Torsen done

[Cman01]

yes im sure bud, little do you know that i never broke a diff....just the f888390 twice....same diff everytime put in the stronger f988390 which i suggested you do and never had an issue again...diff was stock 2010 and stock factory 31spline axels...and for your info that diff had around 1200 passes total....but to each there own. cheers!

Hey, I just remember you posting about breaking the rear end on the local MB here:

http://www.gtamc.com/showthread.php?125208-GT500-Rear-End-Carnage-Today-OOOOOPS!&highlight=

I guess when you had it opened up it was the ring and pinion and not the rear end that broke (which to me refers to the diff).

Famous quote from Peter O'toole "If you don't say what you mean you don't mean what you say."

 

[Cman01]

Well, the weekend didn't go as planned...

My first run, I launched at 4k rpm expecting tire spin but wanted to feel if there was any difference in my old Torsen and the new Wavetrac. It bit so hard I bogged! Same tires as last drag meet, similar hot conditions, 18psi. No tire spin at all. So, obviously, i'm like...this is gonna be a good day! So, next time up I decide to launch at 4500 with same tire pressure. Boom!

I have a video of it, but as soon as the light changed I released the clutch...it bit hard, then an explosion and a sound like someone tossed a handful of nuts and bolts into a blender. It hasn't been opened up yet, but will tomorrow. I will keep you all posted on what we find. Have a feeling the gear set broke (3.90 Motive as well.... )But, my initial feeling was that things were vastly improved over the last meet on the Torsen with the new Wavetrac....unless I find it's the Wavetrac that gave way. Anyways, enough guessing till tomorrow...

https://youtu.be/BKCXiMM8ick

If you open it up and do find out that the ring and pinion did break post up which motive 3:90 gear set you put in (either the f888390 or f988390).

Good luck fixing it, hopefully it's not as bad as it seems.

 

[Softballer77]

If you open it up and do find out that the ring and pinion did break post up which motive 3:90 gear set you put in (either the f888390 or f988390).

Good luck fixing it, hopefully it's not as bad as it seems.

I looked it up, and it is the f888390.

 

[Bad Company]

Great info BC, total next level as usual.

I do think you can get gun drilled lightened 35 spline axles.

I built the best street/strip 8.8 at the time and used a 33-spline Trutrac, if I were doing it today, it would get a 35-spline S-trac. The weight and torque our manual trans Shelbys can deliver is unique in many ways, my chassis shop wanted 35 splines if possible.

He actually recommended a 9" swap, and if I did it again today, I'd have taken that advice based on gear whine.
I haven't launched on my redone fully braced 33-spline 8.8, but if it whines I'm going 9"
-J
:beer:

LOL

Thanks J

Sometimes I think as I've gotten older that I should have paid a lot more attention in my high school trigonometry classes and been motivated to college to become a mechanical engineer. Than applied that to the love of playing with cars and guns. Especially after field stripping a high end custom pistol this morning and finding a cracked slide.

I doubt at your power level you'll break anything with the 33 spline combo. What I saw when I tore my rear apart is the carrier shims and carrier bearing pre-load is a major issue with the 8.8. None of the aftermarket shim kits work to pre-load the carrier bearings properly. You must purchase the Ford solid one piece shim oversized by 0.006" and drive it into place. Otherwise the carrier is going to move and change both the gear wear pattern and backlash. There is no other way to install the carrier and pre-load the carrier bearings properly in my opinion.

Unfortunately Strange doesn't start gun drilling axles, until you go to a 40 spline axle. Again they're looking at the fact they have to increase diameter to be able to add the extra splines. As diameter increases so does strength. So this allows them to gun drill the axle without loosing structural integrity. To gun drill the 35 spline axlemay be asking to break it easily. Also looking at Strange's website the 40 spline gun drilled axles are strictly meant for drag race applications with a different alloy

The 9" is tough and can handle a bunch of power without any issues. The down side is the added weight

 

[Bad Company]

Well, the weekend didn't go as planned...

My first run, I launched at 4k rpm expecting tire spin but wanted to feel if there was any difference in my old Torsen and the new Wavetrac. It bit so hard I bogged! Same tires as last drag meet, similar hot conditions, 18psi. No tire spin at all. So, obviously, i'm like...this is gonna be a good day! So, next time up I decide to launch at 4500 with same tire pressure. Boom!

