How to install a diff in your GEN II

[Boosted Motorsports]

In this video I show how I changed the differential in my Viper to a Mopar Performance 3.73.

Install is pretty straight forward and would be much easier with a lift and power tools but this video shows that it can be done in your own garage.

Check back on YouTube for more videos uploaded every few days! In car review video also coming soon once gears are broken in but so far it is a HUGE upgrade to the car and my most favorite mod yet. ;)


https://youtu.be/l4GzvLueOqs

[My98RT10]

Awesome video, thanks a lot for sharing! I've always wondered how heavy the diff is? Seems like you can hold the weight alone and don't need second person...? I still have this project ahead of me.... will do 3.55 though...

[Boosted Motorsports]

Awesome video, thanks a lot for sharing! I've always wondered how heavy the diff is? Seems like you can hold the weight alone and don't need second person...? I still have this project ahead of me.... will do 3.55 though...

It definitely isn't light and had a buddy obviously giving me a hand but only one of us could fit under there at a time. I used the floor jack with a block of wood to throw it back up there and i guided it up. Only fun part is manipulating the diff to get the "batwing" to clear the 2 frame rails as it is much wider than the space given.

Unless you are going forced induction don't bother with 3.55. The 3.73 is not excessive whatsoever and makes the car much quicker and fun to drive. I'm actually dreading when I upgrade to new wheels as my gear ratio will effectively be around 3.55 and not be as good as it is now...

If you have ever driven any performance sports car with a good transmission gear ratio the 3.73s feel right at home.

[My98RT10]

I have the gears already so will stick to 3.55 I guess...

I do have a few more questions, if you don't mind:
- how hard was it to loosen the 8mm bolts of the drive and half shafts?
- could you reuse them or did you take new bolts?

Thanks again, looking forward to your review once broken in...!

[Chris1]

It definitely isn't light and had a buddy obviously giving me a hand but only one of us could fit under there at a time. I used the floor jack with a block of wood to throw it back up there and i guided it up. Only fun part is manipulating the diff to get the "batwing" to clear the 2 frame rails as it is much wider than the space given.

Unless you are going forced induction don't bother with 3.55. The 3.73 is not excessive whatsoever and makes the car much quicker and fun to drive. I'm actually dreading when I upgrade to new wheels as my gear ratio will effectively be around 3.55 and not be as good as it is now...

If you have ever driven any performance sports car with a good transmission gear ratio the 3.73s feel right at home.

Very nice video. Does Mopar make the 3.73 Performance Rear for a 96 RT/10 as well? That seemed like a pretty straight forward removal and installation, except for the exhaust. lol.

[heath1225]

I just bought one as well!

[dave6666]

Awesome video, thanks a lot for sharing! I've always wondered how heavy the diff is? Seems like you can hold the weight alone and don't need second person...? I still have this project ahead of me.... will do 3.55 though...

Did mine diff swap by myself. No need for a helper.

[dave6666]

In this video I show how I changed the differential in my Viper to a Mopar Performance 3.73.

Install is pretty straight forward and would be much easier with a lift and power tools but this video shows that it can be done in your own garage.

Check back on YouTube for more videos uploaded every few days! In car review video also coming soon once gears are broken in but so far it is a HUGE upgrade to the car and my most favorite mod yet. ;)


https://youtu.be/l4GzvLueOqs

So what does the "Mopar Performance 3.73" come with? Is it just gears, or does it come with a better LSD than the stock Dana one? Which if you've changed it you'll notice the lackluster performance of the Dana LSD.

[Boosted Motorsports]

I have the gears already so will stick to 3.55 I guess...

I do have a few more questions, if you don't mind:
- how hard was it to loosen the 8mm bolts of the drive and half shafts?
- could you reuse them or did you take new bolts?

Thanks again, looking forward to your review once broken in...!

- The 8mm bolts have (insert age of car here) old loctite on them so they could be a bit of a pain to remove but didn't cause me any issues. Make sure you have your wrench/socket fully on the bolt head when cracking them loose to avoid rounding.
- Common opinion is to replace the U-joint straps with new whenever being removed. Some people re-use but it known to be a failure point if you do.


Very nice video. Does Mopar make the 3.73 Performance Rear for a 96 RT/10 as well? That seemed like a pretty straight forward removal and installation, except for the exhaust. lol.
Yes 96-02 uses this exact same diff. I know some people said 96 was an odd year for RT/10s with being a "between generations" year but someone else may know better on this.



