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Thoughts on a rear end?


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#1 Gumby83

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Posted 20 April 2017 - 05:13 AM

I am wondering what rear end setup would allow me to support 700rwhp  and hard launches at the drag strip reliably... i hear so many different opinions from using a R230 and custom cv/axles to a corvette IRS Swap. I have no rear end as the car sits right now, and one of the lower control arms is buggered so all options are open to me. Suggestions?



#2 jacky4566

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Posted 20 April 2017 - 06:16 AM

If your doing a drag car i would suggest installing a solid axle. Its going to save alot of headache and even the wimpiest ones can support tons of power. 



#3 Gumby83

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Posted 20 April 2017 - 06:31 AM

Any popular swaps for the 240 as far as solid axle?



#4 Zfan1

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Posted 21 April 2017 - 03:23 AM

A narrowed 9" is probably overkill, maybe an 8.8" narrowed would be a good option. Plenty of those to be found.



#5 weedburner

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Posted 23 April 2017 - 12:14 PM

My RX-7 is similar to your car in size/weight/power. I went with a narrowed GM 8.5" 10 bolt solid axle and added a torque arm. If i were doing it again, i would go with a Ford 8.8 just because they are so much easier to find and about the same strength. With the torque arm setup you will need to fab some brackets to attach the lower control arms to the chassis, a panhard bar or watts link to center it, and an anchor bracket for the nose of the TA up in the tunnel. Not sure how big your stock wheelwells are, but my stock RX-7 wheelwells hold 28" tall 275/60-15 drag radials with very little room to spare. I have over 700hp to the wheels with a manual trans, here's a link to a page featuring my car... http://grannys.tripod.com/20102.html . 

 

Here's a pic of a similar setup that i added under a 2nd gen RX-7 to replace it's original IRS...

 

TASA6500w.jpg

 

The vertical bolt is actually the large stud that the original IRS subframe bolted to. In addition to the large stud that located the bracket, there are (4) 3/8" bolts in the bottom plate and (4) more 3/8" bolts that attach the bracket's backside to the chassis. Both sets of 4 bolts also have a 1/8" thick backup plates to spread the load on the inside of the car.

 

Here's what the overall set of brackets look like to convert an IRS 2nd gen RX-7 to a solid axle...

 

2TASAkit2500w.jpg

 

The torque arm does not weld to the axle housing, it simply slides over the pinion area and attaches thru a plate that fits over the lower section of it's rear cover. The two odd shaped brackets on either side of the torque arm are anchor points for the watts linkage, the one brachet with the stud is a pivot point for the watts linkage's bellcrank which welds to the right side axle tube. The (4) unpainted brackets weld onto the axle tubes to attach the lower control arms, as well as the shocks. This setup was designed to use the original lower control arms and watts linkage from a '79-'85 solid axle equipped RX-7 to keep cost down.

 

Here's a link to a page that shows converting the IRS second gen RX-7 to a solid axle... http://grannys.tripo...stallguide.html

 

I don't make anything for a hybrid Z, just thought the pictures might inspire someone

 

Grant



#6 weedburner

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Posted 23 April 2017 - 12:57 PM

Launching at the dragstrip reliably with a manual trans can be challenging, but most of the magic in getting it all to work reliably is getting the clutch to hit with just the right intensity. Too much clutch capacity can make the car tend to either spin, bog, or break. I came up with a device using a hydraulic screen door closer that allows me to easily adjust how hard my clutch hits. Without it, my car instantly twists it's driveshaft in two. With it, my car dead hooks and does 1.30 60's without bogging. My page on my car (linked in my post above) shows the cylinder installed and attached to the clutch pedal, it also shows the dash bracket. The RX-7 is similar to the 240 in that the distance from the dash to the pedal is fairly long, so you should be able to slightly modify an off-the-shelf Wright VH440 closer to do the same thing. I make a shortened version of that same cylinder, very popular with the stick shift NMRA guys.



