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Crossmember I.D.

S

SUB602

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OK guys i am getting ready to put my Blazer together, but i have a small problem. I have 3 different crossmembers. Which one goes in a 1975 Blazer?

The one pictured on top is from a 78. The one from the 78 has an oval hole and a round hole. You cant see them too good in the pics. The one in the middle and bottom both came in the back of the 75 when i bought it.


crossmember.jpg

crossmember.jpg
 
It depends on your transmission.

There are two factory crossmembers on mine, and they both look similar to the top two (I have a 465/205).

The bottom one looks like it went with a 208 I think.
 
On my 73 (350/203) the primary cross member looks like the left half of the bottom one on both sides (having the 2nd piece to tie to upper frame). The secondary cross member is just for the skid plate and looks more like the middle one, without the holes.

If I were you, I would use the bottom one, the added bracing makes it stronger
 
So your saying the bottom one actually bolts to the Transfer case adapter and the middle one just has the skid plate mounted to it?

You know that makes sense after taking another look at the crossmembers. The one on the bottom has the bushing imprints on it where the one in the middle does not.
 
I have a 203 crossmember still bolted to the th350/203 combo . I'll snap a pic when I get home .

The bottom one is a 70's crossmember for sure . The top one looks like my 83 .
 
Others have said this isn't true, but measure the spacing between the frame bolt holes side to side on either of the top two and the bottom one.

I couldn't get a crossmember from the 70's to fit my '81 frame, it was too wide as I recall.
 
None of those members were used on '81 and newer trucks. Those are all between '73 to '80.

The bottom one is the oldest one, being mounted in '73, '74 and some '75.
The other two were the other 70's years.

It wouldn't matter which member you use as long as you have the correct height of tranny/t-case adaptor. If you're planning to use one of these 3 members, make sure your adaptor is an '84 or older as the '85 and newer use the double-hump members.
 
Those top two look pretty similar to the one in the second picture shown here, which I took off an '81+ truck because a 70's crossmember wouldn't fit: http://dyeager535.topcities.com/frankentruckpics.html

How do you differentiate the top two as being pre-'81? I know there was a three piece skidplate setup earlier, looks like the ones in the original posters picture are setup to allow you to bolt that up to it?

Did the '81-84 208's bolt up to the crossmember like the 205 with the separate transmission mount pieces? Not one piece like the '85+?
 
'81 to '84 members look different than those shown in the pic above. I can't describe them without a pic. Maybe someone else can post one up if they have one off an actual '81 to '84 truck. Trust me, they're different. I believe where GM did some weight "shaving", they "removed" some material from the flatter part of the members where the skidplate holes are.
 
Absolutely correct, at home now could look at my '81-84 x-member. The lip on the edge is narrower except in a couple of spots where it bulges out.

Also use lightening cuts along the surface where the tranny mount bolts on further out near where the crossmember starts to curve up to the frame.
 
Well i am going to test fit them this weekend. Since the bottom 2 members came with the Blazer when i purchased it i will see if they fit. I just wasnt sure since they were not installed under the truck. Thanks for the help.
 
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I cant look at your pictures but I highly recommed running the second crossmember. When I got my blazer the knuckle head before me put the 203 behind my 700r4 and Only used the one crossmember the bolts onto the transmission/transfercase adpater. It was fine under use in 2wd but the np203 is so heavy and has so much weight hanging behind the adpator that it has to have that second crossmember to take some of the weight off. It was so heavy that my transfercase was literally jumping up and down so bad in 4wd that it ripped the bolts that bolt the tranny to transfercase out. I am told the factory brace(second) hooks onto the tranny further up but I have never seen one so Im not sure. I just fabbed one that hooks onto the frame rails and bolts into the 2 existing holes on the back passenger side of the transfercase. So far it has worked great and did wonders for my drivetrain slop. Ill try to post some pics put my memory card is stuck...lol maybe you lready know this and I look like an ass but I definately dont want anyone having the same issue I did.
 
No i appreciate your advice. If i can get a pic of someones 73-75 crossmembers intact. Pauly383 is working on that for me so that would pretty much answer my question. I am actually cleaning them up right now and i can see where the skid plate bolts to the second member. So i believe you are absolutly right. That both crossmembers need to be used. Thanks
 
Well , take the crossmember on the bottom , turn it around so the flat is on the drivers side , and it bolts into a 76 ... which is waht my th350/203 came out of .

The passenger side had that special mount between the frame and the case bolts on the side of the 203 .

100_1424.JPG
 
I've got the one out of a '76 Jimmy I can snap of pict of for you tonight. It had a 350/203 combo. It was the dual setup, one on the tranny and one on the tc with the skid plate connecting them. If I rember right, they were like the two rustier ones on the bottom of your first pict.
 
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