I just bought one as well!

Nice!!! Let me know how you like it!


So what does the "Mopar Performance 3.73" come with? Is it just gears, or does it come with a better LSD than the stock Dana one? Which if you've changed it you'll notice the lackluster performance of the Dana LSD.

DC chimed in on a previous thread and said it is still the factory LSD except has the upgraded 01-02 larger carrier bolts for better strength. Might look into a better LSD in the future as you said!

[98RedGTS]

Thanks for the video and the quick BC review as well. Removing the Diff actually looks more straight forward than I was thinking it would be.

Question though - Did you give up on trying to locate polly bushings for it? Looked like you installed everything back together with the factory ones still in place.

[My98RT10]

At 2:23 in your video you are loosening (removing??) the center bolts that connect the diff to the pinion crossmember. But obviously you removed also the pinion crossmember from the frame as could be seen later in the video. So was it required to loosen these bolts at all to take out the diff?

I am just wondering, what is the best way to take out the diff and if the pinion crossmember needs to be removed from the frame or can stay where it is....!?!? Thanks!

[BrianACR]

Great video!! Again :)
Just wondering when you're gonna do the 'how to install a lift in your garage' video? Lol :smilielol:

[Boosted Motorsports]

Thanks for the video and the quick BC review as well. Removing the Diff actually looks more straight forward than I was thinking it would be.

Question though - Did you give up on trying to locate polly bushings for it? Looked like you installed everything back together with the factory ones still in place.

You're correct! Luckily they seemed to be in decent shape for now so I didn't bother at this time. I heard someone say they tried Energy Suspension bushings for the C4 vette in the batwing but they got pounded out quickly. Not sure how true that is or not. I did actually take measurements of the bushings that are in the diff mounts on all 4 which I may do some research on. I don't feel like taking that diff out again anytime soon though without a lift lol.



At 2:23 in your video you are loosening (removing??) the center bolts that connect the diff to the pinion crossmember. But obviously you removed also the pinion crossmember from the frame as could be seen later in the video. So was it required to loosen these bolts at all to take out the diff?

I am just wondering, what is the best way to take out the diff and if the pinion crossmember needs to be removed from the frame or can stay where it is....!?!? Thanks!

Good eye! I did begin by loosening those bolts but they have a nut on the top that you have to get a wrench on. You could just stick your hands up and remove the two rubber mounted bushing bolts which we ended up doing. I was just trying to save having reach way up to those rubber mounts but I ended up doing it anyway.

On this note I would also leave that mount loose on the diff during install. There is quite a bit of play from that mount->diff and I didn't want to be fighting it while putting the diff up in the car. Once all the bolts on the rubber mounts were in and tight, I then tightened up the mount->diff.

In your case if you are re-using your diff then you dont have to remove that mount if you want to avoid doing so. With me swapping diff housing it had to be loosened anyways :D


Great video!! Again :)
Just wondering when you're gonna do the 'how to install a lift in your garage' video? Lol :smilielol:

Hopefully sooner than later Brian! :D At this rate though is there anything else I need to be under the car for? lol

[plumcrazy]

copied this thread to the HOW TO section. nice job !

[Chris1]

[QUOTE=Boosted Motorsports;284178]- The 8mm bolts have (insert age of car here) old loctite on them so they could be a bit of a pain to remove but didn't cause me any issues. Make sure you have your wrench/socket fully on the bolt head when cracking them loose to avoid rounding.
- Common opinion is to replace the U-joint straps with new whenever being removed. Some people re-use but it known to be a failure point if you do.


Yes 96-02 uses this exact same diff. I know some people said 96 was an odd year for RT/10s with being a "between generations" year but someone else may know better on this.


Where did you wind up purchasing it from if you don't mind me asking? I may give them a call to verify if this will fit and get pricing as well.

[99RT10]

I thought the 92-2000 reared (dana 44) were the same (although the Gen 1 had more casting on top), 01-02 were different (super dana 44)?