#7 Gumby83

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Posted 26 April 2017 - 08:12 PM

My RX-7 is similar to your car in size/weight/power. I went with a narrowed GM 8.5" 10 bolt solid axle and added a torque arm. If i were doing it again, i would go with a Ford 8.8 just because they are so much easier to find and about the same strength. With the torque arm setup you will need to fab some brackets to attach the lower control arms to the chassis, a panhard bar or watts link to center it, and an anchor bracket for the nose of the TA up in the tunnel. Not sure how big your stock wheelwells are, but my stock RX-7 wheelwells hold 28" tall 275/60-15 drag radials with very little room to spare. I have over 700hp to the wheels with a manual trans, here's a link to a page featuring my car... http://grannys.tripod.com/20102.html . 

 

Here's a pic of a similar setup that i added under a 2nd gen RX-7 to replace it's original IRS...

 

TASA6500w.jpg

 

The vertical bolt is actually the large stud that the original IRS subframe bolted to. In addition to the large stud that located the bracket, there are (4) 3/8" bolts in the bottom plate and (4) more 3/8" bolts that attach the bracket's backside to the chassis. Both sets of 4 bolts also have a 1/8" thick backup plates to spread the load on the inside of the car.

 

Here's what the overall set of brackets look like to convert an IRS 2nd gen RX-7 to a solid axle...

 

2TASAkit2500w.jpg

 

The torque arm does not weld to the axle housing, it simply slides over the pinion area and attaches thru a plate that fits over the lower section of it's rear cover. The two odd shaped brackets on either side of the torque arm are anchor points for the watts linkage, the one brachet with the stud is a pivot point for the watts linkage's bellcrank which welds to the right side axle tube. The (4) unpainted brackets weld onto the axle tubes to attach the lower control arms, as well as the shocks. This setup was designed to use the original lower control arms and watts linkage from a '79-'85 solid axle equipped RX-7 to keep cost down.

 

Here's a link to a page that shows converting the IRS second gen RX-7 to a solid axle... http://grannys.tripo...stallguide.html

 

I don't make anything for a hybrid Z, just thought the pictures might inspire someone

 

Grant

 

Wow, that is a seriously impressive build!  Also, thank you for the information! cheers! 



#8 ZScott99

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Posted 08 May 2017 - 02:37 PM

https://zcardepot.co...racket-kit.html I would look into this. Ive done lots of reading into rear end options and this seems the most straight forward. 



#9 Neverdone

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Posted 08 May 2017 - 02:57 PM

Ordering those brackets still requires you to purchase 

 

1) Their rear end cover to mount them to

2) The diff itself

3) A custom driveshaft

4) Custom axles.

 

3&4 aren't offered by anyone, but you could go to a shop that builds axles and driveshafts and using proper measurements that you'd have to take yourself, give to them.

 

If anything, that's the LEAST straight forward option.

 

Meanwhile...https://technotoytun...onversion-z-car

 

They walk you through everything you'll need and nearly everything is included. It's sorta spendy, but if you're looking at high torque numbers, it's probably a good way to go short of straight axle install.



#10 Richard Oben

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Posted 10 May 2017 - 08:39 AM

Other opinion here.  I did not do the Z car depot thing, we built our own 8.8 set up.  I have some terrible pictures that I will post on a build thread at some point.  We did an 8.8 as we have a ton of experience with them, and we owned a great aluminum center unit from a Lincoln Mk8 3.73 positraction.   

We used the TTT, front mount and made our own rear mount, used 930 stub shaft adapters from the drive shaft shop for the inner and adapters from Z car depot for the outer to the Z drive flanges.  We had custom axles made for the 930 CVs and of course a custom drive shaft from the T56 to 8.8.  Currently has no miles on it but that will change soon.  

 

All in it was not terribly expensive to do but has its limitations.  In retrospect, going with an R200 and LSD would have been easier, but not as much fun.  Kind of like figuring this stuff out.  

 

Again, just my opinion.  For the kind of power you are going for a back half car will be the answer with a solid rear axle.  HTH, Richard. 






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