Dual-Hump Crossmembers

[ssn696]

Both Jegs and Summit warn us that collapsed body bushings may cause their crossmembers to not fit under the floorboard. I have now purchased both and can prove this is true. However, in the side-by-side comparison, it looks like the Jegs version offers a bigger chance of conflict. (Jegs on top, looking towards the center from the passenger side.)

On the other hand, the Jegs design enables me to bolt it on under the frame extension, so it is at least holding the trans off the ground for now. No-go on the beefier Summit unit.

Both TH400/2004R models required the frame extension, adding $50-60 to the swap. I made my own from a scrap of 1-1/2 x 2-1/2 tube I picked up at the local Metal Supermarket for a few bucks.

I vote for the Summit version even though it is about twice the cost of the Jegs. Except I need to get those body bushings dealt with before I can mount the exhaust. Might be time to deal with the one rotten bolt plate in the wheel well...

I gambled that the cheap one was the better deal, and then I bought BOTH of them.

 

[motorheadmike]

The G-Force/Summit unit leaves a lot more room for full sized cats too. However, the Jegs unit isn't as over-engineered and weighs less I am sure. When I build the one for the wagon's 4L80E swap it is going to look like the Summit one, just 50% thinner... because it doesn't need to be that bloody big.

 

[timo22]

Quinn, I bought a used jegs 350 double hump off someone on this forum. Then I read some reviews and most guys said stay away from them. Well before I pulled my drivetrain in the Bonneville , I removed the stock one and slipped the jegs in. I had about 3/8" clearance from the floorpan. Guess my bushings are ok?
Tim

 

[ssn696]

I was kinda bummed when I opened the box with the TH400/200-4R model. The Jegs TH350 and 700-R4 models of yore were made from bigger tubing. I had to buy both for the coupe when the TH350 model ran into the tailhousing on the TKO600. Still had to trim down an edge, but chose the $129 part over trimming the $1800 part...

 

[timo22]

I had an iceman for my Malibu 700r4. Didn't like it at all. Seemed weak and shimmed the mount. It also felt like it bounced around tapping the floorpan on the rebound. Put the stock one back in for now. It feels a lot more solid.
I'll probably upgrade eventually.

 

[383_GrandPrix]

I was kinda bummed when I opened the box with the TH400/200-4R model. The Jegs TH350 and 700-R4 models of yore were made from bigger tubing. I had to buy both for the coupe when the TH350 model ran into the tailhousing on the TKO600. Still had to trim down an edge, but chose the $129 part over trimming the $1800 part...
View attachment 80857 View attachment 80859 View attachment 80862

The two in the first image look exactly identical... You said that one is for a 700r4 an the other for a th400?

 

[ssn696]

Second post, first image: 700-R4 on the left, TH350 on the right. The slight kickout accommodates the trans mount being 2" further back on the 700R4.

 

[383_GrandPrix]

Second post, first image: 700-R4 on the left, TH350 on the right. The slight kickout accommodates the trans mount being 2" further back on the 700R4.

Ahhh, ok I see it now, that makes sense.

 

[ssn696]

Quinn, I bought a used jegs 350 double hump off someone on this forum. Then I read some reviews and most guys said stay away from them. Well before I pulled my drivetrain in the Bonneville , I removed the stock one and slipped the jegs in. I had about 3/8" clearance from the floorpan. Guess my bushings are ok?
Tim

I did not have body clearance issues with the TH350 or 700R4 Jegs models, and the coupe sits on those almost-40-year-old bushings today. The wagon has been my source of grief, but I earned it choosing the 2004R...

 

[timo22]

I know the feeling. The joys of upgrades!