Some c900 diagnostic help

[li Arc]

I've finally gotten around to swapping the inner drivers with my known good transmission, but that didn't fix the problem. In fact, the problem feels exactly the same as before, with vibrations only when turning right, whether accelerating or decelerating, and increases with the steering angle only. Anywhere from straight to the left are vibration-free.

The ex-Saab mechanic I spoke to bet on it being a driveline problem, somewhere along the way. Which means since it's not inner drivers and it's not the LHS wheel bearing, it can either be the axles (or more likely, one of the inner or outer CVs), or the RHS wheel bearing. What doesn't make sense is the inner drivers were the only "foreign" part in the system, which is what was the most likely culprit since the vibrations didn't exist before I rebuilt everything. So I'm wondering if some change could have caused this problem instead, ie. chillcast case requires different length axles or something? Hopefully I can go to the yard this weekend and pull axles from the '85 there, which is the same as mine, and test replacing the entire axle assembly on each side. Hopefully the inner CVs are the same as mine.

li Arc

[Jordan]

the drivers did change sizes a few times I believe between 4 and 5 speed revisions. That's what people have told me, but I have never had a bunch and measured them myself.

[DeLorean]

What size tripod bearings are you using? Are they still in good condition too? It would be impossible to use 86+tripod bearings in the old style inner drivers, but would be entirely possibly do to the other way around. What year are your axles from (85 or earlier?) cause if they are, they are likely the smaller type. What inner drivers are you running (85 and below or 86-93)

Pretty frequently on higher HP cars, or just higher mileage cars the needle bearings that hold the tripood bearings together will fail on one of the 3, and you will get a pretty strange vibration from this.

Also check other obvious things. Are your engine mounts broken? are the upper A-arm bushings bad?

[DrewP]

I'm with Delo, it's probably something off the wall at this point, though the other wheel bearing wouldn't be a bad idea since you'll have the whole thing apart again anyway.

Is it possible one of the tripod rollers came off and it didn't get all the needle bearings put back in? I've tried to install axles before and got the tripod roller hooked on the edge of the cup and it'll pop the roller off. It takes a long time to dig through all the grease to find all the needles if they come out.

ALSO: Check out this post. I have seen the outer CV joints assembled incorrectly and it will make them bind up weird.

viewtopic.php?f=18&t=1718&p=22691&hilit=#p22691

If you hold the halfshaft and swivel the outer joint around in a circle it should move freely and smoothly through any position. If you feel it stick or bind or click or anything like that it could be your problem.

If you have never taken a CV apart before be ready to have some fun - practice on an old one first. Getting them apart and back together takes some patience.

[SwedeSport]

There were 2 different shaft lengths in the mid 80s. I believe it was 5 mm difference. They compensated for the different hubs used on vented/non vented brakes.

The Bentley manual was the source of this info, might be worth looking into.

Either way... it could be a year/model parts interchange thing.

[li Arc]

No doubt about it, my inner tripods are 37mm, the larger size (measured with a caliper), and I've got 37mm inner drivers to go with it. When I was still green and had a mechanic replace my whiney '85 transmission with an '86, it's possible it got changed, I don't know. At any rate, I've also got inner drivers that won't fit overtop the tripods, so it's fairly obvious. That and it's also fairly obvious when one doesn't fit into the other properly.

Interesting theory about the outer CV wear...as the local Pick & Pull has an '85 in the yard (surprising, given c900's rarity here), I'll be pulling the entire axles if they're still available, and transplanting the entire thing over to see what's what. Even if something in the axles are bad, it can't possibly generate the same vibration I'm seeing unless it's not the axles, at least that's my theory.

Axle lengths were also something I was worried about as well, as I'm not clear on when they changed and how many different types there are. This chillcast case is I believe from a '78 or '79 99 (maybe turbo), though I assume there were no axle length changes between the 99 and the 900, not sure.

Guess we'll see more over the weekend.

li Arc

[Jordan]

There were definitely axle length changes between 99 and 900

[li Arc]

Really? So for those who have managed to get a chillcast case into their c900, have you needed to transplant the axles from the 99 as well?

