1980 Rear end strength
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
There is no real hard and fast data available. Some people have the carrier give up before the case, while others have the case crack. It just depends.
If you are going to upgrade the engine significantly then yeah, updating the rear end would be advisable. New machined bearing caps are one mod that is done to help out. Stub axles with hardened ends should be done regardless of power levels. Use the halfshafts from the 81 4spd or any 82 since they are slightly bigger.
The old schoolers will just tell you to mod the car to accept the iron diff mated to the aluminum cover.
If you are going to upgrade the engine significantly then yeah, updating the rear end would be advisable. New machined bearing caps are one mod that is done to help out. Stub axles with hardened ends should be done regardless of power levels. Use the halfshafts from the 81 4spd or any 82 since they are slightly bigger.
The old schoolers will just tell you to mod the car to accept the iron diff mated to the aluminum cover.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Haven't done it myself, but there are a few guys here who have installed 10-bolt hog heads into batwings with only a little work. Too bad there apparently isn't enough material to accept a converted 12-bolt IRS diff (have one in my shark), but IMCO a well built 10-bolt would still be a sound upgrade. My $.02, in old money...
edit - The C3/D44 batwing can be adapted to accept a 12-bolt IRS diff with a spacer/mid-plate to make up for lack of material.
edit - The C3/D44 batwing can be adapted to accept a 12-bolt IRS diff with a spacer/mid-plate to make up for lack of material.
Last edited by TheSkunkWorks; Oct 1, 2011 at 09:51 PM.
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 4,435
Likes: 9
From: Kalamazoo Mi
Haven't done it myself, but there are a few guys here who have installed 10-bolt hog heads into batwings with only a little work. Too bad there apparently isn't enough material to accept a converted 12-bolt IRS diff (have one in my shark), but IMCO a well built 10-bolt would still be a sound upgrade. My $.02, in old money...
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
IIRC Bee Jay and 69427 have both done the 10-bolt / batwing adaptation, so I'll drop them a VM to see if they'll join in since I'm not 100% up on it. Doesn't look that difficult.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Mines stock and has only been cleaned up inside with new C clips installed about 12 years and sees around 550-600 ft/lbs and 600HP every time I take it out.
This is from rolling start, no wheel spin with my foot pushed not to fast to the floor when I hit max torque @ 5000 RPM.
Dana 44 very underrated punkin. Now if I rev it past idle and dump the clutch with slicks, it probably would get scared and break before I let the clutch out
This is from rolling start, no wheel spin with my foot pushed not to fast to the floor when I hit max torque @ 5000 RPM.
Dana 44 very underrated punkin. Now if I rev it past idle and dump the clutch with slicks, it probably would get scared and break before I let the clutch out
Instructor
Joined: Apr 2010
Posts: 233
Likes: 2
From: Sacramento CA
Actually, I'm glad this was asked. I'm curious too!
I'm not sure what the OP's situation is, but here's mine:
I, Currently, have my Diff and Battwing from my 1980 A/T 305 at JAWS Gear & Axle here in Sacramento (there a sponsor on LS1tech. I've used them before and trust there work). The owner called me today with some bad news. My axle stubs have gone south taking out the stock posi unit.
The diff has 84k miles on it and the motor is all stock!!!! That's not a very well built rear diff, IMO! The owner said that the diff really needs hardened stubs to prevent this from happening. Hell, The only reason I took it in was to have new seals installed because it leaks all over the place.
Well, I got a quote of >$1300. That's for hardened stubs, new posi, bearings, seals. The only thing that's worth a damn are the ring and pinion!!!
Seems to me the stock diff isn't worth a poop!
So, for me personally, I'm at a crossroads here. Do I;
Have the work done?
Upgrade any other parts to make it strong?
Or just do a swap over to something stronger?
I've searched on here and found that there are some things you can do to make the Alum diff stronger, but are they worth it?
Just FYI, I do plan a mild LSx swap with a 700R4/4L60E swap at some point, so I'd only like to do this once, LOL.
I'm not sure what the OP's situation is, but here's mine:
I, Currently, have my Diff and Battwing from my 1980 A/T 305 at JAWS Gear & Axle here in Sacramento (there a sponsor on LS1tech. I've used them before and trust there work). The owner called me today with some bad news. My axle stubs have gone south taking out the stock posi unit.
The diff has 84k miles on it and the motor is all stock!!!! That's not a very well built rear diff, IMO! The owner said that the diff really needs hardened stubs to prevent this from happening. Hell, The only reason I took it in was to have new seals installed because it leaks all over the place.
Well, I got a quote of >$1300. That's for hardened stubs, new posi, bearings, seals. The only thing that's worth a damn are the ring and pinion!!!
