Need advice: LS ENGINE SWAP

[dman1982]

You know I'm waiting...you messing with me?

[wheresbrent]

Bump.

[desertdogg]

Well, I am back !. so after my last post on this thread everything came to a shrieking halt due to my dad getting sick and ended up passing away on August 12th 2014. Not too much longer after my dad passed away my Mom got sick and passed away two years later almost to the day of my dads passing on August 20th 2016 and my truck had not been touched the whole time, just sitting and collecting dust. I just had no drive to finish it, lost interest. Its now time ! I tried several times to just go work on it but it never got far. I figured one day would come and I would be all in with the same enthusiasm I had when I first started this project, I believe that time is here. I have been lurking around and reading my old posts and build thread and am very greatful to this site because of the valuable documentation I had put on here and now I know where I left off, and whats been done, its been a lifesaver on this build and so nice to be able to get back on here { after finally remembering my user name and password } and get started again and hopefully get this thing finished. Anyways I will be asking a lot of questions as before so hopefully I can get the same support from everyone that is willing to help. Feels good to be back

[ls1nova71]

Sorry to hear about your parents, that's rough. But good to see you back on the project.

[skyphix]

Welcome back - I've been in similar shoes to the ones you've been wearing and its not an enjoyable experience. It did drive some great things in my life, it just took its sweet time. I wish the same for you.

We're here if you need us!

[desertdogg]

Originally Posted by ls1nova71

Sorry to hear about your parents, that's rough. But good to see you back on the project.

Thanks ls1 ! It was pretty rough but I finally realized Im just wasting valuable time, and need to get this truck finished so I can start enjoying it with my family. Really glad to see you still on here ! you were a big help when I started this thread.

[desertdogg]

Originally Posted by skyphix

Welcome back - I've been in similar shoes to the ones you've been wearing and its not an enjoyable experience. It did drive some great things in my life, it just took its sweet time. I wish the same for you.

We're here if you need us!

Thanks skyphix !, Your right ! no fun at all, and yes sure took lots of time to get my butt back in gear, but the smoke has finally cleared and Im ready to finally get this done. Thanks for your response and future help on this Im going to need all the help I can get

[desertdogg]

Well, for the past week or so I have been clearing my garage, removing junk that piled on my truck and truck bed, it turned into a storage shelf so to speak for the past five years, Also took inventory of the parts I have and cleaned underneath, above and inside. I removed it off the jack stands and replaced the tires and wheels with some stock factory steel wheels I found on CL with some hub caps for now, the tires that were on it had gone flat and were pretty well dry rotted. All I have to do now is get my tools in order then try to figure out my next plan of attack on the truck. Got the day off today from work so I guess I better get started...back on here later !

[desertdogg]

Ok got my garage somewhat orderly and tools all in one place again but need to spend one more day just to get everything in order. I'm a bit ocd about having my surroundings where I work to be clean and know where everything is at, otherwise I just cant function lol !. Check back in tomorrow

[desertdogg]

Ok so my garage is at an acceptable working environment now and I spent some time mulling around the truck, mostly underneath, I remember back then I had run into this problem below regarding this previous transmission cross member brace see below

Does this look like a factory crossmember ? or is this an add on someone istalled ? I did buy a transmission crossmember for this combo truck and tranny do I need to cut this thing off ?



what do you guys think ? what would you do ?

[ls1nova71]

Definitely not factory. I cant see how its bolted in, but you should be able to slide it back and drill some new holes to make it work. As for the mount, if you get one for a 72 truck it will bolt on with two bolts that should line up with the holes in the crossmember. Or I guess you could just drill a hole in the center for the stud, but the bolts are easier to work with in my opinion.

[mongocanfly]

And if you do decide to use a tubing crossmember the mount tab needs to be on top of it...you can see where the tube is hitting the rubber in your pic...

[desertdogg]

Originally Posted by ls1nova71

Definitely not factory. I cant see how its bolted in, but you should be able to slide it back and drill some new holes to make it work. As for the mount, if you get one for a 72 truck it will bolt on with two bolts that should line up with the holes in the crossmember. Or I guess you could just drill a hole in the center for the stud, but the bolts are easier to work with in my opinion.

I have a feeling its welded to the frame but Im going to have to look at it tomorrow. Your probably right, I was thinking of making it work with that cross member but that's something I have to decide tomorrow as well. Thanks ls1 !

[desertdogg]

Originally Posted by mongocanfly

And if you do decide to use a tubing crossmember the mount tab needs to be on top of it...you can see where the tube is hitting the rubber in your pic...

Thanks for responding Mongocanfly ! Im not even sure which one I bought its still in the box I bought years ago. Im not sure what you mean about on top ? yes the mount is sitting on top of that member tab but Im assuming if it was closer the mounting pin would go thru the hole and bolted in place ? sorry If I sound lame just trying to understand

[mongocanfly]

Like this...mount tab on top of tube instead of on bottom side of tube...
if yours is welded in now, it won't work as is anyway..
But like Eric said...be better off with a factory one

[desertdogg]

Originally Posted by mongocanfly

Like this...mount tab on top of tube instead of on bottom side of tube...
if yours is welded in now, it won't work as is anyway..
But like Eric said...be better off with a factory one

Ok gotcha ! I see how someone can easily make that mistake. Thanks for clearing that up !. I just got home from work so Im going to be heading out to the garage for some more games after dinner

[bigmoe]

That home made crossmember may be throwing your pinion angle off if the trans height is wrong.

[desertdogg]

Originally Posted by bigmoe

That home made crossmember may be throwing your pinion angle off if the trans height is wrong.

Yeah that cross member is definitely welded in place which is a bummer. I thought about the height and angle, so I decided im going to have it towed to beeline alignment in the next couple of weeks and have them remove it and install the new member I bought. I thought about cutting off that tab and weld a new one that's a bit longer to make it fit but I decided to do it right, and just have that member replaced since I have one anyways.

I have been spending time on the wiring. the rear lighting harness needs to be replaced and I will be ordering a new one from LMC soon.

[dman1982]

Welcome back man!

[LH Lead-Foot]

Just a thought, but if you have a floor jack and a block of wood, jack it up, remove the crossmember and flip it over. It just needs a hole drilled in it.

If with is welded in and you don't have the equipment, it will take a lot work at a shop depending on flat rate for labor. This one is not in the book...it's tech time multiplied by customer pay.

Many post and experienced folks have discussed drive-line angles. A magnetic HF angle gauge with the transmissions crossmember out, use the floor jack to find the correct angle at the front, then measure across the frame to find out where it needs to live...with future exhaust requirements.

The rear axle want to climb upward when accelerating, but a minimum of 1/2 of 1 degree is the least anyone should place u-joints under load. These trailing arms on these trucks hold the rear axel well as compared to leaf spring suspensions.
This was discussed in GM's "Vibration analysis class". There several good vid's on youtube. Use the flat on each u-joint to find angles, then the math. Have u-joint movement rotates the u-joint needle bearings back & forth to keep them from being in one position all of the time. This helps reduce u-joint failure.

Maybe it's already been discussed during other post in the thread, but important.

[desertdogg]

Originally Posted by dman1982

Welcome back man!

Thanks man ! its great to be back !

[desertdogg]

Originally Posted by LH Lead-Foot

Just a thought, but if you have a floor jack and a block of wood, jack it up, remove the crossmember and flip it over. It just needs a hole drilled in it.

If with is welded in and you don't have the equipment, it will take a lot work at a shop depending on flat rate for labor. This one is not in the book...it's tech time multiplied by customer pay.

Many post and experienced folks have discussed drive-line angles. A magnetic HF angle gauge with the transmissions crossmember out, use the floor jack to find the correct angle at the front, then measure across the frame to find out where it needs to live...with future exhaust requirements.

The rear axle want to climb upward when accelerating, but a minimum of 1/2 of 1 degree is the least anyone should place u-joints under load. These trailing arms on these trucks hold the rear axel well as compared to leaf spring suspensions.
This was discussed in GM's "Vibration analysis class". There several good vid's on youtube. Use the flat on each u-joint to find angles, then the math. Have u-joint movement rotates the u-joint needle bearings back & forth to keep them from being in one position all of the time. This helps reduce u-joint failure.

Maybe it's already been discussed during other post in the thread, but important.

Thanks for the reply and help on this Lead-Foot. I have been contemplating this as I keep looking at it every time I'm underneath there. I did pull the drive shaft out and put the Yoke in the tranny and all the way back to the Dif. it looks like its a perfect fit ! which I'm pretty happy about. I was thinking about cutting off that tab where the tranny mount is resting and weld a new longer tab on top of that crossmember as everyone seems to think it needs to be on top, I think this would be the easiest option. I just don't understand this pinion angle thing. I'm going to have to research the threads on here like you say and see if I can get a clue. Thanks again !

[LH Lead-Foot]

On vehicles with leaf springs, the diff will move up in front as you accelerate. With a 67 -72 C10, C20 using lower control arms, the differential is locked to the movement of the control arms. So, hit the gas, the diff climbs the ring gear, that motion is transferred to the housing. It is captured, so the differential rises toward the floor, as the back end bed drops.
The nose of the differential rises up to be more inline with the tail shaft of transmission. This position is normal under hard drive, but drops at cruise.

