-driver's side rear tire
-driver's side wheel well liner
-driver's side braided rear brake hose.
So the question is where do we do from here?
Option 1:
rebuild like before with forged u-joints and hope for the best.
Can I even find a replacement Dana 44?
Option 2:
Rebuild it stronger so it is unlikely to break again.
-Hammerhead rear differential
-u-joint/axle shafts ??? What are the upgrade options?
my LS proabblu puts out a little over 500hp but who know maybe I'll upgrade in the future for more power, me know your opinions are what would you do?
Has the 'Hammerhead' actually been released with the correct short-axle modifications etc?
I don't recall what ratio you were running in the D44 but the fastest reassembly would be a purchase of another D44 if there is one near you.
street shop Inc. Has released a hammerhead diff that bolts right up to c4 corvette, so they say on their website.
I have 3.73 ratio in my Dana 44, it is even possible the gears might be salvageable. However, I can see the gear set through a hole in the side of the Dana 44 so it's not a sure thing they weren't damaged.
I'm just trying to decide, put it back together like it was and hope for the best or try to make to stronger?
However, if there isn't much way to upgrade the u-joints or half shafts which are the weakest link then I'm not sure an upgraded diff has any value.
Anybody know what some of the C4 corvettes in the optima challenge did for rear end/half shafts???
street shop Inc. Has released a hammerhead diff that bolts right up to c4 corvette, so they say on their website.
But they've never displayed or mentioned what's used for 'short-axles' and a half-shaft. I was told at one time to maybe expect a 'constant velocity' affair likely. I asked SSI several times for confirmations and never heard a word. SSI has generally been known for certainly their 'ATTITUDE'!!! Use the SSI web-order and you'll see different differential options. Each of those I'd think would require a very different 'short-axle'?
What happened to the left side 'short-axle'?
I have NOS housing and rear cover, I believe I've a 3.73 NEW gear and a NEW Dana differential also. I do have NOS 'short-axles' also.
Here's a 'Hammerhead' that seems to have yokes attached to 'something' used as a splined 'short-axle' . This arrangement means you've still got U-joints. Did you twist and bust a half-shaft or was it a confirmed U-joint failure? Your snapshot seems to maybe indicate a 'end-yoke' failure on the half-shaft.
Ok guys I've done some more 'post mortem' analysis and in my case what appears has happened is one of the u-joint strap bolts backed out a little, which must have allowed some play and I guess it snapped. Also I put the car in neutral and the rear end rotates freely, no strange sounds etc... so although the case got broken I don't believe it was the cause.
So that informs me of the cause. Now I just have to decide is this the time to do upgrades, or is it good enough like it was if that bolt didn't back out.
I will say at my current power level I would think it was good enough like it was...I know once people start using drag radials and 600+hp it sounds like that's usually when parts are broken. Not 500ish hp on street tires.
Ok guys I'm done some more 'post mortem' analysis and in my case what appears has happened is one of the u-joint strap bolts backed out a little, which must have allowed some play and I guess it snapped.
So that informs me of the cause. Now I just have to decide is this the time to do upgrades, or is it good enough like it was if that bolt didn't back out.
I will say at my current power level I would think it was good enough like it was...I know once people start using drag radials and 600+hp it sounds like that's usually when parts are broken. Not 500ish hp on street tires.
my opinion, repair it as it was. loctite ujoint strap bolts. im going out to inspect mine!!!!!
my opinion, repair it as it was. loctite ujoint strap bolts. im going out to inspect mine!!!!!
Yes, this is a painful lesson for me, but for the rest of the C4 community inspect those u-joints and check the bolts are tight, you don't want this to happen to you!
I had only inspected the u-joints once a year and last time was in Sept, I will check mine regularly now.
So this has me thinking about a debate I read here years ago about steel half shafts.
Back when I had my driveshaft made by Action Machine for my 4L80e swap the head machinist there (Bob Guzman) told me that in the past he made steel 4130 half shafts with forged steel welded on yokes for C4's. Told me at that time it would be under $600 for both of them with solid forged Spicer U joints included. I kind of thought that he was just trying to up sell me. But I wonder if steel half shafts and upgraded U joints would have helped you guys.