Seems to me the stock diff isn't worth a poop!
So, for me personally, I'm at a crossroads here. Do I;
Have the work done?
Upgrade any other parts to make it strong?
Or just do a swap over to something stronger?
I've searched on here and found that there are some things you can do to make the Alum diff stronger, but are they worth it?
Just FYI, I do plan a mild LSx swap with a 700R4/4L60E swap at some point, so I'd only like to do this once, LOL.
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Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
You can break one with a stock motor, you can break an iron diff with a stock motor.
I've seen C5-C6 diffs explode at the drag strip more times than I care to wait for the cleanup or close the lane down.
It all depends on how good you or the previous owner were at abusing it. A leaking diff is probably not going to get fixed with seals and gaskets most of the time it'll cost a few buck more.
I've seen C5-C6 diffs explode at the drag strip more times than I care to wait for the cleanup or close the lane down.
It all depends on how good you or the previous owner were at abusing it. A leaking diff is probably not going to get fixed with seals and gaskets most of the time it'll cost a few buck more.
Instructor
Joined: Apr 2010
Posts: 233
Likes: 2
From: Sacramento CA
Actually, I'm glad this was asked. I'm curious too!
I'm not sure what the OP's situation is, but here's mine:
I, Currently, have my Diff and Battwing from my 1980 A/T 305 at JAWS Gear & Axle here in Sacramento (there a sponsor on LS1tech. I've used them before and trust there work). The owner called me today with some bad news. My axle stubs have gone south taking out the stock posi unit.
The diff has 84k miles on it and the motor is all stock!!!! That's not a very well built rear diff, IMO! The owner said that the diff really needs hardened stubs to prevent this from happening. Hell, The only reason I took it in was to have new seals installed because it leaks all over the place.
Well, I got a quote of >$1300. That's for hardened stubs, new posi, bearings, seals. The only thing that's worth a damn are the ring and pinion!!!
Seems to me the stock diff isn't worth a poop!
So, for me personally, I'm at a crossroads here. Do I;
Have the work done?
Upgrade any other parts to make it strong?
Or just do a swap over to something stronger?
I've searched on here and found that there are some things you can do to make the Alum diff stronger, but are they worth it?
Just FYI, I do plan a mild LSx swap with a 700R4/4L60E swap at some point, so I'd only like to do this once, LOL.
I'm not sure what the OP's situation is, but here's mine:
I, Currently, have my Diff and Battwing from my 1980 A/T 305 at JAWS Gear & Axle here in Sacramento (there a sponsor on LS1tech. I've used them before and trust there work). The owner called me today with some bad news. My axle stubs have gone south taking out the stock posi unit.
The diff has 84k miles on it and the motor is all stock!!!! That's not a very well built rear diff, IMO! The owner said that the diff really needs hardened stubs to prevent this from happening. Hell, The only reason I took it in was to have new seals installed because it leaks all over the place.
Well, I got a quote of >$1300. That's for hardened stubs, new posi, bearings, seals. The only thing that's worth a damn are the ring and pinion!!!
Seems to me the stock diff isn't worth a poop!
So, for me personally, I'm at a crossroads here. Do I;
Have the work done?
Upgrade any other parts to make it strong?
Or just do a swap over to something stronger?
I've searched on here and found that there are some things you can do to make the Alum diff stronger, but are they worth it?
Just FYI, I do plan a mild LSx swap with a 700R4/4L60E swap at some point, so I'd only like to do this once, LOL.
Instructor
Joined: Apr 2010
Posts: 233
Likes: 2
From: Sacramento CA
I'd really like to know as well.
I have my rear diff out of my 1980 A/T 305 84k mile in the shop with an estimate of >$1300 to rebuild it!
Apparently, the stubs took out the posi unit. So, it needs a new posi, hardened stubs, then bearings and seals.
So, is the stock alum diff worth even putting money into?
If its not, I'd be willing to put more then that into a stronger diff...if I only have to do this once.
I have my rear diff out of my 1980 A/T 305 84k mile in the shop with an estimate of >$1300 to rebuild it!
Apparently, the stubs took out the posi unit. So, it needs a new posi, hardened stubs, then bearings and seals.
So, is the stock alum diff worth even putting money into?
If its not, I'd be willing to put more then that into a stronger diff...if I only have to do this once.
Last edited by SOMFormula; Sep 29, 2010 at 09:35 PM. Reason: double post
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
If you have an automatic 305 just rebuild it, you will be fine. Someone abused it along the way. Be glad you don't live up here, no one would re and re C3 diff for under a grand and that's without doing any work on it
Instructor
Joined: Apr 2010
Posts: 233
Likes: 2
From: Sacramento CA
My fear is, 10k miles down the road when I put an LSx in it, that I can blow out a $1300 rear. Now THAT will ruin my day.
The car doesn't seem abused. I will say this, the gear oil is the original gear oil from 1980
Also, the car has been sitting for about 4+ years...in the weeds...outside.
Instructor
Joined: Apr 2010
Posts: 233
Likes: 2
From: Sacramento CA
I'm going to go ahead with the rebuild.
But, I was thinking of having one of those steel (or billet) end caps installed while I have the rear diff being rebuilt.
Does anyone know where I can purchase one?
But, I was thinking of having one of those steel (or billet) end caps installed while I have the rear diff being rebuilt.
Does anyone know where I can purchase one?
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
I did the conversion in my car, I did it to be safe, as I did a big block conversion. To do the mod, you need an iron pumpkin, (69-79 are the same I believe, I used a 71), a pinion mounting bracket, strut rods for the pumpkin (they're in a different position on the iron units and therefore are different lengths and are straight as opposed to offset), a strut rod mounting bracket and half shafts and flanges to replace the yokes on the TA spindels. The only real fabrication I had to do was the pinion mount, I had to shorten the tounge a bit to clear the cross memeber. You'll also have to get the drive shaft length changed, the necessary length will depend on the trans you have.
I went from the original 2:72 to a 3:36, which is one of the reasons I went with the swap when I did. It was either this or rebuild my original unit with steel caps and a different gear set to get the ratio I was looking for. This is the closest to a "bolt in" modification I've seen yet. I also added a rear stabilizer bar when I did the conversion. Seemed a good time!!
I went from the original 2:72 to a 3:36, which is one of the reasons I went with the swap when I did. It was either this or rebuild my original unit with steel caps and a different gear set to get the ratio I was looking for. This is the closest to a "bolt in" modification I've seen yet. I also added a rear stabilizer bar when I did the conversion. Seemed a good time!!
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
Bought a used 80 rear diff - didn't want to muck up my original and also I could still drive the car while working on the rear. $250 + shipping.
New stub axles - $160 each.
New rebuild kit - $125 (timken bearings and new seals).
New Ring and Pinion set - 3.55 ratio Yukon gears....no noise thus far. $180.
New clutches from Tom's Diffs. $54.
New pinion cross shaft. $50...didn't fit quite right and needed some work to fit right.
All new Spicer nonserviceable (solid) u-joints (all 6). $120.
Lubes and other misc stuff - $50 or so.
Polished the carrier with a dremel. Removed all the old bearings and cleaned up the case. Later painted and clear coated it. Looks good.
Had rear end setup by ProGear here in San Diego for $170. I already had the clutches in and crossshaft mounted as well. Ring gear was installed as well. Supplied my own setup bearings for the job ($80) but couldn't set the pinion depth correctly so packed it in and paid the pros. Money well spent I think.
So the price you have been quoted isn't that unreasonable since you don't have to do any of the work. My car is rust free so taking it apart was relatively easy.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I did the conversion in my car, I did it to be safe, as I did a big block conversion. To do the mod, you need an iron pumpkin, (69-79 are the same I believe, I used a 71), a pinion mounting bracket, strut rods for the pumpkin (they're in a different position on the iron units and therefore are different lengths and are straight as opposed to offset), a strut rod mounting bracket and half shafts and flanges to replace the yokes on the TA spindels. The only real fabrication I had to do was the pinion mount, I had to shorten the tounge a bit to clear the cross memeber. You'll also have to get the drive shaft length changed, the necessary length will depend on the trans you have.
I went from the original 2:72 to a 3:36, which is one of the reasons I went with the swap when I did. It was either this or rebuild my original unit with steel caps and a different gear set to get the ratio I was looking for. This is the closest to a "bolt in" modification I've seen yet. I also added a rear stabilizer bar when I did the conversion. Seemed a good time!!
I went from the original 2:72 to a 3:36, which is one of the reasons I went with the swap when I did. It was either this or rebuild my original unit with steel caps and a different gear set to get the ratio I was looking for. This is the closest to a "bolt in" modification I've seen yet. I also added a rear stabilizer bar when I did the conversion. Seemed a good time!!
hope it pans out as you can break iron diff too.If you have the talent and fabrication skills then I would say go for it. Many have problems changing spark plugs or starting their cars after the distributor has been out so as you can see unless you can do it all yourself it starts to become out of reach.
I build my own engines and make my own parts etc etc but I can't weld worth a crap and the simple reason is I haven't had enough experience or should I say enough things to weld, I do own a mig welder though. I welded something for my brother once and he dropped it on the floor and the weld broke, haven't done much welding since, especially for him
