I figured they would be the same length. Matched the U-joints up in the back, and the Spohn is ~1" shorter at the front. Shaft length looks about the same, but the slip-yoke is what's shorter. I would have ~2" of engagement in the trans vs. ~3" with the stocker. What is the minimum?

Is this normal/expected/on purpose? I have the rear diff is on jack stands, so it's not hanging.

I can see if I used adjustable LCA's to move the axle forward, I would get more engagement (as long as I didn't twist the output shaft before then). I know the pinion of the rear end will twist 'up' on a hard launch. Not sure if it's enough to warrant a 1" shorter driveshaft.

I will ask Spohn tomorrow but wanted any input from you guys.
Thanks.

 

I found this:
http://support.spohn.net/questions/2...e+transmission.

I see what they're saying about the slip yoke, but mine is definitely shorter and not as far in the trans. I guess as long as "enough" is in, whatever that may be...

 

New driveshaft is the same length from u-joint center to u-joint center. The difference is in the yoke, new driveshaft is 1 1/4" shorter, all yoke.

Spohn driveshaft has a 3 3/4" yoke, and 1 3/4" is exposed, leaving 2" engaged in the tailshaft. Stocker had 3 1/2" engaged in the tailshaft.

I understand the need for ~1" of travel, which I had (as did the stocker). On the phone, Spohn explained to me that the 1350 u-joint is shorter than the stocker (even though their FAQ says it's longer? ). I chatted with them online too, and they said it will be fine. I guess it will. I just don't know if I like having that much less engaged.


-------------------------------------------------------

Hello Dave, this is Spohn Live Support, how may I help you?

Dave
I am reading this link here: http://support.spohn.net/questions/2...e+transmission.

Spohn Live Support
ok

Dave
Where it states a 1350 slip yoke is 1" longer than the stock LT1 driveshaft
I got my driveshaft yesterday, but the overall length is 1 1/4" shorter than factory
It says the yoke is 1" longer, but in actuality it's 1" shorter, and I have a whole lot less inside my transmission now.
(on my output shaft)

Spohn Live Support
What driveshaft did you buy?
What is the name you placed your order under?

Dave
93-97 F-body Stock Trans
LMC115
David xxxxxxxxx

Spohn Live Support
Looking at your pic it looks correct. It should measure 41" c-c u-joint
our driveshaft are about 1/4" shorter than factory due to higher HP cars giving a little more travel

Dave
Yeah, the 'tube' itself looks like the correct length.
Overall it is 1 1/4" shorter

Spohn Live Support
You do have the correct set up for your car.

Dave
Total yoke length is 3 3/4". There is 1 3/4" 'hanging out' of the tailshaft
Leaving 2" engaged on the tailshaft. Factory has approx 3" engaged. Will this be an issue, or is there a minimum required to be engaged?

Spohn Live Support
That is because the yoke is not the same as factory yoke. It still has the same engaged on the inside. No this won't be an issue. Honestly we've sold 100
'100's of these specific drive shafts

Dave
Yeah I believe you that you've sold many of these. I'm just not understanding how the same amount is engaged inside the tailshaft, when it's clearly 1 1/4" shorter
I understand the illusion of there being 'extra' on the outside of the tailshaft.

Spohn Live Support
If your unhappy with your purchase you can go ahead and ship it back. Would you like an RMA #?

Dave
I'm not unhappy, I haven't driven on it yet. I just didn't want to hurt anything with there being a lot less engaged in the tailshaft.
Which you are saying is not the case, but mathematically, I don't see how is possible.

Spohn Live Support
No nothing will be hurt by this set up. Looking at it I understand what your worried about honestly there is enough engaged in your trani you will just have slightly more travel now.

Dave
OK. I have seen some trans output shafts have the splines twist, and I'm not sure if that was because there wasn't enough driveshaft in there, so it was easier to twist or what. I didn't want that happening with mine.
If you guys say it's OK, then I'll go with that. Just trying to cover my bases, as it looked funny to a few of us.

Spohn Live Support
No its completely fine to question it. It does seem very "out there" but we use the exact same thing on our own cars.

 

With the rear u-joint in the pinion yoke, how much clearance is there between the trans output shaft and the bottom of the slider? To measure, starting with the u-joint seated in the pinion yoke, push the DS forward into the trans until it bottoms out. That distance is the clearance. A stocker will typically only have 1/2" of clearance. High power DS's are usually set for up to 1" of clearance.

 

Dave, if you have an aftermarket rear end, you may need a shorter driveshaft anyway. When I bought my driveshaft from Spohn, I did my Moser 12 bolt rear end at the same time and the drivehhaft was too long. Mine was the same length as stock and there wasn't enough play. I ended up moving the rear end back a little bit since the suspension was all adjustable.

 

Fred, is this what you're talking about here? There is a 1 3/4" hanging out of the tailshaft. I didn't push it forward to see where it would bottom out at. Unless something inside the tailshaft prevents it, I think it would completely bottom out in the transmission, giving me 1 3/4" of travel. 2" would be engaged in the transmission.