He can also make heavier aluminum half shafts. But he told me they are so short that the difference in weight between steel vs aluminum would be negligible in a street car. I ended up going with a 3" steel driveshaft with forged 1350 yokes from him. I was more than impressed with the quality and the price was unbeatable. If the general consensus here is that the steel half shafts with solid U joints could stop this kind of damage I might just do this over the winter.
...I know once people start using drag radials and 600+hp it sounds like that's usually when parts are broken. Not 500ish hp on street tires.
(I've got both...)
In general, U joint straps like that can stretch over time. In my former life, I built off road trucks, and there, even with small engines, we were much harder on driveline parts, compared to hot rods. It was common for us to carry spare driveshafts, joints, etc on every trip because failure rates were so high. (For example, my 4 cyl Toyota had 200:1 multiplication due to aftermarket low gears + 2nd low range box).
Anyway, U joint failures were common, and the typical start was the straps holding them down. You can tighten the bolts all you want, but the strap itself stretches over time and needs to be replaced. For off road trucks, we would use U-bolt style straps instead, which were OEM on most earlier vehicle. Drag guys look into fancier caps/girdles to replace the straps, but I don't know if either option is possible to fit the range of motion needed on the half shafts for a C4.
So this has me thinking about a debate I read here years ago about steel half shafts.
Back when I had my driveshaft made by Action Machine for my 4L80e swap the head machinist there (Bob Guzman) told me that in the past he made steel 4130 half shafts with forged steel welded on yokes for C4's. Told me at that time it would be under $600 for both of them with solid forged Spicer U joints included. I kind of thought that he was just trying to up sell me. But I wonder if steel half shafts and upgraded U joints would have helped you guys.
He can also make heavier aluminum half shafts. But he told me they are so short that the difference in weight between steel vs aluminum would be negligible in a street car. I ended up going with a 3" steel driveshaft with forged 1350 yokes from him. I was more than impressed with the quality and the price was unbeatable. If the general consensus here is that the steel half shafts with solid U joints could stop this kind of damage I might just do this over the winter.
Thoughts?
Depends on what failed. If the U joints or straps on the diff yoke failed, the half shaft isn't a factor in the equation. Going to steel makes sense if you are either twisting the tube, or elongating the aluminum yokes at the end, allowing the U joint to break or come free.
On the flip side, failure at speed with a steel shaft might do even more damage, if its was rotating and tomahawking through the car (looks like what happened to yours?)
I can't remember, is yours a stick or auto? Autos tend to be easier on the shock loading. Had you ever put in new joints and/or inspected the yokes?
Last edited by haggar1850; Jul 8, 2022 at 10:09 AM.
The early ZR-1 had steel half shafts. My 0278 does. But they went back to aluminum. Are aluminum ZR-1 half shafts different than regular car half-shafts? I have no idea, and didn't look it up, but if the ZR-1 are stronger, they may be 'findable' at less expense than custom shafts.
I don't know for sure but I would imagine that a steel ZR1 half shaft would not only have Corvette tax but also ZR1 tax. So it might be cheaper to have a set made. Most good shops will make a forged steel shaft with U joints installed for around $300-$350 each. No idea what the factory ZR1's go for.
My car is manual. T56 MAGNUM, with a twin disc clutch and LS engine, 3.73 rear gears. I wasn't launching the car, this happened on the shift into 3rd gear.
Yes, nothing old or crusty under the car, which made this such a surprise.
So now that I'm done crying it's time to plan out the repair.
it sounds like the first piece I should look into are upgraded u-joint caps
My car is manual. T56 MAGNUM, with a twin disc clutch and LS engine, 3.73 rear gears. I wasn't launching the car, this happened on the shift into 3rd gear.
Yes, nothing old or crusty under the car, which made this such a surprise.
So now that I'm done crying it's time to plan out the repair.
it sounds like the first piece I should look into are upgraded u-joint caps
There is very likely not enough clearance to use that package with the 1350 joints on the rear. I wouldn't rush to buy unless someone verifies that they will clear/work on the rear of a C4.
Dramatic u-joint/halfshaft failure.
it's time to plan out the repair.