So, place the rear u-joint with a flat on top. Place some weight in the back bed like 200 lbs. This will drop the bed, but raise they differential since it's captured. Take a measurement on the top of the rear u-joint. make note. Compare that measurement to the unloaded empty bed on the u-joint at the same top position.

Do the same at the transmission front u-joint top when flat while empty, take note. Even when the bed is full or not, the front u-joint does not move anything noticeable, take measurement. The two angle should be at least 1/2 of 1 degree to 2 degrees of difference. You should be in range of good u-joint movement and no acceleration / deceleration within the u-joint range.

Should be good to go. (Note: If stock height info, good...lowered or raised, angles may have to be modified as needed) Good build.

Late reply, I am sorry. Bad doctor news today for 60 year old guy...all bad! I'll let it go. You have a "Best if Used By Date" it's just to read in a mirror! We don't last forever.

[desertdogg]

Originally Posted by LH Lead-Foot

On vehicles with leaf springs, the diff will move up in front as you accelerate. With a 67 -72 C10, C20 using lower control arms, the differential is locked to the movement of the control arms. So, hit the gas, the diff climbs the ring gear, that motion is transferred to the housing. It is captured, so the differential rises toward the floor, as the back end bed drops.
The nose of the differential rises up to be more inline with the tail shaft of transmission. This position is normal under hard drive, but drops at cruise.

So, place the rear u-joint with a flat on top. Place some weight in the back bed like 200 lbs. This will drop the bed, but raise they differential since it's captured. Take a measurement on the top of the rear u-joint. make note. Compare that measurement to the unloaded empty bed on the u-joint at the same top position.

Do the same at the transmission front u-joint top when flat while empty, take note. Even when the bed is full or not, the front u-joint does not move anything noticeable, take measurement. The two angle should be at least 1/2 of 1 degree to 2 degrees of difference. You should be in range of good u-joint movement and no acceleration / deceleration within the u-joint range.

Should be good to go. (Note: If stock height info, good...lowered or raised, angles may have to be modified as needed) Good build.

Late reply, I am sorry. Bad doctor news today for 60 year old guy...all bad! I'll let it go. You have a "Best if Used By Date" it's just to read in a mirror! We don't last forever.

Lead-Foot thanks for this good information I was just reading some of the pinion angle threads and I didn't realize it had to be at ride height, of course my truck is sitting on jack stands so Im thinking I need to raise my truck and let it sit on some wooden boards on all four tires so I can get underneath it, my truck is lowered so this is the only way I can think of working under neath it. I also need to get an inclinometer gauge.


Sorry to hear about your doctors appointment, I hope its nothing too serious and you can get better. Your right we don't last forever and that's one of the reasons I want to get this truck done, while I still have the ability to do so. 60 is still young Im not too far behind you and starting to move real slow again thanks for your help !

[desertdogg]

Originally Posted by LH Lead-Foot

On vehicles with leaf springs, the diff will move up in front as you accelerate. With a 67 -72 C10, C20 using lower control arms, the differential is locked to the movement of the control arms. So, hit the gas, the diff climbs the ring gear, that motion is transferred to the housing. It is captured, so the differential rises toward the floor, as the back end bed drops.
The nose of the differential rises up to be more inline with the tail shaft of transmission. This position is normal under hard drive, but drops at cruise.

So, place the rear u-joint with a flat on top. Place some weight in the back bed like 200 lbs. This will drop the bed, but raise they differential since it's captured. Take a measurement on the top of the rear u-joint. make note. Compare that measurement to the unloaded empty bed on the u-joint at the same top position.

Do the same at the transmission front u-joint top when flat while empty, take note. Even when the bed is full or not, the front u-joint does not move anything noticeable, take measurement. The two angle should be at least 1/2 of 1 degree to 2 degrees of difference. You should be in range of good u-joint movement and no acceleration / deceleration within the u-joint range.

Should be good to go. (Note: If stock height info, good...lowered or raised, angles may have to be modified as needed) Good build.

Late reply, I am sorry. Bad doctor news today for 60 year old guy...all bad! I'll let it go. You have a "Best if Used By Date" it's just to read in a mirror! We don't last forever.

Lead-Foot thanks for this good information I was just reading some of the pinion angle threads and I didn't realize it had to be at ride height, of course my truck is sitting on jack stands so Im thinking I need to raise my truck and let it sit on some wooden boards on all four tires so I can get underneath it, my truck is lowered so this is the only way I can think of working under neath it. I also need to get an inclinometer gauge.


Sorry to hear about your doctors appointment, I hope its nothing too serious and you can get better. Your right we don't last forever and that's one of the reasons I want to get this truck done, while I still have the ability to do so. 60 is still young Im not too far behind you and starting to move real slow again thanks for your help !