Saab 900 trans check up

[DeLorean]

So today I finished up with the "check up" on the 93 900-t trans going into the 88 SPG after the recent primary drive case failure on the 89-90 box it had. This is about the 7th trans this car has... "consumed" Took it apart, everything was good except for a few minor things. The main gear cluster needle bearings were worn, as were as the reverse gear & Idler gear (which was badly beaten by the previous driver of the car). Also the 1-2 syncro hub was not in good condition either so I replaced that. The car it came out of only had an indicated 53K on it, though I suspect it was higher due to the condition of the reverse gear and 1-2 syncro hub. Everything else looks perfectly fine, no damage to any of the gears, pinion bearing is still well in spec. popped it all back together and rantested it with the drill, looking good.

We'll see how long this one lasts before a gear cluster or case failure... I am getting rather tired of doing this over and over again Anyone feel like making me a better gearbox case? :lol: The really crappy part is I have never had a typical high mileage failure, it's always either a blown gearcluster or a broken case. last time it was a broken case, at least the main case and the rest of the trans I'm pretty sure is still 100% serviceable, just needs a new front case!

[Crazyswede]

you could turn down the boost a little or change the way you drive it. I managed to get at least 30,000 or 40,000 miles out of a rebuilt 82 900 turbo gearbox...that already had 100,000 miles on it. The car had a 2.3 head and many other goodies and in the end the engine and transmission along with the car were used by airsweden for ice racing. It was then that the transmission failed but not after several ice races....if I remember correctly it failed when he was running these tires (more grip than a street tire on pavement):

[DeLorean]

well, it dos not even have THAT much boost, the TD04HL 16T makes pretty impressive power even at relatively low boost. I do drive is fairly easily too under most conditions, though I do go to WOT in 4th and 5th pretty often.

The car does make enough power to run 36# injectors up to 95% duty cycle, so it's making good power here. I think some case stiffening measures, along with an extra bearing in the front cover for the upper sprocket would help matters greatly... anyone know where I could get a reinforced front section with an extra bearing??

[Luke]

damn 7 trannies! My first 86 SPG I got from the original owner at 170k I drove past 300k on the original gearbox (it had started to whine a little though). I've only ever killed one really badly in 12 years of driving c900's everyday and that was when I let my girlfriend drive the car that had a 3 puck sintered iron solid hub clutch, it developed a horrible shudder if you didn't slip it just right.

[Geoff]

Yeah, I've really only blown one manual box in the past 12 years too. Of course I sold an '85 900S to a neighbor who quickly busted the box in it after I had driven it for a while...

You could get a steel rear diff cover from Luke. Jorgen can make the 4 chain primary drive with the extra bearing in the primary case but he didn't seem to keen on it when I asked him about it. He also has some chains that are stronger than stock.

[DeLorean]

the 88's trans history--

#1 (suspected original) developed pinion noise and poor shifter action shortly after, replaced before total failure
#2 (newringold "all you can carry day special") $10. 91-93 trans. did nothing but install it, worked fine for about 10K, then blew 3rd gear without warning
#3 CRS 91-93 rebuild trans, recent rebuild found in junk yard. worked fine for about 15K miles, then blew 4th gear no warning
#4 CRS reduild (same trans) rebuilt with new gearclusters, drain plug fell out on the highway and finished it off.... yeah, I thought that was tight!
#5 Eriksson Industries 91-93 trans I bought from them! 1 year warranty. Blown 4rh gearcluster in less than 10K miles
#5 Eriksson Industries warranty replacement. Blown pinion shaft in sub 3K miles, I was able to drive it for a bit after that with it clicking, just JB welded the case.
#6 junk yard 89 trans. did nothing to it, just installed it. this has been the best trans by far. lasted about 25K, and the case broke by the upper sprocket
#7 is the one going in now!

