Crossmember bolts

[78C10BigTen]

So, say half of them are Ks (I don't know if the Cs use the spacers too) .

No they do not, ive had my crossmember and trans in and out of my truck so many times in the last 2 years (4 trannys later) i can do it sleeping. My C is just a bolt with 2 washers and a nut.

 

[78C10BigTen]

And also ive never seen the crossmember bolted underneith the frame...

 

[Craig 85]

And also ive never seen the crossmember bolted underneith the frame...

My '77 K5 had it below the frame. It too had a NP-203. I lifted that truck 6" so I installed the sleeves between the crossmember and the frame to angle the drivetrain down ward. IIRC Skyjacker recommended that when I did the lift.

My '85 is my first K30. I'm finding it's definitely different than the 1/2 and 3/4 tons I've had in the past.

 

[Blue Ox]

No they do not, ive had my crossmember and trans in and out of my truck so many times in the last 2 years (4 trannys later) i can do it sleeping. My C is just a bolt with 2 washers and a nut.

Good to know. I guess that probably has to do with the K truck X-member carrying the extra weight of the transfer case.

And both of my mid '80s Ks have the crossmember under the frame.

 

[Battlac40]

No manufacturer puts "extra" parts in a vehicle, especially not as a consideration in case the owner wants to modify it later. Here's some quick math. According to Jane Pauley and NBC who did the smear piece on the side saddle fuel tanks, GM made 5 million of these trucks. So, say half of them are Ks (I don't know if the Cs use the spacers too) but if they cost 10¢ each that turns in to $1,000,000 over the production run. GM isn't going to give up that kind of money unless there is a necessity. Kind of like those front support brackets on starters the dealer technicians throw away ("You don't need that.") because it cuts the time they can make on a job.

I've seen at least one other application where a similar system is used. On Caterpillar 3208 engines the injection pump is only locked in place by two bolts on the back of the pump. That mounting flange was often prone to cracking. CAT came out with a revised mounting system using longer bolts with a spacer and a higher torque specification to "increase bolt stretch and improve joint clamp loading."

As to the question of orientation, my truck has the collars below the crossmember like Craig 85's. To the best of my recollection that's the way it came from the factory, but the truck has also had about six transmissions in it, so anything is possible.

Good points I own an 81 and 76 both have flat crossmembers and when I got the 81 it had the spacers there (as above in the 85'). When I bought the truck it had a 4 1/2in skyjacker lift on i tbut was missing many pieces. So, my mechanic and I chaulked the spacer up to the previous owner and "flipped" it dropping my tailshaft and fitting my driveshaft much better.
On my 76 i just got the bolts are mismatched and there is no spacers. But the previous owner stuffed a th400 and 205 where the th350/203 was. Thought about how to remidy the situation on a stock height
Curious.. pieces of chevy? maybe it was econimical considering the multiple crossmember/trans/case options (wasent there also a factory 2in lift option?) for our trucks maybe it was "cheaper" to create one part # for all the bolts?

 

[CSFJ]

No they do not, ive had my crossmember and trans in and out of my truck so many times in the last 2 years (4 trannys later) i can do it sleeping. My C is just a bolt with 2 washers and a nut.

And your truck is a 2wd without a transfer case too.

 

[78C10BigTen]

And your truck is a 2wd without a transfer case too.

Yea but they questioned what a C had as opposed to the 4wd K.

 

[Blue Ox]

Curious.. pieces of chevy? maybe it was econimical considering the multiple crossmember/trans/case options (wasent there also a factory 2in lift option?) for our trucks maybe it was "cheaper" to create one part # for all the bolts?

Not sure I understand the question. Per my post and Post #11, the longer bolts and spacers were to increase bolt stretch and improve clamping. It was an engineering reason, not a logistical one.

 

[Battlac40]

Had not read that far yet, was thinking out loud. Thanks for the clarification.

 

[bucket]

And also ive never seen the crossmember bolted underneith the frame...

It's a 4x4 thing... You wouldn't understand.




Lol, just teasing

 

[roundhouse]

I am laying under my truck this afternoon after work contemplating on whether or not I am even going to paint the rest of the frame now or wait until I have my lift to pull the cab off with ease. If I decide to not finish fully painting the frame now, I am definitely going to hit the parts that need a little paint just for temporary protection.

As I am going crazy with a brillo pad I started to wonder why the bolts on my crossmember are longer than necessary... is this a factory thing or was it whatever was laying around when they put this crossmember in last? Also, notice in the picture how deep the serial number stamping is in the frame. Seems a little overzealous to me with the stamping, but what do I know?

You must be registered for see images attach

Odd

We can’t find a serial number in mine anywhere

 

[Frankenchevy]

Odd

We can’t find a serial number in mine anywhere

You don’t have any numbers punched into your main frame rails beneath the cab?

 

[roundhouse]

You don’t have any numbers punched into your main frame rails beneath the cab?

No

Where should they be ?

 

[Frankenchevy]

In the area I circled, but on the outside of the frame. That is the backside of my stamping.

You must be registered for see images attach

 

[idahovette]

I just sold a rolling 78K-20 chassis and the numbers were stamped on the top side of the passenger frame rail?? FWIW