CV extension

[tarsh]

Hey fellas, i recently purchased some 89 springs. I'm Waiting to install them because both my inner cv boots are torn and need repacking. Want some opinions on extending my cv shafts, obviously i have a brain on customizing things or i woulnt have asked. Just looking for opinions here. Say i was ro extend them one inch. To brevent bindings. do you guys think it would help?

[HARDTRAILZ]

No.

[tarsh]

Really? Just no... By extending by say an inch wouldn't help by pushing the cv joints into the tripot allowing more "flex" in the front?before cv binding occurs? Or seperation... Or whatever you wana call it

[v7guy]

Think about suspensions, when double a arms cycle they travel in an arc. This requires that there's plunge available. The axle has to be able to travel in and out a bit. It's going to be at the outside edge of the tripot on full compression and full extension of the suspension. In the middle of the travel it's going to be pushed towards the inside of the tripot.
If you lengthen the CV axle it's going to bottom out in the bore of the tripot and bind up and or break when the suspension cycles.

I have seen some toyota guys notch the tripot housing to get more travel. But in gaining more travel you give up turning at the outer CV since the CV only has so much angular ability.

[tarsh]

I know that, im just curiouse of how much room there actually is at compression. There gitta be a small void that can/could be filled. Maybe ill just have to do some investigateing when i rebuild it.

[ErikSS]

I considered doing this. I brought my Trailblazer to a drive shaft shop. They looked at it and said there was no reason at all to lengthen the CV shafts.

[Trail X]

Lengthening the CVs would only cause more binding. Your only potential to get more cv travel is to shorten the cv shaft itself, bringing the tripod joint closer to the mouth of the tripod housing. However, you risk pulling the tripod out of the housing during suspension cycling if its too close to the mouth. Contrary to what Jason said, a properly designed suspension really doesn't require much of the tripod's plunge while it cycles up and down. The overall length of the plunge is mainly driven by the suspension alignment adjustments.

[tarsh]

Ok, so let's say I was to place a retaining nut on the inside of the hub to compress the cv together and then put another nut on the outside of the hub as normal, obviously marking sure the splines are still in.

[Trail X]

If you're talking about spacing out the CV from the wheel hub on the inside to effectively plunge the tripod joint deeper into its housing, that is a very bad idea. Read the above comments. The only possible thing that I could see to be very slightly beneficial is to space out your hub with a plate, but I don't like the idea of changing the way the hub interfaces with the knuckle, so I wouldn't do that either.

[rScherzer]

Just my 2 cents here, Our front half shaft only can take so much of a deg/angle before it will bind. I have worked on both lift kits for the IFS (mainly GM) and on IRS (930/934) rear suspension. On the IFS the way they are accommodating the lift is by spacing out the half shaft on the diff side and using a offset knuckle. Unfortunately for us GM though using a spline type tripot was a good idea. On the IRS suspension there are a few different designs I have come across that seem good, and some not so good. With what I have gathered, you would need to remove you shock/strut and reinstall the front axle. Then position the suspension so that the axle is perfectly level. This would show you the minimum length required by your setup. Then you would move it to the full up and down travel and take second measurements. Like its been stated before, our half shafts/cv shaft can only take so much before they bind. So the only way I could see something working is actually moving the diff assembly down and then getting a custom make front knuckle that would also accommodate the drop. (this would also require the lower control arms to be repositioned lower. I have been looking at all sorts of stuff from the H3 front suspension to a full SAS conversion.

[v7guy]

I was trying to be very simplistic in my initial description. Given the initial question, I didn't really see that a more thorough explanation was needed. So to be more detailed...

There's a line from the upper ball joint to the lower ball joint. The outer CV has to sit on this line. Otherwise you get plunge. There's also another line that runs from the upper a arm bushings to the lower a arm bushings. The inner tripot needs to sit on this line, otherwise you get plunge. Moving either one of the CV axle joints out of the plane they're on is generally going to be detrimental.

There's very little actual plunge in stock applications as James mentioned. Long travel stuff sees it at the extremes of travel, but with plunge you get a tremendous amount of heat, over time, break down of grease, and destruction of the joint.

Robert and James brings up a decent option and a way to go about it, if you removed the tripot boot and put everything together minus the shock you could cycle the suspension and see how far out you could position the bearings in the tripot. As they mentioned shortening it might actually gain you something. It would be rather minimal though.

Robert, I think you'll find that dropping the front diff would be very undesirable unless you remove the front subframe cause you would need to drop the CV below the subframe, that's more than 6". Might be able to squeeze a Colorado front diff in the stock subframe and gain a locker. But you're talking a lot of fab.

[rScherzer]

I totaly spaced the front sub frame. I got cought up in the angle of the dangle and stuff. I did a bit of google searching and came across a few articles that talk about max angles of the cv joints to be around 47 deg to 51 deg before binding. With than and the sub frame in mind and a fresh cup of cofee. I think that fabing a inner flange joint (like the 1/2 ton front diffs have) then installing a spacer to move the axle out along with a custom front knuckle would be one way. Personly I think a SAS would be cheaper, and easier to do. On the original topic I had a idea that if you cleaned all the grease out of the tripot and put a bit of clay in the bottom, cycled the suspension to see how much more room you have. Just a idea.

[v7guy]

Using some clay or play-doh would be a good way to determine the room you had to work with. I used play-doh to iron out my oil pump pick up height in the rear sump pan. It works well.

As far as ease of the conversion, an SAS is the way to go. I'm definitely pushing myself with this IFS work. Admittedly I don't have a ton of fab experience. So your results may vary. lol

When discussions on building an IFS come up I try to keep it basic and simple but there's no way to cover it and be accurate because everything affects everything else. It's a fairly involved subject and you have to have a grasp of how everything interacts or you end up making the system work worse.

While we spend a lot of time bemoaning GM for their choices it really is (overall) a pretty ingenious design for what it was originally intended for. It just so happens it doesn't mesh well for what we're doing when you get to the extremes. As more time passes I'm more and more convinced with the bigger rear axle it's a pretty solid and reliable platform for 33s.