[Fatboy 18]

Here's a a pic of the stock 307 2000 Gen II rear diff
https://c1.staticflickr.com/9/8088/8586365769_fab4ef14bd_b.jpg (https://flic.kr/p/e5Knp8)Gen2 OEM rear diff 307 gears (https://flic.kr/p/e5Knp8) by Fatboy 18 (https://www.flickr.com/photos/90582394@N02/), on Flickr

https://c1.staticflickr.com/9/8505/8587503492_039660c51b_b.jpg (https://flic.kr/p/e5RcB3)Ipod camera roll download 05.03.2013 063 (https://flic.kr/p/e5RcB3) by Fatboy 18 (https://www.flickr.com/photos/90582394@N02/), on Flickr

[My98RT10]

Here's a pic of my 1998 diff ;)

I managed to pull it today to get 3.55 gears installed. Man, what a PITA to get it out in my tiny garage with just some jack stands... this is the last project of this sort... I think my bones are just too old for this kind of "work out" LOL...

http://i1359.photobucket.com/albums/q800/My98ViperRT10/Differential/DSC_0977_zpslkekn6om.jpg

[My98RT10]

Good eye! I did begin by loosening those bolts but they have a nut on the top that you have to get a wrench on. You could just stick your hands up and remove the two rubber mounted bushing bolts which we ended up doing. I was just trying to save having reach way up to those rubber mounts but I ended up doing it anyway.

On this note I would also leave that mount loose on the diff during install. There is quite a bit of play from that mount->diff and I didn't want to be fighting it while putting the diff up in the car. Once all the bolts on the rubber mounts were in and tight, I then tightened up the mount->diff.

In your case if you are re-using your diff then you dont have to remove that mount if you want to avoid doing so. With me swapping diff housing it had to be loosened anyways

Thanks John. Now that I have the diff out I am wondering I you have loctited the main 4 mounting nuts when putting the diff back into the car? Also, did you apply a specific torque when fastening them? The shop manual doesn't mention anything....?

EDIT/UPDATE: I need to correct myself... after looking again at the shop manual it states 135 Nm for the 4 mounting bolts. But nothing with regards to using Loctite so I believe it is not required...

[Boosted Motorsports]

Thanks John. Now that I have the diff out I am wondering I you have loctited the main 4 mounting nuts when putting the diff back into the car? Also, did you apply a specific torque when fastening them? The shop manual doesn't mention anything....?

EDIT/UPDATE: I need to correct myself... after looking again at the shop manual it states 135 Nm for the 4 mounting bolts. But nothing with regards to using Loctite so I believe it is not required...

No loctite is necessary on the factory nuts/bolts that hold the 4 diff mounts. They are factory fasteners that have a "loctite" mechanism designed into them by the ending threads being an oblong shape. Either way if you added loctite you won't hurt anything. :)

[Chris1]

Here's a pic of my 1998 diff ;)

I managed to pull it today to get 3.55 gears installed. Man, what a PITA to get it out in my tiny garage with just some jack stands... this is the last project of this sort... I think my bones are just too old for this kind of "work out" LOL...

http://i1359.photobucket.com/albums/q800/My98ViperRT10/Differential/DSC_0977_zpslkekn6om.jpg


In conjunction with Boosted's video, any other tips and timesavers you can recommend? I am think about getting a 3.55 complete rear to swap in/out. Most of the time, the "first time" is usually the hardest, since that's where all the learning's come in. Did it make sense to put it a little higher on jack stands in order to make it easier to get out, although I guess it's a trade off then having to lift the diff that much higher in the air to get it back in place? In the '96 manual, it only lists 7 steps, 2 of them being removing the belly pan and removing the driveshaft from the vehicle. In the video, the driveshaft looks like it's just been disconnected similar to the half shafts, and just moved out of the way slightly.

[My98RT10]

In conjunction with Boosted's video, any other tips and timesavers you can recommend? I am think about getting a 3.55 complete rear to swap in/out. Most of the time, the "first time" is usually the hardest, since that's where all the learning's come in. Did it make sense to put it a little higher on jack stands in order to make it easier to get out, although I guess it's a trade off then having to lift the diff that much higher in the air to get it back in place? In the '96 manual, it only lists 7 steps, 2 of them being removing the belly pan and removing the driveshaft from the vehicle. In the video, the driveshaft looks like it's just been disconnected similar to the half shafts, and just moved out of the way slightly.

One thing is clear: I don't want to do it a second time.... (apart from the re-install). I think, putting it a bit higher will not make a real difference. What makes a difference, of course, is doing it on a real lift and with 2 persons. For me, the most difficult part was to get the thing to pass by the main frame rails as the "wing" is much wider than the clearance between these 2 rails. Although, I managed to get it out with both half-shafts in place (!) I strongly recommend to remove at least one half-shaft completely from the vehicle. This way, you'll have much more room on this side for maneuvering the pumpkin out.