I have a video of it, but as soon as the light changed I released the clutch...it bit hard, then an explosion and a sound like someone tossed a handful of nuts and bolts into a blender. It hasn't been opened up yet, but will tomorrow. I will keep you all posted on what we find. Have a feeling the gear set broke (3.90 Motive as well.... )But, my initial feeling was that things were vastly improved over the last meet on the Torsen with the new Wavetrac....unless I find it's the Wavetrac that gave way. Anyways, enough guessing till tomorrow...

https://youtu.be/BKCXiMM8ick

I'm afraid it may be the Wavetrac. The 31 spline Wavetrac isn't holding up from what I've heard from others. If it is the Wavetrac and you decide to keep the 8.8 tell whomever you bought it from that you'll pay the price difference and upgrade to the 33 spline. You'll need new 33 spline axles with the 9" bearing ends from Moser, plus the 8.8 to 9" wheel end bearing housings to retain the stock brakes

Here are a few pictures of what you'll need to do with the axle tubes and bearing housing to retain the stock brakes

I'm sorry for the poor picture quality I was trying to stoop over and I guess I was too shaky with the phone as a camera

 

[ALLKHEINZ]

I looked it up, and it is the f888390.

hate to be the bearer of bad news BUT the f888390 will last a little while but you will break them.....after myself, paul mitchell and a few of the BPS clan broke several sets i personally put a call into Motive...was told that with the weight and power the cars we had the gears in that they would break and suprised i got that much time out of them....they said go with the f988390 which were stronger rated for higher HP and weight....went that route never had an issue again.

 

[ALLKHEINZ]

Re: Cman01

Ring and Pinion is part of the Rear End is it not? so i did say what i meant, before you jump the gun it might be a good idea to find out what part of the rear end I broke...cheers

 

[ALLKHEINZ]

my 2010 ran 9.4 at 150, made near 900 wheel on a dynojet, went to the track every weekend of its life almost and as mentioned previously it had 100% stock 31 Spline Axels, 100% stock Diff with the carbon clutches, it broke 2 motive f888390 gear sets before i went to the stronger f988390...i just pulled a basically new Torsen out of my 2014 to go with the regular diff with carbon clutches...so far have made approx 50 passes to date with several 1.4x 60's best of 1.45.....im a slick guy dont believe in a drag radial on a stick car, for me its slicks or nothing...ive got drag radials on my auto 2015 they work well...9.60 at 143 with 1.37 best 60'....my opinion put in a stock diff with carbon clutches a set of motive 390 gears f988390 and call it a day. cheers

 

[Softballer77]

hate to be the bearer of bad news BUT the f888390 will last a little while but you will break them.....after myself, paul mitchell and a few of the BPS clan broke several sets i personally put a call into Motive...was told that with the weight and power the cars we had the gears in that they would break and suprised i got that much time out of them....they said go with the f988390 which were stronger rated for higher HP and weight....went that route never had an issue again.

Yeah...i was noticing there are 2 different types. However, the better set seems to whine worse than the set I had from what I was reading. Idk...my current set whined as it is. I can't imagine it being worse. If I find the ring broke, I'm just gonna pull it and reinstall my FRPP 4.10s for now. They were a good set. I just didn't like going through the traps right at 7k with them...

 

[Cman01]

Re: Cman01

Ring and Pinion is part of the Rear End is it not? so i did say what i meant, before you jump the gun it might be a good idea to find out what part of the rear end I broke...cheers

A connecting rod is part of the engine and if you put a rod thru the block the motor let go, your axles are part of the rear end and if you snap the axle your rear end let go also so you weren't specific as to actually what let go until you found out exactly after opening it up.

You said it yourself in your first post in the Local MB "The Stock GT500 Rear End finally let go................" I didn't know a Motive 3:90 gear was a stock item on a 2010 Shelby and it isn't my job to find out what part it is you murdered in your car on your track excursions. Had you updated that post with the info that your ring and pinion was the part that kicked it then we wouldn't need to discuss exactly what went south. To the majority of people if you say "your rear end let go" it usually means diff unless you specifically say it was the gear or axle that got trashed.

Anyways, I'm just busting your chops for amusement.................no harm no foul. As you know Sat. was a shitty day with major rain in the city and I was bored chilling at home not in the mood to drive the cars. I hope the FRPP 3:73's work out for you in the 14 car, as it looks like the motive 888 gear is made overseas and for sure is not as strong as the 988 gear for heavy drag duty. For what I do with my car the US Gear 3:90 that I have on order should work fine for my purpose.

Later Heenz.

