help welding rear crossmember

josbeat

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OK!
I am looking if someone knows on how to weld the rear subframe or rear crossmember to the chassis and if is possible to do it??
I been looking the crossmember claerance with the chassis and I dont know if it will touch the frame just in the midle of the laterals.

I am building an ultimate race track Supra Mk3 legal fo public roads anyway! so I dont care about noises ok?




 

LordDigital

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Hey man

What is the point of welding as opposite to using solid spacers? I have cut true 2 chassis in this area (junk cars that I used for parts and study) and trust me there is a solid reason why the subframe mounts with these super strong bolts! IMO the only way to weld it will be to extend your cage and weld to the rear subFrame on 4 points.

The real benefit will be to modify the rear subframe ,so that the car can be lowered from the subframe and not from the coilovers - this will help keep the rear geometry happy and reduce the bumpSteer. A mod like that is know to be doable on the MK4 chassis but I could not figure out an easy way to do it on the MK3.
 

josbeat

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Hey man

What is the point of welding as opposite to using solid spacers? I have cut true 2 chassis in this area (junk cars that I used for parts and study) and trust me there is a solid reason why the subframe mounts with these super strong bolts! IMO the only way to weld it will be to extend your cage and weld to the rear subFrame on 4 points.

The real benefit will be to modify the rear subframe ,so that the car can be lowered from the subframe and not from the coilovers - this will help keep the rear geometry happy and reduce the bumpSteer. A mod like that is know to be doable on the MK4 chassis but I could not figure out an easy way to do it on the MK3.
Hi!
that it is! i want to lower the rear of the car keeping the suspension geometry as ideal as possible.

I have the solution at the front but not for the rear with out weldding the rear subframe

I want to keep the bolts and the lower plates but I want to remove the top bushings (spacers) to get better suspension geometry , the driveshaft angles and the propeler shaft straight, also the sway bar will work better ....

do you know if is possible?

and at the last time if is necesary I think I can mount the rear diff with bushings to reduce the transmision strees eh?
 

LordDigital

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Hi!
that it is! i want to lower the rear of the car keeping the suspension geometry as ideal as possible.

I have the solution at the front but not for the rear with out weldding the rear subframe

I want to keep the bolts and the lower plates but I want to remove the top bushings (spacers) to get better suspension geometry , the driveshaft angles and the propeler shaft straight, also the sway bar will work better ....

do you know if is possible?

and at the last time if is necesary I think I can mount the rear diff with bushings to reduce the transmision strees eh?
Back in the days when I've done my subFrame build ,I looked into the possibility of lifting the sub-frame to reduce bumpsteer. My opinion at the time was that there is no way to do this for my goal of a 40mm (nearly 2 inches) ,less than that was simply not worthy the effort. Keep in mind tough that my assessment could've been inaccurate because here at my shop I do not have a full size chassis stand which is a common shop tool in EU and for some reason not common at all in the US. If you find a way to connect your sub-frame to your cage ,I'm sure that you can lift it with as much as you want and while you are doing this get rid of the POS MA70 sub-frame and upgrade to JZA80 which is much lighter and many times stronger with the added benefit of a wider track! The problem is that amount of work to do this will probably me more than simply fabricating replicas of the TRD/TTE Toyota Race hubs called "reinforcement knuckles" in the FIA/JAF SUPRA MA70 MK3 Homologation Book ;)

I know that you are trying to keep you transmission stress free ,and I would do the same if I spend that much money on a dogBox sequential tranny! Keep in mind that the rear subframes on our cars are one of the worst chassis components. It all starts with the fact that If you go back to the begging and mid 80's you will find that the computation power was very weak ... that means that CAD design for our cars was probably not used or used very little - as a result the MA70 rear sub-frame is simply BAD DESIGN ,and when combined with Toyota's poor implementation lead to a lot of failures. My effort to ensure that I have a sub-frame that can withstand standstill time attack starts on 275+ slick can be seen HERE ,but basically it involved welding 5+kilos of metal. Since for most of the failures the owners reported differential to be partially or fully loose ,IMO if you add bushings to the diff you will have a lot of problems with the subframe integrity ,not to mention the fact that they will induce tons of wheelHop (keep in mind that the JZA80 diff bushings delete which is very common mods on these cars).

BTW do you have any info from Quaife on the duty cycles of the QBE69G? IIRC the HKS sequential transmissions have average of 500 race miles life and their failures rates are closely related to the amount of up shifts the tyranny can withstand at full load on slicks ,$20k for a 500 miles tranny may sound crazy but this is the fact... another interesting fact is that a long time ago I inquired with UK based ProDrive for a dogBox sequential tyranny for EVO that would not require a rebuild for a ONE season (~2000 race kilometers) ,they quoted me $100 000 which was twice the budged of whole the team!!
 

josbeat

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thats is the same question I did to Quaife , what is the life of the gearbox
they dont have any information about that because the dont needed to rebuild any of those gearbox at the moment , using it on a complette rally championchip and enduraces championchips
at the moment I been two times on a tracks and some traveling ( arround 1700 miles on a public roads ) with it and no differences escept the gearbox noise is lower than before
also I just fit an oil cooler with filter to the gearbox so Ihope to get a long life of it.

I am very happy with the gearbox , really happy and I know if in the future I will need to sell it , it will be very easy because the price , it is the most universal and cheapest race gearbox I found.
ofcourse if you want to buy one of those gearbox there ,you will need to pay close to the double than me, here in Europe , I paid 6000 eur but in Dollars will be arround 10000 USD with shipping cost and maybe plus Customs taxes , so for me it is not expensive but yes for you. I Understand.

here we have some parts and tools and there you have others, for example if I want to do a copy of a rear knukle like you`re saying here it will be expensive very expensive so....I prefer to see if is possible to weld the rear subframe
and also wellding the rear sub with the chassis , it will be stronger than now noo???
mine don`t have any crack at the moment ans also mines look like it have a reinforcement from factory because it have a double wall where supouse it tend to crack...but I am not sure if it is normal.

the idea of use a bushings on the differential is to reduce the noise and vibrations inside the cockpit
I am using the car every weekend and only 3 or 4 time inside the tracks.
next year I am planing to do the hole time attack competition here in Spain but I want to be competitive jejeje but maybe the car is not the problem jajajajaja