BTW: somewhere I read that the diff weighs around 70 pounds. So be prepared when starting to juggle this thing.... I made sure not to place myself under the diff when getting it out and used the floor jack to carry the weight until it came out.

[My98RT10]

John, I hope you don't mind if I post some updates of my diff swap here in your thread. If you do, no problem, I'll open a new one. I just thought that this way others get more information in one place...

I was thinking quite some time to whom to give the pumpkin for swapping the gears as I don't trust any regular shop to do the job right. I finally decided to give it to Mintgen Motorsport which is located very closely to the Ring, so a 1.5 h drive for me. They are one of the few here in Germany knowing Vipers also as a race car. The owner told me also about his involvement in setting the lap record some years ago. Very interesting! So, I believe I am in good hands and will start the re-install today.

Let's see how far I get...:confused:

[Boosted Motorsports]

John, I hope you don't mind if I post some updates of my diff swap here in your thread. If you do, no problem, I'll open a new one. I just thought that this way others get more information in one place...

I was thinking quite some time to whom to give the pumpkin for swapping the gears as I don't trust any regular shop to do the job right. I finally decided to give it to Mintgen Motorsport which is located very closely to the Ring, so a 1.5 h drive for me. They are one of the few here in Germany knowing Vipers also as a race car. The owner told me also about his involvement in setting the lap record some years ago. Very interesting! So, I believe I am in good hands and will start the re-install today.

Let's see how far I get...:confused:

The more information the better!

You're going to love the gear change. Well worth the $

[My98RT10]

Just a bit of an update from my gear change project...

So I got the diff back last Saturday and immediately startet to install it. The days before I was thinking what could be the best way to get the thing back in, given the width of the wing and the limited clearance between the frame rails. My idea was to lift the right side of the wing high up in the air and start lifting it not from the middle of the car but a bit more on the right side so that the left part of the wing could pass the left frame rail when lifting it up. To my surprise, this worked perfectly fine! No problem at all. Before, I was convinced that this would be the trickiest step of the re-install!

Here's a pick of the starting point. I should mention that I removed the right half-shaft so I had enough room in that upper right corner for the diff wing.

http://i1359.photobucket.com/albums/q800/My98ViperRT10/Differential/DSC_1009_zpsj93tixag.jpg

However, one minor problem came up when I tried to position the diff into those brackets where you bolt it to the frame. I first aligned the wing to its frame brackets so I could push the bolts in. Unfortunately, in this position the pinion crossmember did not line up with its brackets so I could not get these bolts in. I then remembered, that the guy at the shop mentioned, that he had removed the pinion crossmember so that he could bolt the diff to some fixture for the gear swap. He tried to reinstall the crossmember as it was before but obviously, this wasn't the case. I did not want to lower the diff again so I had to loosen the bolts connecting the crossmember to the main diff housing but the nuts on top are not easy to come by in this position. But as said, that was a minor problem just consuming some more time.

Here are some more pics:

http://i1359.photobucket.com/albums/q800/My98ViperRT10/Differential/DSC_1013_zps7htucvg5.jpg

http://i1359.photobucket.com/albums/q800/My98ViperRT10/Differential/DSC_1020_zpsyhptsxbz.jpg

Connecting the drive- and half-shafts was straight forward. I am currently putting the exhaust back on. Unfortunately, I had to remove the complete system including cats as I was not able to remove the rear muffler unit alone. This is now the worst part of the re-install.

I hope I will be ready for a first drive this coming weekend. You can probably imagine, how impatient I am to experience the difference... ;-)

[Boosted Motorsports]

Nice work My98RT10!!

I installed my diff the same way you did with the pass side of the batwing higher than the drivers side. I also used the same method of putting it on the floor jack and lifting it. I actually had recorded doing this but it somehow did not save on my camera.

You'll definitely like the change! Go easy on it for the first 500 or so miles and then replace the fluid. But even just putting around and not launching or doing anything too shocking to the drivetrain you will notice a major difference!

[Jack B]

One little hint, use a thread chaser (not tap) to clean the driveshaft threads. secondly, the new driveshaft bolts you purchase may have been on the shelf for a long time, use a wire wheel and clean off the new/old loctite and reapply new loctite. This makes the reinstall go easier. the hardened loctite can actually strip the driveshaft stub.