 

[JB_2010GT500]

Okay I did a little more research. This post is to talk strictly about the 33 spline Wavetrac versus the 35 spline Strange S-Trac. The 31 spline Wavetrac is NOT built in the same manner, since it has C-clips to retain the axles.

The Wavetrac and the S-Trac use the same material and number of worm gears internally inside the case. So in this area they're structurally very similar. Now between the axle gears the Wavetrac has the additional locking feature of its design or as they say their "patented device" that sits between each axle gear to over come a single wheel no traction condition.

Both differentials are of a torque biasing gear designs. Now the Wavetrac can be disassembled to modify its torque bias, whereas the S-trac from what I can find any information about this can't

Now what does torque bias mean in this application.

These rears are built to sense a difference in available traction at each tire and use a torque bias ratio to determine which tire gets the most power from the engine. Typically this bias ratio is 2.5 to 1, or 2.5:1

This means if the wheel with the least amount of grip can handle 400 lb-ft of torque that the wheel with the most traction will receive 1000 lb-ft of torque. Now most of you are looking at the difference and thinking oh WOW, that equals 1400 lb-ft of torque, so each axle will spin at the same speed as I proceed down the track, because my engine is only producing 1000 lb-ft of torque at its peak.

Every gear from the engine to the tire is a multiplier of torque

Transmission first gear is a 2.66:1 ratio

Rear axle ring and pinion is a 3.73:1 ration

1000 lb-ft of peak engine torque is going to be multiplied by each of this different gear ratios

1000 lb-ft of peak engine torque x 2.66:1 first gear x 3.73:1 rear axle gear ratio equals 9921.8 lb-ft of torque being applied to the tires.

Now any torque biasing differential will stay locked and turn both axles at the exact same speed, if and only if each tire can support applying 4960.9 lb-ft of torque to the pavement in this example.


Now here is where the problem arises with a torque biasing differential. If lets say one tire can only support 2500 lb-ft of torque, the differential then comes into play to split it with a torque bias to maintain the same axle speeds. Again lets use a 2.5:1 torque bias ratio in the differential center section. So we have a tire that can only handle 2500 lb-ft with a torque bias of 2.5:1. This means that the other tire must have a capability to handle 6250 lb-ft of torque at the tire. Okay, so we add 2500 lb-ft + 6250 lb-ft = 8750 lb-ft. This is what the total will be of the total torque of grip the 2 tires can handle to maintain the same axle speeds. Unfortunately this does exceed our earlier math equation of engine torque x first gear ratio and rear axle ratio equaling 9921.8 lb-ft.......so both tires aren't going to maintain the same speed as the differential splits the torque. The axles will not be turning the same speed as the differential splits the torque. Both axles will be receiving power, but it isn't an equal amount of power and an axle speed differential will come into play as the one tire loses grip.

Now for the good news, I doubt any track you're racing at would have that significant of a difference in available traction or surface grip from the left to right tire in any situation, unless you're driving in your own fluids leaking from your car at the moment.

Now where is the Wavetrac different in this type of situation. Is it not only is torque biasing, it has their "patented device" between the axle gears to lock the two axles at the same speed once one of the tires losses traction beyond the point of the limits of lb-ft of grip available to a particular tire. So in our earlier example where a Tosen, TruTrac or S-Trac would have had a difference in axle speeds, the Wavetrac won't. Now that doesn't mean it will grip the track any better. Why? Because in the first math equation we have 9921.8 lb-ft of torque being applied to the tires. In the second math equation we showed an available grip of 8750 lb-ft. So we are now spinning both tires, only at equal speeds. Whereas with the other torque biasing differentials there will be a difference in axle speeds.

Now lets say the track does have significant difference in grip between the left and right tires and the total of that grip can handle 10,000 lb-ft of torque. Which differential has the advantage? Now we have more total grip than our engine output, but we have a significant difference in the left to right side. To me this really isn't a good situation no matter which rear differential you have, including a spool. Why? Because the car is going to try to turn in the direction of the wheel with the least amount of grip regardless of the differential in the rear axle.

I like the idea of the 33 spline axle Wavetrac in a street driven car, because of the fact it is not only torque biasing. It is also going to lock up under situation where a tire has zero grip. Now they also come with a life time warranty. They also can be taken apart and serviced. They can also be taken apart to change the torque bias ratio to your preferences. If you want a 4.0:1 torque bias versus a 2.5:1 this can be changed in a Wavetrac

All the others are exactly that torque biasing. What does this mean. This means if for any reason a tire has 0 lb-ft of torque application to the ground surface that is the tire that will get 100% of all of the available torque from the engine. Why? Lets says the differential has the standard torque bias of 2.5:1

2.5 x 0 = what?

