Hey fellas I have a question about upgrading my rear differential. Iam currently in the middle of swapping my FD's 13-b with an LS1 . With the engine mods we are planning to get 400+ rwhp and 400+ torque. The question is simple, can my differential hold up to that amount of torque?

Ive done multiple searches and It seems I get mixed answers. Some places on this forum say its good to 500+ torque. Others say over 300+ you "DEFINITELY" need the supporting mods I.E., upgraded bushing, diff brace, tranny brace etc. Which is it?

As far as suspension goes I only have aftermarket shocks. I only plan on taking it to the track a couple (literally) times a year and I occasionally bite down on it in the street.

Any input, horror stories, suggestions would be greatly appreciated.

Nelson

 

If you aren't going to use a "drag racing" tire, then you should be fine with the stock diff. However, if or when you want to "hook up" a launch at the drag strip with some sticky tires, you'll eventually tear up the stock diff. Many people have switched to the TII diff without much hassle.

 

go to www.v8rx7forums.com and search... If you ask a question like that your going to get flamed... surprised no one flamed you here as well... search is your friend.

 

Flamed huh? Now why should I get flamed? Ive been a member here as an FD owner when it had a ROTARY.

Somebody correct me if Iam wrong but its "RX7CLUB" not "ROTARYCLUB".

I OWN a 94 RX7 and have for over 3 years. Who has the right to flame me for a question that anybody with 400+ torque can answer (presumably).

And for those "Purists", you can only call yourself a purist if youre car is bone stock. How many of your cars are bone stock huh? Whats that you say? You have aftermarket turbos or any other mod? Well, go look on that manufactures website or on turbo specific forums. No my friend, as soon as you have modded your FD its officially been changed. Does the rotary make an FD what it is? Or is it the sequetial twins? Is it the lighter weight? Or is it its sleek design? Turbo, engine, bodykit or added components all change our FD into something else. So If I buy a vette and put a 13b in there, is it safe to say I can post on this forum asking questions??? Apparently this is a rotary forum...who would have thought.

Anyway, back to the real world. I did search and if you want to search to prove me wrong, do so. You will find mixed reviews. I am simply trying to clarify from multiple people the agreed upon torque limitations of the stock rear. Since I found multiple different answers I felt I should ask instead of guessing somwhere between 300-600.

Thanks



This is not within the spirit of my question but I felt it needed to be mentioned.

 

He was not saying you were going to get flamed for the V8 swap. He was saying you are going to get flamed for asking a question that has been asked and answered repeated times. You will continue to get mixed opinions, there is no 'magic' number.

I would wait until you blow the stock diff and then go with a Cobra rear end. I also agree with Mahjik, it's not totally about the torque number, but how good your car puts the power to the ground.

 

Thanks for the responses. That seems, oddly enough like a good suggestions As in, It should hold but, as with all things, it might brake. Therefore ride it out. My mechanic said it looked solid enough and from his experience it should hold. I just wanted to double check with you guys.

Thanks

Nelson

 

Basically, with drag tires, you can break the stock diff with a rotary engine fairly easily around 330 - 360rwhp. Once you address that, the axles are the next weak point which can snap as well at the same power rating. It all comes down to how that power is getting to the ground. With street tires, you'll have wheel spin to absorb the driveline shock. With drag tires, there is no real tire spin so your mechanical components take the shock.

 

Thanks Mahjik,

I guess its safe to say that one good grab could make me a sad person. I will be running nitto tires. The ones Iam picking up are the closest to radials while still being street legal. I guess I should start planning for a new differential.....

 

Also try and get rid of as much "Slop" in the rear end as possible, wheel hope has long been suspected as tearing up Differentials, getting new Pillow *****, and getting new Bushings has removed 90% of the slop I had before, and made the car much more solid in the rear... that being said the only time I launch hard is on the (road course track) and then just to get going to match the speed of the traffic on the track. I currently put down about 300 tq. according to my latest dyno. These days I get 0 wheel hop, it either grips, or looses traction, which can be scary going into a turn with some power
-DC

 

Easy buddy... I'm doing the LS1 swap well and know what diff to run and about where each one starts to let go. I know this through research and made an educated decision based on my research for my application. Not just asking a retarded question that has been asked 1,000,000 times without making a decent attempt to find out on my own.



good luck.

 

Here:

 

Well thank you for the colorfull pictures. I didnt know v8rx7forum existed to be honest which was why I was annoyed in the first place. How is it that I never heard of it? Who knows because neither grannyspeed nor jags that run mentioned it to me and they are basically who Iam getting all of the parts for the swap. Now that I look for it I see it everywhere.

Now, you posted some threads. Sure, I read some of those. We also must have typed in different things. I typed in rear differential, differential, ls1 differential, swap ls1 differential on different occasions. Most of the threads had NOTHING to do with how much it holds more so on how to replace X or Y or if they had a noise and people said it was the differential. Point being, I wanted one thread that contrasted what one person said to the other so we could get a consensus (if possible) on how much torque it would hold. I felt that in my REASEARCH there was too much of a gap with 2 many variables between said numbers. I understand why as Mahjik explained to me. Still I thought that If I asked specifically enough I might get answers a bit more specific.

Happy? You are there reason why some people are discouraged from asking questions. Theres only some many threads people are willing to skim through before posting a question. I get to page 3 then re input my search. If that dosent work then I quit and ask. Iam sorry this is not good enough for you and I apologize for asking my stupid redundant question.

 

You might look into the JimLab Cobra diff set-up that's popular with the V8 guys. Gear ratios better suited to your motor as well.

 

You already answered your question. Keep it until it breaks, and then upgrade. It may break in 6 month and it may make it 6 years.

If money isn't an object, go for the cobra diff right off, it is stonger and as stated has better ratios for the LSx engines. Also this way you could sell the stock FD setup, and recoup some of your expenses.

 

not trying to discourage anyone... I'm trying to encourage you and other people to look diligently because the answers are out there.

During your swap your going to find there really is no guide to do it and your going to have to research a TON... v8rx7forum is working on a "how to" book rightnow.

That being said, if you not running slicks or drag radials you should be fine on the stock FD torsion for some time. The most common "budget" upgrade I have seen is using the TII internals in the FD carrier... S4 (87-88) clutch pack style are considered the strongest by many, rebuildable and have been used for consistent low 10's without issue, I believe someone was pulling 1.3 60ft with one before it let go. The 89-on TII are V-LSD and quite strong as well. Other then that I would look into OS Giken, I consider them them best option with the stock carrier. Next option is going to a cobra IRS or solid axel there is tons of info on the V8RXfourm about it and different set-ups... All depends what your looking to do... 1/4 mile, street/strip, drift ect.

Good luck with your build.

Also I have hear terrible things about jimlab watch out.

 

Yeah, watch out.

 

I'm no longer making kits. Justin Samberg (www.v8rx7forum.com in the vendor section) now makes an IRS cradle kit based off my design.

 

I'm sorry I had you confused with someone else.... I was tired.

seriously... I'm sorry.

What was the company that was taking a retarded amount of time to get out the FD parts? all that went down when I was first going on to V8rx7forum

 

Dynotested/Acclaim Enterprises...

http://www.v8rx7forum.com/acclaim-en...ynotested-com/