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Transmission Rebuild Experience Posted by eric in vermont [Email]  (#2058) [Profile/Gallery]
(more from eric in vermont) on Mon, 10 Mar 2008 14:43:35
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Dear VSaab enthusiasts,
Based on the previous posts on transmission rebuilding, I'll share a couple of my experiences with rebuilds that might offer some help to people contemplating it.
First, about me- a backyard mechanic with reasonable skills and tools. Not afraid of tearing into any problem. Been taking care of my cars since HS, back in the '70's. I'm an aerospace systems engineer by trade, so try to attack things based on my training.
My first Sonett came with a broken gearbox. Armed with Saab and Haynes manuals, I took off the top cover/rear cover and found bad bearings and loose shaft nuts. An experienced VSaab handyman helped me take it apart, change just the bad bearings, and put it all back together. We did not change the R&P adjustments and we reused the shims in the back cover, nor did we disassemble everything on the shafts or inspect the needle bearings. I did all this with normal mechanic's tools- no presses, jigs, bearing pullers. Just on the bench with hand tools. Car has been driven quite hard for 15 years and the trans is doing just fine- no noise, whine or problems. Assessment- I got lucky. It wasn't hard, but it sure helped to have a knowledgeable friend by my side. Plus, nothing was broken or worn out too bad, except the bearings.
My second Sonett came with...yes...a broken gearbox. I took it apart and found broken teeth on 4th gear as well as a badly chipped R&P. Junk. I had a spare Sonett gearbox and took that apart. It seemed to be in decent shape with nothing apparently bad. This second Sonett has a fancy Jack Lawrence motor- overbored, with a cam, ported heads, big valves, balanced, big carb, extractor exhaust etc etc. Lots of HP over stock. And, I wanted this car to be done right, with minimal risk of a bad transmission. So I called Jack Lawrence at MSS and discussed it at length with him. He asked me some questions about my assembly techniques, how I was going to set up the tolerances, and if I had a jig. The more I talked to him, the more I realized that there's more too it then just throwing in replacement bearings. Plus, he has the eye and the experience to REALLY KNOW when a part needs replacement (like a synchro) and has plenty of spare parts to pull from. His discussion on the internal needle bearings and how they fail and what to look for was fascinating. On and on he went, talking about his improvements over factory specifications, techniques, and parts. So, off it went to Jack for a real rebuild by a pro. He replaced every bearing including the needle bearings. He shot-peened the R&P and remachined the pinion surface. Cost was $500 in parts, and $600 labor. I'm very happy and expect it to last a long time, even with the increased HP.
My '68 Deluxe came with a noisy gearbox- a big whine! This past vacation, I tore apart 9 spare gearboxes that I had in a pile, to find one good one. What an experience! And boy did I learn alot and see alot of junk! I found one, maybe two good ones. The best one turned out to be a Sonett gearbox (ratio is 9:42 on the R&P). I've disassembled it to some degree, cleaned it, checked it, and nothing seems to be wrong. No evidence of bad bearings, the shaft nuts were tight, sychro's are okay, and the R&P backlash is acceptable. You know what? I just don't have a grand to put into it. So I ordered fancy heavy duty shaft nuts from Jack and yesterday I installed them using his techniques. Next, I'll shim the back cover to his specs, borrowing a depth gauge from work. I've refurbed a bell housing by cleaning up everything, especially the throwout mechanism which often is bent or rusted or just plain worn out. I have a 6 roller freewheel to install- yes, I insist on FW in this car. I drive it gently and its part of the character of the car. Will also install new seals for the driveshafts and main drive. All this is done with normal mechanic's tools and no fancy jigs. I did make a plywood holder to mount the trans/bellhousing to, so its held down when I tightened the pinion shaft nut- lots and lots of torque on that one! So I'll take my chances, cross my fingers, and hope it will come out okay. I told Jack what I was doing and there was 30 seconds of silence on the phone and he finally said "I don't condone what you're doing. But its your time and your car." And that's the point.
A couple of other points of advice.
- Take your time.
- Read, reread, and read again the manuals.
- Practice on a junk unit if you have one. Take it apart and put it together again. Get familiar with it!
- Phone a friend, ask the audience, or know when to cash in.
- Think about what you're gonna do if you have bad parts to replace, other than bearings. Do you have a donor gearbox or two?
- How will you press in new bearings without ruining them?
- Make darn sure you do the right thing with the shaft nuts! See Jim Williams sight (Sonett Saga).
Finally, its a personal decision- you have to weigh your abilities, cost, time, how the car will be driven, etc. If everything goes right, and the gearbox isn't toast to start with, you should be just fine!
I hope this gives help and encouragement!
Eric in Vermont
PS- I can't stand it! I have to add this one last thing. The shaft nuts. When you take apart your gearbox, see how loose they are. If they are finger tight or less (very common), this could mean your R&P are too worn to make it worth a rebuild. The gearbox wears, the nuts loosen, the gearbox wear accelerates, the R&P wear, the nuts loosen, then one day KER-BLAM and it explodes. So check those shaft nuts- its a first indicator of how bad things could be. Okay- I'll shut up!
posted by 68.142.42...
, Mon, 10 Mar 2008 14:43:35 <-- Viewing This Message, Wed, 12 Mar 2008 17:27:27, Thu, 13 Mar 2008 06:37:26, Tue, 11 Mar 2008 17:04:24, Wed, 12 Mar 2008 05:35:29
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