I'm one to use existing holes and or points of fastening rather than a total redo. That said I have an aftermarket 32 Ford frame built for seemingly a 700 or later trans. It has a nice drop out cross member but does not reach Turbo 350. Now the question. Has anyone ever built a trans mount bracket that uses the 4 tail housing bolt's? If a 700 can hang by these four bolts why not a 350?
True considering I plan to come off original mounting point with a flat plate (think upside down cantilever) so it can reach rearward just a tad further than tail housing bolts to intersect with cross member.
It'll work Jim. I'm just throwing out the load against bolts at tail housing. Like I said if later longer heavier trans can do it so can a 350.
Well...the load on the bolts might be quite a bit different, depending on how you make the mount adapter. A sketch would clarify that.
Check out Paul Horton Welder Series I believe they have just what you are looking for. Part No 35010 and Pt No 35012
Check out Paul Horton Welder Series I believe they have just what you are looking for. Part No 35010 and Pt No 35012
My DD, OT, truck originally had a 700R4 transmission, and at 36K miles, it was dead on the side of the freeway in Redding, California; the 700R4 had bit the dust. My mother and Grandmother were on their way to Tyler, Texas for my college graduation, from Lynnwood, Washington (just outside of Seattle). Since it was an 82 truck, no one, not even the Chevrolet dealer in Redding, knew how to repair a 700R4. A local transmission shop backdated it to a TH350, and to connect the TH350 rear mount to where the 700R4 bolted to the cross-member, they made a 1/4" thick steel plate with 4 holes burned through it with an O/A torch; a real piece of work that I would up replacing. Also, GM paid 85% of the cost involved to swap the transmission out. I later made a different cross-member so the transmission mount bolted directly to it. But, the plate would probably still be in the truck if it did't just look like CRAP My Mother later gave the truck to me, after she spun the main bearings after running it out of oil! The drawing above, ^^^^^, is similar, just without the smaller brackets that attach to the transmission extension housing bolts. I am Butch/56sedandelivery.
This should shed some lite as to why I'm not fond of redoing attaching point of cross member mounts to frame per this tubular K member for which frame I'm working on has. I prefer to leave it alone.
@Johnny Gee The question about the load on the tail housing bolts neglects to take into consideration that the tailhousing has a ‘spigot’ (? terminology) that inserts in the the back of the trans case. My point being, the bolts carry very little of the load in shear because of the interlocking of the tailhousing to the case. The two bottom bolts are, IMO, adequate. An alternative to four bolts might be to add a small pad to the new mount bracket that bears against the bottom of the case/tailhousing joint to share or eliminate entirely the shear loads on the bolts. Not really necessary, but it’s a slow night...conducive to overthinking... Ray
To be honest when I started this thread the original idea was like that of the Hurst unit that Rich B posted but would be instead welded together as a single unit and was not going to connect to tail housing where trans mount normally goes. It changes consistently in my head "conductive to overthinking" as well. I'm just happy that the idea is being accepted rather than looked at as a hack job. Which is why I really thru this to the wolves.
I think that general idea (Hurst “style”) would be more than adequate. I looked again at your drawing and think it is more than needed, extending to the original pad mounting point, but no harm in that. I usually tend to overbuild, at least initially. I constantly look at professionally engineered parts/assemblies, trying to analyze and adopt the savvy to make better parts for myself. Usually, I am amazed at how much less an engineer thought was necessary than I did or would have. You have several good choices..... Ray
The revised drawing (erasers are great) will only use the two bottom bolts that hold tail housing to the main case. There's a reason Hurst used only 3 bolts. Tail housing won't accidentally separate . I'm just increasing my safety factor but still using 4 bolts. Or is the extra safety for someone else? I'll let you decide.
Personally I like what you have drawn up in your drawing in post 10. I'd put a gusset on it though. The only issue I see with that is that it will raise the back of the trans the thickness of the metal. You may have to step it (cut and overlap) behind the trans mount boss on the trans to get it down that thickness. The thing I like about using that setup is you aren't adding any stress to the drop out trans mount. Running a plate forward off of it would add a lot of twist stress. If you haven't got it, this chart shows most of the dimensions on GM automatics and shows the back of the block to center of trans mount boss measurement on each. https://www.monstertransmission.com/Automatic-Transmission-Dimensions-Measurements_b_84.html It may not be of any use this time but it might verify your thoughts on what trans it was intended for.
Not an issue. I know it's hard to till in post #16 put cross member is adjustable up and down. Yet another feature I wanted to take advantage of over redoing/moving/make new cross member and attaching points to frame.
I have a friend that builds to a very high standard (think Ridler, AMBR etc.)... on his current build, he too is using this same principle, but is mounting the trans from the top. So when viewed from underneath, the transmission looks like it just hangs from space with no crossmember.
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