[My98RT10]

In my case, I used new bolts that had no Loctite on them. So I preped them with fresh Loctite prior to install. Also, I screwed them in "dry" first to test fit. No problems whatsoever. The new bolts were part of the strap kit coming with the complete installation set I bought from Unitrax. These new bolts (M8x1x20, grade 12.9) were actually Allen head bolts as opposed to the hex bolts installed by the factory.

[My98RT10]

Nice work My98RT10!!

I installed my diff the same way you did with the pass side of the batwing higher than the drivers side. I also used the same method of putting it on the floor jack and lifting it. I actually had recorded doing this but it somehow did not save on my camera.

You'll definitely like the change! Go easy on it for the first 500 or so miles and then replace the fluid. But even just putting around and not launching or doing anything too shocking to the drivetrain you will notice a major difference!

Thanks! I'm drooling, can't wait... ;)

[Boosted Motorsports]

One little hint, use a thread chaser (not tap) to clean the driveshaft threads. secondly, the new driveshaft bolts you purchase may have been on the shelf for a long time, use a wire wheel and clean off the new/old loctite and reapply new loctite. This makes the reinstall go easier. the hardened loctite can actually strip the driveshaft stub.

This is great advice Jack! The loctite on the new Spicer U joint bolts totally sucked and would have been much simpler applying some new liquid loctite to clean threads.

[Goatman]

Hey Boosted,

What was the PN for the Mopar 3.55 Diff?

[My98RT10]

Hey Boosted,

What was the PN for the Mopar 3.55 Diff?

I think his is a 3.73...

[My98RT10]

Maybe there's one important thing to be mentioned regarding the strap bolts: If you buy a 1350 strap kit directly from Spicer (which is OEM) you need to buy the version with metric bolts. The regular 1350 strap kit comes with imperial bolts and is significantly cheaper. The dangerous thing is that you can screw the imperial bolt into the Viper yoke quite a bit without a noticable problem. But you very likely harm or ruin the threats in your Viper yoke if you don't use metric bolts.

[Boosted Motorsports]

Hey Boosted,

What was the PN for the Mopar 3.55 Diff?

It is a 3.73 but it is long discontinued from Mopar. I don't have a part number for it as even though it was still new I bought it second hand from someone else that never used it.


I think his is a 3.73...

Good eye! :D

[My98RT10]

I think it is time for anow update from my side...

I finished the re-installation of my 3.55 diff this weekend and took her out for a drive. Following the break in instructions I didn't go very fast nor aggressive. I have to say that I did not notice too much of a difference in terms of thrust. But I believe, I will once I can unleash her again. I did notice the gap of the speedometer readings though ;)

I didn't notice any noises either, so the gears seem to be set up correctly.

Will provide an update after the collection of unspirited miles has come to an end....

[heath1225]

I think it is time for anow update from my side...

I finished the re-installation of my 3.55 diff this weekend and took her out for a drive. Following the break in instructions I didn't go very fast nor aggressive. I have to say that I did not notice too much of a difference in terms of thrust. But I believe, I will once I can unleash her again. I did notice the gap of the speedometer readings though ;)

I didn't notice any noises either, so the gears seem to be set up correctly.

Will provide an update after the collection of unspirited miles has come to an end....

You'll notice a difference when you get on it. TRUST ME.

[My98RT10]

You'll notice a difference when you get on it. TRUST ME.

I will trust you!! ;) ;) ;)
:drive:

[My98RT10]

Question to John: how did you adjust the speedo after the gear change?

I tested the difference. In my case when driving 50 mph according to the speedometer my GPS showed 44 mph. You should be even more off, right?

[Boosted Motorsports]

Question to John: how did you adjust the speedo after the gear change?

I tested the difference. In my case when driving 50 mph according to the speedometer my GPS showed 44 mph. You should be even more off, right?

I still have not corrected this. Most people use a "yellow box" but I have heard there may be a way to correct this through the PCM. Hasn't bothered me so far but definitely will address this soon :)

[My98RT10]

I still have not corrected this. Most people use a "yellow box" but I have heard there may be a way to correct this through the PCM. Hasn't bothered me so far but definitely will address this soon :)

Yes, Dan Cragin confirmed to me, that he can do it with a tune. That would be my preferred way, too ... let us know, once you have done it ;-) Thanks!