ZERO!

All of the power is going to go to the tire that has zero traction. This is exactly what happens with an open or non-posi differential.

Now the Strange S-trac has an advantage in axle size. Why? It is 35 spline axle versus 33 spline axle. To add the 2 extra splines to the axle, the diameter of the axle was increased in size. As the axle diameter increased, so did the axles strength to handle torque. Now the disadvantage to this is the larger diameter axle is they weigh more. This is more rotating mass to get moving on the start. It is more mass to stop, but it is also more unsprung weight if you're thinking more along the lines of a car that you want to handle on a road course versus a straight line car on the drag strip. Now can you buy a 35 spline light weight axle? I'm sure you can, but it will probably be for drag race only applications. It won't have the capabilities to be used in a street/strip application where potholes or other hard knocks of street driving can bend or break the light weight 35 spline drag race axle.

There are advantages and disadvantages to everything. You have to decide which suits your needs better.

BIRDDOC was going to run a 9" 35 spline Wavetrac for Drag Week, but he changed to a spool. Why? He felt the Wavetrac wasn't capable of handling the torque his car produced for the days he would be at the track versus the advantages of driving the car on the street between each track event the Wavetrac would give him. So he felt that the extra effort required to steer the car and the fact it would chew tires up for the 1000 miles of driving was worth the extra strength a spool would net him to launch the car without fear of breaking rear axle components.

Everybody has to weigh these options and decide what works best for their situation and final use of the car.

Thanks for the detailed writeup, Kurt! Very informative and easy to follow. I'll tell you--you missed your calling. As someone who went thru five years of engineering school (and had to read thru many horribly-written texts), I think you could've easily been a top publisher of engineering textbooks, LOL! Thanks again!

 

[Bad Company]

Thanks for the detailed writeup, Kurt! Very informative and easy to follow. I'll tell you--you missed your calling. As someone who went thru five years of engineering school (and had to read thru many horribly-written texts), I think you could've easily been a top publisher of engineering textbooks, LOL! Thanks again!

You're welcome

Unfortunately for me you're not the first person to say this about me. I'm more of a hands on person and would rather work outdoors on anything mechanical than sit at a desk. Others have said I should have gone to school to be a teacher for mechanical engineering, because I lay it out in simplistic terms for other to easily understand.

As I've aged and with that supposedly gotten wiser(not LOL), I should have gone to on to become a mechanical engineer working with cars. I would have enjoyed that immensely

Thanks again for the kind words

 

[Softballer77]

300 miles and 1.5 launches...

 

[Bad Company]

View attachment 74250View attachment 74251

300 miles and 1.5 launches...

I was afraid that is what you were going to show. The 31 spline C-clip axles make for building the center worm gears shorter in length to accommodate the axle retention system. Unfortunately this makes for less overall strength.

Upgrade to the 33 spline when you ask for a warranty repair on this Wavetrac and pay the cost difference between the 2 of them. .

 

[Softballer77]

I was afraid that is what you were going to show. The 31 spline C-clip axles make for building the center worm gears shorter in length to accommodate the axle retention system. Unfortunately this makes for less overall strength.

Upgrade to the 33 spline when you ask for a warranty repair on this Wavetrac and pay the cost difference between the 2 of them. .

If we can get it out, we just may do that. So far, it's slammed in there. The passenger side C-clip is destroyed. The driverside is ok but it's jammed so bad that it can't be pulled out. Having to pull the entire rear end and taking it to a shop in Orange County. I have been in talks with Wavetrac via email. So far seems things are going to be handled ok. I have to call them tomorrow though. Huge pain in my rear (literally)...

 

[Beercules]

How much weight difference is there? I forgot to weigh the 9" axle before the install. I know the 9" diff is heavier, but the axle carrier is lighter.

One thing about the 9", one of the features that makes it stronger/quieter (the lower offset between ring/pinion) is also supposed to take more power to turn. My fuel economy didn't change with the axle swap.

You'll have to speak with strange/currie about gun drilling axles and strength. I know the outer sections of rotating elements carry the load, not the center... so gun drilling shouldn't weaken it much. But if a 35 spline does break, it will be bolted in at the wheel end instead of held with a c-clip, so it's safer.

LOL

Thanks J

Sometimes I think as I've gotten older that I should have paid a lot more attention in my high school trigonometry classes and been motivated to college to become a mechanical engineer. Than applied that to the love of playing with cars and guns. Especially after field stripping a high end custom pistol this morning and finding a cracked slide.

I doubt at your power level you'll break anything with the 33 spline combo. What I saw when I tore my rear apart is the carrier shims and carrier bearing pre-load is a major issue with the 8.8. None of the aftermarket shim kits work to pre-load the carrier bearings properly. You must purchase the Ford solid one piece shim oversized by 0.006" and drive it into place. Otherwise the carrier is going to move and change both the gear wear pattern and backlash. There is no other way to install the carrier and pre-load the carrier bearings properly in my opinion.

Unfortunately Strange doesn't start gun drilling axles, until you go to a 40 spline axle. Again they're looking at the fact they have to increase diameter to be able to add the extra splines. As diameter increases so does strength. So this allows them to gun drill the axle without loosing structural integrity. To gun drill the 35 spline axlemay be asking to break it easily. Also looking at Strange's website the 40 spline gun drilled axles are strictly meant for drag race applications with a different alloy

The 9" is tough and can handle a bunch of power without any issues. The down side is the added weight

 

[Softballer77]

I know it's been a while since this happened, but I wanted to make sure everything was fully worked out before posting.

GTR was unable to get the diff out, so Wavetrac advised to remove the entire rearend assembly to be taken to their trusted shop in Anaheim called Unitrax. GTR removed it, Unitrax picked it up. Sat at their shop a couple days. Turns out it took a cutting torch to get the Wavetrac out, not to mention my Moser axles were destroyed in the process.

Unitrax said it looked like the 3.90 ring and pinion wasn't set up properly, but they didn't say what the issue was. It wasn't what destroyed the Wavetrac though. The Wavetrac was sent to Wavetrac for inspection to find out what happened. They said it was such a mess that they couldn't tell what happened. As they said, "it's like a chicken/egg ordeal".

Wavetrac recommended I allow the rear assembly to be sent to Currie to be built. After some negotiation on what would happen and who would take care of what financially, it did go to Currie. New 33 splined Wavetrac, 33 splined Mosers, new 3.90 ring and pinion (Coincidentally, Currie said they install Motive in all their rearends) and new 9" ends welded on. They set up and installed everything, then it went back to GTR for them to install it back into the car.

All of this took about a month which i thought was rediculous, but was what it was. I have to say that even though I kept constant pressure on Wavetrac in regards to getting this done and taking care of things that was a result of the failure, they kept their composure the whole time and went above and beyond in fixing the situation. I did have to spend some money overall in the end, but I just sucked it up.

Wavetrac took care of:

Unitrax removing the diff
9" ends
Upgraded 33 splined Wavetrac at no extra cost
New 33 splined mosers
All new bearings
Set up of the gears
Installation of everything else (brakes, etc)

I paid for the new 3.90s since there was a "chance" they weren't set up correctly as they said. Just wanted to be fair. Also I agreed to pay the labor for welding the new ends. Of course, I paid GTR to remove and replace the assembly. So, like I said I wasn't untouched financially. Actually it still cost me about $1500 overall including a tow, but usually companies only cover their part that is warranted. Nothing else, and especially no labor. Wavetrac did me that favor. I think the power of the internet and forum participation makes companies realize the worth of keeping customers happy. So, like I said...to me they went above and beyond. Not to mention made it actually a pleasurable experience to work with them. On top of that, Currie did a great job. Good communication, etc.

I've put about 200 miles on it and my first impression is how smooth everything is. Quiet as well. I can't hear a thing but we all know this can change after a day at the drags. I will continue to update this post as those days happen, if there are any left before the end of the season.

 

[biminiLX]

Great update, glad to hear it's fixed and quiet. I really hope you can hammer it at the strip and it stays quiet.
I'm in a similar situation, my built 33-spline 8.8 was quiet cruising home and around town. The oil pump gears died datalogging it the exact same day I picked up the car from Team Z, so currently we both have quiet built rears that haven't been to the strip.
I don't know about you, but if this double braced rear doesn't stay quiet, I'm done with the 8.8
Didn't read the whole post, but what UCA do you run?
-J

 

[Softballer77]

It's all BMR back there.

You don't know how close I was to just doing a 9". Having just paid $1082 for a new CF driveshaft kept me from doing it. I didn't want to have to buy another one for the 9" already.