Hi everyone,
i wanted to ask if someone has a JUN rear subframe on his FD? if yes then how comfortable is the car when driven on the street? would you recommend this for drag setup? what sort of Final Drive options do we have for the FD, cause the USDM is 4.1 and the Spirit R is 4.3. i think that's a bit short for a 4 rotor setup? what are my options for Final drives?

apologize for the multiple questions, but they are all related to the rear subframe

thanks

 

Buy a Ronin 8.8 rear end conversion and you can run any rear gear for an 8.8 you want, from 2.73 to 5.12.

 

was this been done before on an FD? i believe this is going to be custom work to the rear frame?

 

They make a kit. It has been done quite a few times. There is some welding needed but it is not much. The lowest rear gear you can get is a 3.90 for an FD. There is a 3.73 that works out of an MPV van I think.. but good luck finding that. With the 8.8 you can put in a better, cheaper differential and any gear ratio you want.


FD Ford 8.8 IRS - Complete Mount Kit w/ Axles

 

great ! thanks for the info! i know about the IRS setups, but that diff is huge....hehe

who offers the 3.9 FD you were talking about? is that the stock USDM FD Auto rear Final Drive? if i had a choice to do a custom seq gearbox would you leave the rear diff stock with an aftermarket LSD or upgrade the rear diff to an 8.8 IRS? i forgot to mention the tranny part as im not going to use the stock 5spd. thinking of using a T56 gearbox and as you know theres a lot of aftermarket products for that tranny. one of them is going either straight cut or even sequential which im considering. i do have a 4 banger with a dog box that i drive on the street and i know how a dog box feels. not to mention the rev matching part is fun to do....hehe

so which would you recommend and still be lowest in cost to reach my goal?:

Option 1:
* straight cut dogbox or seq gearbox (custom with longer gears)
* rear JUN subframe
* stock 4.1 or 3.9 FD
* aftermarket LSD

Option 2:
* straight cut dogbox or seq gearbox (custom with longer gears)
* custom IRS 8.8 with LSD and appropriate FD ratio

i know both both options are not considered to be cheap, but im trying to make notes of the part list to start getting for this project

 

Project purpose a fun car to drive on the street and still go to the drag strip occasionally. This is not a drift or circuit car, so im trying to keep it full interior

 

Yes the 3.9 is in the auto FDs.

If you want a fun street car, I would lean toward the 8.8. It is basically the same weight, much stronger, and you can get a diff better suited to what you want to do for much cheaper. It will probably keep your trans costs down because you wont really need "special" gears. You can build the trans and get the appropriate rear gear. I have a v8 in my car with a t56 and 3.73s in a 8.8.

 

thats really nice, but how well the LSD on those 8.8 are? i used to have a supra with a TRD LSD and man i loved it more than my friends z06 c6 stock rear diff.

whats your trap speed with that setup you have? im curious cause im a big fan of the T56 trannies. its very rare the gears break. its either the syncro or something else, but the gears are strong being stock

what engine setup are you running?

 

so you'd recommend a 5spd FD tranny with a 8.8 rear diff? dont you think a built 5spd FD stock tranny wont hold the extra power? i believe they are weak

 

I have an LS1 in my car. I road race it and don't drag it but it would trap in the mid-high 120s.

The stock Ford LSD is decent. There are many many aftermarket diff options. I have a Detroit Truetrac in my 8.8.