Spohn is saying this is fine...but I don't know. If I got a 12-bolt or 9" or taller tires and moved the axle forward maybe it would be better. Again, I don't really know...

 

You have to see how far it will push in.

 

I need a lift. I am tired of jacking this car up. Have to see what I can find that will fit under an 8'6" ceiling. Well, that's another thread. I'll push it in and see where it lands.

 

I just had the same issue when swapping driveshafts. Your stock DS had the yoke with damper (the big circle). There are two types of aftermarket yokes (that I found), short and long. You need the long version since yours originally had the damper.

I gave Denny a call from Denny's driveshafts and he walked me through all this. I ended up getting the forged 1350/s44 combination long yoke. I could NOT find a replacement that works with the stock s44 ujoints that came in the long version, so I had to go with a conversion. Not sure what ujoints you're using but most yokes comes in the Spicer 1310/1330/1350 styles, so you'll need a conversion joint as well.

 

OK I reread your comments and went through my notes on measurements that I took. You definitely do not want to use that DS, you're losing a full inch of engagement depth. You need a yoke with approx total length of 7 1/2" long, with a barrel length of about 4 5/8 inches. It looks like the DS you have is already 1350 series so it should be easy to find a yoke and not have to worry about a conversion joint. You'll want to make sure it's NON-VENTED, or you'll have to weld the vent hole shut. I would up purchasing part # 7527580 from Denny, but looks like he is out of stock. Whatever you do, but sure you get measurements of the critical yoke dimensions rather than relying on an "interchange" chart.

 

I will take a closer look at everything when I get home tonight, to include what Fred said about measuring the difference between bottomed out, and the rear u-joint seated. I have a feeling that I will be able to bottom it out, making 1 3/4" of travel.

I don't know why Spohn is so adamant about this being correct. I understand what they are saying about it visually looking like more is sticking out of the transmission, because the 'donut' is gone, but there is obviously less engaged in the transmission as well.

Why did you need a conversion joint? Do they not make a 1350 long-yoke? Or do I really even need a longer yoke? Maybe just a longer driveshaft 'tube'?

Mine should be 1350 on the front, and a conversion on the back from 1350 to stock.

I didn't think about the venting either, I will look at that too.

Here is the yoke you mentioned:
http://www.dennysdriveshaft.com/p112...0_series_.html

I don't know if I should say to hell with Spohn and send this driveshaft back to them, and have them give me a longer one with this slip yoke; or order that Slip-Yoke and get it installed/install it here and be done with it, or think that Spohn is jerking me around, ****can them altogether, and get a unit from Denny's.

 

Is this the same one you were looking for?
http://www.riversidegear.com/drivesh...27-spline.html

 

I needed a conversion joint because I am using a stock GM alum DS which is fitted for s44 joints. I could not find a yoke in s44 that was the right length, only the 1330 or 1350 series so I needed to get a conversion joint and went with the s44-1350 combo. Your DS looks fine as it is identical in length to the stock, your only issue changing from the stock yoke w/ damper to a non-damped yoke which is the same situation I had. Keeping it 1350 throughout will be much stronger than my setup as well.

I'd keep the DS and return the yoke, unless they will only accept the whole unit as a return. For sure give Denny a call and he will be happy to chat your ear off and make sure you get the right part.

Edit: just reread and saw you are running the same conversion joint but in the rear instead of the yoke like I am. This setup isn't really any stronger than stock, only reason I did the swap was that it was time to replace the joints anyway and I wanted the lighter AL DS since I was doing it anyway. Not sure if this would be a factor in your build, but just FYI the conversion joint is the weakest link in the driveshaft assembly until you get a 1350 rear end.

 

Working out in the garage now. I can say with 100% certainty that the yoke pushes completely in until it bottoms out on the rubber seal, giving me ~1 3/4" of travel. This is 3/4"-1" more than is recommended, and I'd damn sure rather have that be engaged on the splines of the output shaft.

It's kind of stupid that you pay $375 for this driveshaft, and have to go elsewhere for the correct yoke. I will probably destroy the u-joints swapping yokes; well, they're new, maybe I can get away without destroying them. Either way; I'm frustrated.

Yeah I have the conversion joint in the rear, because like you said I still have the factory 10-bolt in there. Spohn told me when I get a 9" or a 12-bolt, I can just swap that out for a true 1350 u-joint. Unless I go with a S60, then I think the driveshaft is too long.

I mainly got this driveshaft because I had horrible vibrations at 80+ MPH and wanted the to go away; and I had my buddy's stock driveshaft let go on me doing ~100 MPH and scared the **** out of me. I hear that same vibration with my stocker and I get an uneasy feeling.


I noticed on Spohn's site that you can get an upgraded "Strange Chromoly" slip yoke for an additional $115. I don't know if that is the same size or if it's the longer one. Should be standard.

 

OK, just because pictures make everything better.

Fully seated. That silver line is from the silver sharpie I used.



1 1/2" of travel:



5 1/2" center-to-end:



7" center-to-end:



3 1/4" of engagement:



2 1/8" of engagement: