A-70 Rear Subframe reinforcement/strengthening

[HKS_TRD]

Well

with all the talk and discoveries of cracked rear subframes on A-70 Supras, and Soarers which share the same rear subframe, I've had a look at mine and after a brief "yay no cracks" I've decided I would like it to stay that way.

From what I can surmise, its the area around where the front diff bolts on to the subframe that cracks. What would be the best preventative measure against cracking in this area, welding in extra metal, or maybe even having a plate made up that goes between the subframe and the bolts?

Keen to hear everyones ideas.

I'm considering getting a spare subframe and strengthening it as I need my car to be able to be pushed around while its off the road etc, where are people getting them from anyway?

[Hybrid]

Thankfully mine appears to not be cracked, yet

[silver_ta22]

andrew at CVAP sold me one a month or two ago.

i had it sandblasted and its crack free. So i've painted it with some POR15 and will be swapping it in when i have the motivation!

I looked at getting it strengthened. The fabricator quoted a range from $1000 -> $1800, as he needed to build a jig to keep the mounting points from moving.

Didn't want to spend that much, so im happy enough with the subframe in good condition. And it will get new poly bushings and correctly torqued bolts when it goes in.

Looking at my original subframe the rubber bushings are in bad shape, and it would be moving around a lot on the bolts. I'd say this flex or movement would cause cracking. So if nothing else make sure everything is correctly tightened! So the diff can't move around on its mounts.

[HKS_TRD]

andrew at CVAP sold me one a month or two ago.

i had it sandblasted and its crack free. So i've painted it with some POR15 and will be swapping it in when i have the motivation!

I looked at getting it strengthened. The fabricator quoted a range from $1000 -> $1800, as he needed to build a jig to keep the mounting points from moving.

Didn't want to spend that much, so im happy enough with the subframe in good condition. And it will get new poly bushings and correctly torqued bolts when it goes in.

Looking at my original subframe the rubber bushings are in bad shape, and it would be moving around a lot on the bolts. I'd say this flex or movement would cause cracking. So if nothing else make sure everything is correctly tightened! So the diff can't move around on its mounts.

Bugger thats a fair whack for reinforcing the subframe.
If you dont mind me asking, how much was the good one you bought?

[ReQuieM]

I've been thinking about making a few bolt on cross braces to re-enforce it. Not in any real rush tho.

If you have a look at how the nuts are held on the frame you can see how the manufacturing process has compromised the strength. I think just additional welding and bracing around the mount points would make a worlds of difference.

As for jigging. If you were that worried about warping, leave the diff in while welding. I seriously doubt that you would get enough heat in the frame to warp it further then a localized area which the diff should hold in place, this with a TIG/MIG. Although the shop was probably covering its arse, Make a full jig to remove any doubt of movement and then for complaints, law suits etc etc, Which is fair.

[silver_ta22]

yeah he was an old school guy "got to do it the right way", not a mate with a welder or anything.

my bill so far on subframe is
good subframe $125
freight $100
sandblasting $150
poly subframe bushings $240
POR15 paint $110 (only used half though)

[ReQuieM]

Yup sounds like the kind of bloke I would take my stuff to if I was going to get someone else to the work. Costs more but you KNOW that your gettign a fkn good job

That sandblasting seams quite pricey, I thought sandblasting was cheaper then that? How come you didn't get it cemically cleaned instead? Less abrasive.

ALSO, be really vigourous with the application of the paint. I've heard of people havign things (like shells etc) professionally stripped, painting going about there business only to find the item has proceeded to rust from the inside out! Its obviously common sense to make sure you coat the inside to, but its surprising how often the 'obvious' is accidently over looked.


Got any piccies btw?

[silver_ta22]

have you seen thread on supraforums from a little while back? http://www.supraforums.com.au/forum/...light=subframe

yeah sandblasting was little pricey, chemical cleaning would of been harder to organise I'd say. sandblasting wasn't very abrasive, took off the old paint, didn't damage metal.

as for the insides i got most of it, but you've made me want to double check. it was a bit of a pain accessing everywhere!

[HKS_TRD]

Nice work there!

After all that you would be seriously hoping it doesnt crack.

[big JON]

I will be dropping my subframe in the coming weeks to drop it off to my uncle who is a fabricator / engineer type.

We're gonna have a chat and i'll show him the image Rob posted a while ago in the thread on sf.com.au and get him to do something similar, then when i get back from Mexico it will be ready for me to pick up and put back in

[jimmmayyy]

You'd be better off sandblasting, it will completely clean any possible rust spots and gives you a good profile for painting. Chemical cleaning can leave residue that makes it hard to paint. Plus it also oxidises the metal, which can cause it to rust under the paint, ie from the inside out like requiem mentioned.

[silver_ta22]

yeah i was happy with the result of sandblasting it, nice and smooth surface to paint.

[Draven]

maybe try asking linden about this.. (therealroadrunner on these forums)

I'm sure he has a few g-series A70 rear ends lying around, and if there's interest he could probably be convinced to do a run of them.
He does farkin nice work too

[HKS_TRD]

maybe try asking linden about this.. (therealroadrunner on these forums)

I'm sure he has a few g-series A70 rear ends lying around, and if there's interest he could probably be convinced to do a run of them.
He does farkin nice work too

You talking about bracing one or making one from scratch?