[airsweden]

Seth's old 300k mi 5spd went south about 2.5 hrs into a 3 hr icerace in Moosehead, ME. The 1.5 mi course had developed giant piles of ice chips everywhere that would let the wheels spin, then you'd snag traction on the clear ice. I think the constant on and off loading and heat buildup were just too much for the old dog.

Since I had driven it up, I thought I would take what I could and then just leave the car there for the vultures to pick over. But, the AMEC crew shuffled some cars around on the trailers and we managed to get it home. There were 3 VW Golfs on a 2 car trailer, that freed up space for me on a dolly.

That was the first time I toasted a gearbox. Since then I've run a 4spd with mixed results. One mashed cluster gear at Mike Kamm's dirt/pavement wheel to wheel rally-x and one just driving along at about 45 mph on my way to work (strange one).

I have a heavy duty 4spd (big gears and no syncro) that needs to be reassembled. I was wondering about treating the gears first. Anybody know much about cryo or shot peening? Is this even a good Idea? I just thought since its apart maybe I should look into preventative measures.

Josh

[Crazyswede]

I do not know if its worth having the gears cryo'd or shot peened. The gears in that box are bigger then stock. The reason that the stock gears usualy break is that the case flexes and the gear shafts pull apart. This causes the stress on the gear surface to go up dramatically and the gear tooth chips or breaks..leading to a rapid failure. You might look into REM tumble though....good for making the gears nice and smooth and helps with lubrication...gets rid of microvoids etc. We have a REM tumble machine here at work but they would not be thrilled if I threw my own parts in.

[stig-swoosh]

I've been curious about REM finishing.
Since this place is pretty close to me it'd be
easy to get it done...
http://www.evansperformance.com/home2.html

...and it's cheaper than I thought it'd be according
to this joint:
http://www.mrracingequipment.com/M&R%20Racing%20Equipment%20-%20rem.htm

So you think it's worth the bread to get this process done?

[Crazyswede]

Well we make blades for GE aircraft engines and the REM tumble machines are used to improve the surface finish. The system uses a tumble media combined with an etching acid. The process removes the peaks and surface irregularities. The benefit that you would see in a racing box would be decreased friction between gears and theoretically better contact...probably better lubrication. I do not know if its worth the fee.....it might be one of those things thats no so beneficial to a Saab gearbox...but very helpful to a formula 1 car thats running 200 mph.

[Jordan]

I'd think less friction/heat and better lubrication would help just about any gearbox. You would need to do some quantitative analysis though to see if it's a .01 degree or 10 degree difference to know what the value is.

[Crazyswede]

yes less heat and less friction would be beneficial....but as you say is it a .1% improvement or a 5% or 20% etc. The money spent on REM tumble might have a greater impact and benefit if spent on case strengthening, peening, cryogenic freezing, or upgraded parts etc. If the REM tumble is $100 then it might be worth a try. if its $500 I would probably do other stuff first.

[Jordan]

I think changing the trans fluid often helps a lot. It always amazes me that after one or two rallies how blackish red and degraded the fluid in Luke's car gets. I'm going to make it a point to change the fluid out in my car after every couple major events. Especially with a clutch dif in there. A trans fluid cooler would also be a cheaper alternative.

[DeLorean]

I think changing the trans fluid often helps a lot.

I used to think that, I would change it just about every other oil change, did not seem to help... the last trans (one of the longest lived) I never changed the fluid once, and it even had some of the fluid left over that it came with from, the junk yard! :lol:

[saab90089]

I think changing the trans fluid often helps a lot.

I would have to agree with this. All of our C900 transmissions tend to last 220K + miles. We change our gearbox oil around 30-40K miles and are sure to use 75w-90 GL5 accept we replace 1 Pt. with Slick50. We can't be sure the slick50 does anything but it's cheap and has yet to hinder anything so we are going to stick with it.

My dad and I also noticed while looking through the 1992 900 owners manual they say that 10w-30 (just 30 weight?) is what should be used and GL5 as an alturnative. My dad and I wondered if this in addition to the lack of drain plug was the major cause for later-year C900 transmissions dieing earlier.

Ian