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Discussion Starter #1
Hey everybody, long time lurker, first time caller.

Once I find the right place on the forum, I'll start documenting the full drama of the rebuilding of the Purple Impala, but for now, I have a planning quandary of the transmission variety.

I've got a 1968 Impala Custom Coupe that I'm building back up from the frame as a daily driver, and she's destined for a good deal of highway miles - hence my desire to go to an Overdrive Tranny. (Which will be bolted to a 355 Gen I SBC; no LS Swap for me)

When I picked it up, the Previous Owner (PO) had given up on a 350 swap - so I had a seized 350 out of a 70's Corvette, and a B&M TH350 under the hood, with no drive-shaft leading to the 10 bolt 8.2 rear-end. From what I can tell of the records, the car had started as a TH400, but that's very sketchy/word of mouth info at this time.

The pictures below are of the tranny crossmember. The PO drilled (or chewed, see below) 2 holes in the mounting plate, and that's how the TH350 was bolted in.

So finally, here are my questions:

1) Can I get a 700R4 onto this crossmember? If it won't bolt in this direction, flipping the bar will move the mounting plate 3" to the rear of the car.
2) If I need to buy a new crossmember, do they make a flavor that bolts in to the same frame mount and supports a 700R4?

I've seen a ton of conflicting information on OD Tranny installation / guidance for the 4th Gen B-Bodies, If anyone has a definitive guide that I can look at, I'd appreciate it. Push comes to shove, I'm going to get the 700R4 and measure it out before I put the body back on, but I usually like to plan ahead.

Thanks in advance folks.

Photos

29707


29708
 

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You can definitely do a 700R4, and that is a great choice for what you are going to use the car for. Just slide the crossmember back on the frame and bolt it in place.
 

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Discussion Starter #3
... and by slide, you mean remove the welded supports for the cross member and re-weld to them further back in the frame?

Luckily, I also happen to have a little flu wire welder... I’d imagine I’d just use it for floor pans. Seems that it’s about to get more value if that’s what is needed to replace the tranny.
 

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Yes. Cut the brackets off and either weld them on the frame or simply fab new brackets and bolt them on.
 

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Just buy the correct cross member that fits a 700r4 no welding required..

.Google is your Friend...


They all sell them... classic industries, ecklers etc...



 

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Yes, but... sawzall blades, drill bits, and bolts are cheaper. Full disclosure: I have an aftermarket crossmember in my T56 car, lol
 

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Discussion Starter #8
Ah - actually the picture from the Ecklers site is a solid clue. Thanks.

I did Google other bars, but the photos were so awful it LOOKED like they would require welding anyway.

Thanks guys - I’ve got enough to do on this car that I’m juuuuuuuust fine buying my way out of this one!

Cheers!



Just buy the correct cross member that fits a 700r4 no welding required..

.Google is your Friend...


They all sell them... classic industries, ecklers etc...



 

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Registered
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1 Posts
Hey everybody, long time lurker, first time caller.

Once I find the right place on the forum, I'll start documenting the full drama of the rebuilding of the Purple Impala, but for now, I have a planning quandary of the transmission variety.

I've got a 1968 Impala Custom Coupe that I'm building back up from the frame as a daily driver, and she's destined for a good deal of highway miles - hence my desire to go to an Overdrive Tranny. (Which will be bolted to a 355 Gen I SBC; no LS Swap for me)

When I picked it up, the Previous Owner (PO) had given up on a 350 swap - so I had a seized 350 out of a 70's Corvette, and a B&M TH350 under the hood, with no drive-shaft leading to the 10 bolt 8.2 rear-end. From what I can tell of the records, the car had started as a TH400, but that's very sketchy/word of mouth info at this time.

The pictures below are of the tranny crossmember. The PO drilled (or chewed, see below) 2 holes in the mounting plate, and that's how the TH350 was bolted in.

So finally, here are my questions:

1) Can I get a 700R4 onto this crossmember? If it won't bolt in this direction, flipping the bar will move the mounting plate 3" to the rear of the car.
2) If I need to buy a new crossmember, do they make a flavor that bolts in to the same frame mount and supports a 700R4?

I've seen a ton of conflicting information on OD Tranny installation / guidance for the 4th Gen B-Bodies, If anyone has a definitive guide that I can look at, I'd appreciate it. Push comes to shove, I'm going to get the 700R4 and measure it out before I put the body back on, but I usually like to plan ahead.

Thanks in advance folks.

Photos

View attachment 29707

View attachment 29708
I just made another set of identical chassis brackets and welded them on further back
 

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Depending on engine choice you can get by with a 200R4 because the case length is very close to a TH350. The OE crossmember lines up just right. The larger 700R4 is longer. BowTie Overdrives makes a very good product. I have installed a couple of them and their tech dept is top notch. They offer a kit to change the column or floor shifter so the shift positions are true. Here is an image from the Impala factory book showing the second crossmember mount location for the TH400 or the 700R4 brackets. I have a 200R4 in my own 66 Impala and my 283 runs so sweet.

29731
 

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Discussion Starter #14
Thanks for all the info and suggestions!

I ended up getting a really nice bar from Classic Chevy / Eckler.

29829


Well built, and nice looking. I'm leaving it to float while I work on the suspension, and I'll also do a dry-fit of the engine and transmission to make sure that it fits - I did see one fellow that used this bar that had a problem with the nose cone of their 700R4 - specifically the speedo gear. We'll see!!
 
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