V8 Roadsters Cadillac Getrag Differential. INSTALLED. - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-03-2015, 12:16 AM   #21
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Wow I love that front brace/mount. Want to make another one for me?
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Old 03-03-2015, 01:13 AM   #22
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Wow I love that front brace/mount. Want to make another one for me?
Charlie. What's the status on your axles? Did you see my comment about how to install them properly with the circlip gap facing up when you push the axles into the diff?

And I don't know if I'll be making any of those for anyone else. Took me like at least 4 hours. I do have the template for it though.
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Old 03-03-2015, 07:51 AM   #23
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Shane,

Well definitely don't get rid of the templates, you made a very nice piece there.

My axles are in and have similar gap to yours. I didn't see your circlip comment until after I had installed them but I am fairly certain they are all the way in. I drove the car around my neighborhood yesterday. Seems okay, few little issues.

-Some clunking around back there when starting off (which I believe is from the PPF needing a bit more trimming or possibly the diff needing that front bracing as you have added)
-knocking noise on hard left turns (sounds like maybe exhaust needing some adjustmenting, will address this week)
-Good bit of added NVH from the swap, did you have this experience? Specifically on power. I listened to videos of CTS-V diff whine and I'm not quite convinced that's what it is.
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Old 03-03-2015, 05:30 PM   #24
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Shane,

Well definitely don't get rid of the templates, you made a very nice piece there.

My axles are in and have similar gap to yours. I didn't see your circlip comment until after I had installed them but I am fairly certain they are all the way in. I drove the car around my neighborhood yesterday. Seems okay, few little issues.

-Some clunking around back there when starting off (which I believe is from the PPF needing a bit more trimming or possibly the diff needing that front bracing as you have added)
-knocking noise on hard left turns (sounds like maybe exhaust needing some adjustmenting, will address this week)
-Good bit of added NVH from the swap, did you have this experience? Specifically on power. I listened to videos of CTS-V diff whine and I'm not quite convinced that's what it is.
Glad you got it driving around. Trust me. Once you trim the PPF more, things will still clunk. Even after you get that taken care of, the lash in the gears is probably going to clunk too. I hear it all now thanks to that front brace.

Also about gear whine. It sounds like there is a large variance in how much people hear. I didn't hardly hear any until said brace. I used to just hear it from 40-60. Now that sounds about the same, but I can also hear it a little as speed increases. Plus now from like 20-100+ there is a very high pitch but quietish sound that seems like it's being transmitted through my roll bar. I am going to try and get a little urethane between the brace and the factory ladder bar bracing.
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Old 03-03-2015, 07:22 PM   #25
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That's really disappointing to hear about the clunking, was hoping to have this be a pretty invisible mod as this is still a street car. I wonder if getting a new diff from GM is worth considering. Considering the weight difference from a CTS I would assume the differential will have a much longer lifespan.

I was also looking at how they mount the front of the diff on the V8 cars. It appears they weld a tab on the subframe to bolt into the front bushing. I wonder if something like this could be done here.
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Old 03-03-2015, 07:38 PM   #26
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Yeah. That's exactly what they do with the V8 kits. And I'm kind of doing the same thing as the bracket I made. I was talking to someone who actually has the V8 kit with the 3.42 ratio and he says his is pretty noise in regard to gear whine.

But I definitely wouldn't take my word as final as far as the clunking and whining goes. This is all still pretty new here.

After you get some more time on it, let me know how much the shifter moves around when you load and unload the motor.
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Old 03-03-2015, 08:46 PM   #27
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How many miles were on the diff you got Shane?
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Old 03-03-2015, 09:15 PM   #28
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How many miles were on the diff you got Shane?
Supposedly 20k. But looks like it has less.
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Old 03-04-2015, 02:11 PM   #29
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Also figure around $1000 for the labor to swap out the gears.
I don't see how you get a grand for labor to swap the gears. Even with bay area labor rates, doing mine at the "rear end speciality" shop only ran $300 (pull the diff at home, take it to the shop with the gears, have them put them in and set the lash/etc).

There are a bunch of good reasons to use the V8R CTS diff, but I don't think cost compared to a Mazda 3.636 is really one of them.

--Ian
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Old 03-04-2015, 03:26 PM   #30
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I don't see how you get a grand for labor to swap the gears. Even with bay area labor rates, doing mine at the "rear end speciality" shop only ran $300 (pull the diff at home, take it to the shop with the gears, have them put them in and set the lash/etc).

There are a bunch of good reasons to use the V8R CTS diff, but I don't think cost compared to a Mazda 3.636 is really one of them.

--Ian
You're right. After reading around some more, $1000 sounds way too expensive. I just have little faith in the gear shops around our area, which was one of the main factors of why I never even tried to in stall the 3.63s I had.

If you have good vendors in your area like Puttymod, then that may be worth it as you won't be worried about having to pull the diff multiple times for the diff shop to get their **** right.
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Old 03-04-2015, 04:27 PM   #31
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Originally Posted by cmalouf View Post
That's really disappointing to hear about the clunking, was hoping to have this be a pretty invisible mod as this is still a street car. I wonder if getting a new diff from GM is worth considering. Considering the weight difference from a CTS I would assume the differential will have a much longer lifespan.

I was also looking at how they mount the front of the diff on the V8 cars. It appears they weld a tab on the subframe to bolt into the front bushing. I wonder if something like this could be done here.
It appears V8roadsters has some work to do as far as a good mounting solution for this differential. Making your own custom front brace after already purchasing this solution shouldn't even be an option.
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Old 03-16-2015, 04:09 PM   #32
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Here is another look at the getrag kit.

minute 3:00-7:30 ish.
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Old 03-16-2015, 04:13 PM   #33
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Nice vid.

I'm exploring utilizing the weld-in mounting tabs with the ppf setup.

While the car drives well now, I agree with Shane that there's too much motion of both pinion and shifter (thus trans) during hard driving, especially with abrupt weight/force changes.
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Old 03-16-2015, 07:01 PM   #34
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Nice vid.

I'm exploring utilizing the weld-in mounting tabs with the ppf setup.

While the car drives well now, I agree with Shane that there's too much motion of both pinion and shifter (thus trans) during hard driving, especially with abrupt weight/force changes.
Hey Charlie! I was wondering when you were going to chime back in with some progress information. I too looked at the idea of trying to use the weld in front pinion brackets with the PPF. But it really doesn't look like there is an easy way to do it. There's not much room and as I remember it, the PPF is completely in the way. Which led me to my design.

Also my passenger side axle seal started leaking a bit more so I replaced with with a new GM one. I can't believe how easy it is. With a lift, I took the wheel off, unbolted the top bolt of the hub, loosened the lower, pulled off the ABS line, popped the axle out, replaced the seal and had it back together in probably 30-45 min.
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Old 03-16-2015, 07:06 PM   #35
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It's funny, my passenger side axle seal is leaking too. I have one waiting to go in, glad to hear it's an easy process.

Are you happy with how your mounting solution has turned out?
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Old 03-16-2015, 07:53 PM   #36
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Here is another look at the getrag kit.

minute 3:00-7:30 ish.
Looking at that diff compared to the one I got, now I know why I had clearance issues. Case is way different.
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Old 03-17-2015, 06:53 PM   #37
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Looking at that diff compared to the one I got, now I know why I had clearance issues. Case is way different.
How is your kit coming along? Did the front pinion mount work out ok?
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Old 03-17-2015, 10:45 PM   #38
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How is your kit coming along? Did the front pinion mount work out ok?
Haven't had much time to work on the car. Just got the engine set back in. Planning to install the rearend Sunday.
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Old 03-18-2015, 12:05 AM   #39
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Haven't had much time to work on the car. Just got the engine set back in. Planning to install the rearend Sunday.
My main advice is, if you don't have a lift and tranny jack, try to remove as much material from the diff case and the PPF as possible the first time. That way you're not having to pull the assembly in and out of the car multiple times.

Not having a template, I had to do this.
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Old 03-20-2015, 01:02 AM   #40
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Well, ran into a bit of a problem. The PPF was very close to our custom fuel cell. Apparently the getrag set up moves the rear of the PPF over a little and now there's interference and it won't go in place. What doesn't make sense is that if the rear of the PPF is over further, I don't know how the mounting holes for the tranny could still line up. Moving the rear over would cause the front set of holes and rear set of holes to no longer be parallel to each other.
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