I headed out to the yard over the weekend, only to find that the wheels are free spinning, and I don't have a portable impact driver, so those aren't coming off. There's one other source I might be able to get some old axles from in the city, but it's not guaranteed. If I needed to get new axles, I may have to grab them from eeuro, as no one carries them up here. I've heard mediocre things about the EMPI brand complete axles, what are your opinions? An inner tripod alone is $75 from eeuro, would I be able to transplant the components from the EMPI axles onto the stock axle (I have heard the axle shaft isn't as good as stock)? Should I get 99 axles instead? What about my 37mm drivers, should I get the inner tripods separately anyhow?

I'll try putting it up on jackstands and seeing if I can find what's what while it's running, and I may also pull the outer CVs and check them, but from visual inspections the inner driver and tripod aren't problems. I would still like a set of complete separate axles to eliminate all the variables though...

Update: from an old post elsewhere, RHS 62cm, LHS 56.6cm length axles

li Arc

[li Arc]

It also appears there are other options. A1 Cardone remanufactures old axles, which might actually be a better bet than EMPI. I'm just trying to figure:

1) Axle lengths (years, models)?
2) Year that the tripods went from small (34mm??) to large (37mm)

Maybe I'll give these a shot, they seem to be decently priced and have warranty on it.

Update: found some information on the tripods in a transmission training manual, apparently '85 turbos got the larger tripods, then this got phased in on non-turbos in '86+, so I believe my tripod bearings are original...if I order '85 turbo half shafts from Cardone, that should do it I think...unless axle lengths are different due to the chillcast case...

li Arc

[SwedeSport]

As per the Bentley 16v manual.

[MattWatson]

I headed out to the yard over the weekend, only to find that the wheels are free spinning, and I don't have a portable impact driver, so those aren't coming off.

I take it from that you are in Calgary then. I wondered. I tried to get the rear axle off that thing for my 99, but wasn't able to get the wheels off the back either. Then I ran outta time.

What is odd is they didn't take them off before they jacked it up, which they seem to do with all the cars there. so maybe they didn't have any luck either!

I'll let you know if I head back out, if I do, i'll take the front wheels off for you (assuming I can). I may have a friend with a rear axle, so I may not bother, just havn't phoned him to check.

[MattWatson]

As per the Bentley 16v manual.

What did they do to compensate for the additional distance? Just a change in the hub?

I was planning on swapping a fresh rebuilt 92 transmission with the larger inner drivers installed and full axle set out of a 90... but if I would need the hub, then that is a no go seeing as I am using a 86 turbo hub and upright with wilwoods.

[SwedeSport]

I believe it was due to the change to the vented rotors.

[MattWatson]

I believe it was due to the change to the vented rotors.

Humm well I will have to do some measuring this weekend then, because I may have to swap to those then anyway :) Seeing as the 86t were vented anyway, and there was a change in the hubs that year.

But, enough of thread jacking... Might as well just start my build thread realistically...

[li Arc]

I take it from that you are in Calgary then. I wondered.

I'll let you know if I head back out, if I do, i'll take the front wheels off for you (assuming I can). I may have a friend with a rear axle, so I may not bother, just havn't phoned him to check.

Wow, surprised to find someone on here who's local! Yes, I'm in Calgary, and they had only the one '85 there. I just updated my post though, with the fact that the '85 turbo is the first year to get the 37mm tripod bearings; the one at the yard is an 8V NA, so the tripods won't be the same. The rest of the axle might be handy, but if I'm looking at a remanned axle from Cardone, I'll just not worry about the ones at the yard. I'm pretty sure you'll need a cordless impact driver to get stuff off it now!

Since none of the transmission or drivetrain bits are past 87, I guess the 900's axle length changes don't affect me. I'm still worried that axle lengths have changed between the chillcast year (probably a '78 or '79 99T) and my '85, so I'm holding off the axle purchase until I get more information on this (and a reply from another enthusiast in town with regards to his collection of Saab parts).

li Arc