Usual disclaimers apply. I know this is an easy job for some (most) of you, but I'm posting:
1.) For all the non-mechanics out there to know they can do it (if I can get this done, anyone can)
2.) Just to show the steps involved for anyone contemplating a similar switch
As usual, if I did something incorrectly, please feel free to post a correction or suggestion- no offense taken! :thumbsup:
The issue:
I had eliminated all the usual suspects (axle bearings, u-joints, clutch, etc.) in trying to resolve a "tunk, tunk" sound from my rear axle, so it was time to bite the bullet and replace the 8" chunk. While I was at it, I figured I would go from my current 3.20 gear to a 3.55.
The parts:
The result:
No more "tunk, tunk!" The old carrier allowed the pinion to wobble a bit- and I'm sure that was the cause of the noise. The back end of the car feels really solid now. The 3.55 is PERFECTION with my inline six and T5 transmission. I've previously owned a '65 C-code automatic (2.80 rear end) and the setup I have now feels a lot crisper off the line. I will never "fear the gear" again, I've had a 2.80 in this car, then a 3.20, and now a 3.55. (I think the next step up is 3.90... hmmm).
I do still have some resonance thrumming at various speeds, which I think I can resolve by tinkering with the pinion angle (since changing the angle changes the thrumming). Update- I was able to virtually eliminate the resonance thrumming by setting the pinion angle back to flat AND by reinstalling my lowering blocks (I believe the blocks help in decreasing the angle of the driveshaft between the trans tail and pinion). I also need to swap the speedo gear out on the T5, because it is reading about 10% fast now. The '85-89 V8 T-5 trans in my car has a 7 tooth speedometer gear, so the correct driven (cable) gear should be the 20 tooth (I had an 18 tooth driven gear with the 3.25).
The process:
1. Lift the back and remove the rear wheels (remember to chock the front wheels). I would recommend getting the car fairly high up, since you'll want to use a small trolley jack to support the chunks as you remove & install.
2. Remove the axles. There's a hole in the mounting plate at the end of the axle- line it up with the four bolts (9/16") on the bearing retaining plate to remove it. Then give the axle a good yank. If it doesn't pop right out, you can turn the drum around, loosely install some lugs, and use the drum as a slide hammer (pictured). As you pull the axle out, support it so it doesn't damage your axle seals. You don't have to remove any of the brake hardware.
3. Disconnect the bolts (1/2") that hold the u-joint to the pinion. Put some tape around the two newly freed u-joint bearings. Otherwise, if the cap pops off, you're likely to have needle bearings all over the place. I just lowered the back end of the driveshaft and moved it to the side.
4. Place an oil catch under the diff, and remove the 10 bolts that hold it on. I left one bolt on the side loose, and then carefully used a chisel to pop loose the seal (actually, I used my big hammer to work the chisel in between the axle housing and chunk... I've been told this can score the housing and cause a leak- so its better to just whack on the side of the pinion housing with a dead blow hammer until it releases from the seal) . Allow the gear oil to drain into your pan.
5. Once the seal is released, the diff will come off. If 60-70 lbs is not heavy for you, fine- otherwise, the diff could be described as heavy. I found it was much easier to remove (you have to slide it straight forward due to the 10 studs it sits on) by using a trolley jack to support some of the weight. Just be aware that when it finally clears the axle housing, gravity will come into effect.
6. Scrape all the old seal off the axle housing. Apply gasket seal (blue or black) to one side of the gasket, and put the sealed side onto the axle housing.
7. Apply gasket seal to the new differential mounting surface and then install on the 10 studs (again, a trolley jack helped me a lot).
8. Reinstall the 10 washers and/or bolts. Not sure what the torque specs are, but I noticed mine weren't super tight when I removed them, so I didn't go nuts making them super tight when I reinstalled.
9. Slide the axles back in (again, being careful not to damage your axle seals). In fact, its a good time to inspect your axle seals, bearings, and the gaskets on your bearing retainer plate. If the bearings spin really easily, they're at the end of their life (there should be smooth resistance as you rotate the bearing around the axle).
10. Reinstall the bearing retainer plates and wheels.
11. Install 2.5-3.0 quarts of gear oil. To get better access, I relocated my jacks to the rear frame rails and let the axle come down with the trolley jack. This gives better access. BTW, there are two possible locations for the fill plug. The early axles had the plug on the back of the axle housing- but no plug on the diff carrier. The later axles were vice versa. This is important to know, because if you have a later axle housing and install an early diff carrier, you'll have no fill plug. The '67+ diff carrier is stronger anyway (and will fit either the early or late axle carriers) so that's the surefire way to go.
Adding the gear oil was actually the hardest step in the process for me! I bought the gallon container, which was a mistake. 85w140 is like molasses at 45 degrees (the temp in my garage), so my siphon tube wouldn't move the stuff. Trying to use a funnel was comical (now, not at the time) and resulted in a bunch of oil all over the garage floor- but none in the diff! Finally, I went and purchased one quart, put that in, then refilled the bottle twice.
12. Reinstall the fill plug.
13. Reinstall the u-joint to the pinion.
14. Get the car out of the air and enjoy.
1.) For all the non-mechanics out there to know they can do it (if I can get this done, anyone can)
2.) Just to show the steps involved for anyone contemplating a similar switch
As usual, if I did something incorrectly, please feel free to post a correction or suggestion- no offense taken! :thumbsup:
The issue:
I had eliminated all the usual suspects (axle bearings, u-joints, clutch, etc.) in trying to resolve a "tunk, tunk" sound from my rear axle, so it was time to bite the bullet and replace the 8" chunk. While I was at it, I figured I would go from my current 3.20 gear to a 3.55.
The parts:
- Rebuilt open 3.55 (with a '67+ case). Built by Terry Todd, who is based in Indiana (812-749-4308, or ttodd21@hotmail.com). Very friendly and knowledgeable person to deal with, and I couldn't be happier- called him Thursday afternoon and the finished product arrived at my door at noon on Tuesday! He included the necessary gasket and washers.
- 3 quarts of gear oil. As recommended, I used non-synth 85w140 since it doesn't often get cold in Texas- and when it does I'm usually not driving the '65. I would recommend buying the quart size containers (vs. a gallon) for reasons described below.
- Gasket sealer- the blue stuff should work fine (I used some oil resistant black stuff I had in the garage).
The result:
No more "tunk, tunk!" The old carrier allowed the pinion to wobble a bit- and I'm sure that was the cause of the noise. The back end of the car feels really solid now. The 3.55 is PERFECTION with my inline six and T5 transmission. I've previously owned a '65 C-code automatic (2.80 rear end) and the setup I have now feels a lot crisper off the line. I will never "fear the gear" again, I've had a 2.80 in this car, then a 3.20, and now a 3.55. (I think the next step up is 3.90... hmmm).
I do still have some resonance thrumming at various speeds, which I think I can resolve by tinkering with the pinion angle (since changing the angle changes the thrumming). Update- I was able to virtually eliminate the resonance thrumming by setting the pinion angle back to flat AND by reinstalling my lowering blocks (I believe the blocks help in decreasing the angle of the driveshaft between the trans tail and pinion). I also need to swap the speedo gear out on the T5, because it is reading about 10% fast now. The '85-89 V8 T-5 trans in my car has a 7 tooth speedometer gear, so the correct driven (cable) gear should be the 20 tooth (I had an 18 tooth driven gear with the 3.25).
The process:
1. Lift the back and remove the rear wheels (remember to chock the front wheels). I would recommend getting the car fairly high up, since you'll want to use a small trolley jack to support the chunks as you remove & install.
2. Remove the axles. There's a hole in the mounting plate at the end of the axle- line it up with the four bolts (9/16") on the bearing retaining plate to remove it. Then give the axle a good yank. If it doesn't pop right out, you can turn the drum around, loosely install some lugs, and use the drum as a slide hammer (pictured). As you pull the axle out, support it so it doesn't damage your axle seals. You don't have to remove any of the brake hardware.
3. Disconnect the bolts (1/2") that hold the u-joint to the pinion. Put some tape around the two newly freed u-joint bearings. Otherwise, if the cap pops off, you're likely to have needle bearings all over the place. I just lowered the back end of the driveshaft and moved it to the side.
4. Place an oil catch under the diff, and remove the 10 bolts that hold it on. I left one bolt on the side loose, and then carefully used a chisel to pop loose the seal (actually, I used my big hammer to work the chisel in between the axle housing and chunk... I've been told this can score the housing and cause a leak- so its better to just whack on the side of the pinion housing with a dead blow hammer until it releases from the seal) . Allow the gear oil to drain into your pan.
5. Once the seal is released, the diff will come off. If 60-70 lbs is not heavy for you, fine- otherwise, the diff could be described as heavy. I found it was much easier to remove (you have to slide it straight forward due to the 10 studs it sits on) by using a trolley jack to support some of the weight. Just be aware that when it finally clears the axle housing, gravity will come into effect.
6. Scrape all the old seal off the axle housing. Apply gasket seal (blue or black) to one side of the gasket, and put the sealed side onto the axle housing.
7. Apply gasket seal to the new differential mounting surface and then install on the 10 studs (again, a trolley jack helped me a lot).
8. Reinstall the 10 washers and/or bolts. Not sure what the torque specs are, but I noticed mine weren't super tight when I removed them, so I didn't go nuts making them super tight when I reinstalled.
9. Slide the axles back in (again, being careful not to damage your axle seals). In fact, its a good time to inspect your axle seals, bearings, and the gaskets on your bearing retainer plate. If the bearings spin really easily, they're at the end of their life (there should be smooth resistance as you rotate the bearing around the axle).
10. Reinstall the bearing retainer plates and wheels.
11. Install 2.5-3.0 quarts of gear oil. To get better access, I relocated my jacks to the rear frame rails and let the axle come down with the trolley jack. This gives better access. BTW, there are two possible locations for the fill plug. The early axles had the plug on the back of the axle housing- but no plug on the diff carrier. The later axles were vice versa. This is important to know, because if you have a later axle housing and install an early diff carrier, you'll have no fill plug. The '67+ diff carrier is stronger anyway (and will fit either the early or late axle carriers) so that's the surefire way to go.
Adding the gear oil was actually the hardest step in the process for me! I bought the gallon container, which was a mistake. 85w140 is like molasses at 45 degrees (the temp in my garage), so my siphon tube wouldn't move the stuff. Trying to use a funnel was comical (now, not at the time) and resulted in a bunch of oil all over the garage floor- but none in the diff! Finally, I went and purchased one quart, put that in, then refilled the bottle twice.
12. Reinstall the fill plug.
13. Reinstall the u-joint to the pinion.
14. Get the car out of the air and enjoy.
