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Here’s what I’ve learned about differentials:
Thanks to the Brickboard I’ve gotten a lot of good advice about what to do with various repairs to my old ‘82 wagon (DL M46, 245K). Lately, I’ve been trying to deal with a chronic noise coming from the rear end. All the bushings have been replaced as well as the axle bearings, so I suspect the pinion bearings if not the ring and pinion gears. It seems that low mileage boneyard rear ends with the ratio I need are pretty scarce, so I’ve been curious about the possibility of repairing my own.
Trading Ratios
I’ve found that this is a repair that you could probably do yourself, given access to a few special tools and plenty of time to pay attention to the right details. I’m not suggesting that it would be easy, only that it is something worth considering. Details to follow.
What I’ve also found out is that there are boneyard rear ends out there that might work for my car, if I consider changing to a different gear ratio. It seems that the last cars with my 3.54 ratio were some ‘84 models. The automatic models from ‘85 through ‘93 had 3.73:1 rear ends, and there seem to be a number of them in the yards. I’m thinking I might be able to live with that slightly higher gear ratio.
The effective difference between ratios 3.54 and 3.73 amounts to about five percent (5.36 percent, using the technical note “myths” at ringpinion.com, Randy’s Ring and Pinion). I’d gain a little in power to the wheels and lose a like amount in fuel economy or range per tank. Let’s say that with the change to 3.73 I’d get five percent more get-up-and-go but only be able to get 95 percent of the way there.
With a light load and mixed driving without AC, I now get about 26 mpg. If I make the change to 3.73 I might get 24.6 mpg (94.64%). A typical trip for me is about 330 miles and the gas for that trip today costs about 38 bucks. The same trip with the higher-ratio rear end would run about 40 bucks. The trip would seem to take longer too, as when I’d be cruisin’ at 70 mph, the speedometer would only read about 66. (And when the speedometer read 70, I’d actually be going 74, well toward eatin’ up a state trooper’s grace margin for speeding.)
Let me know if you think I’ve missed something.
Do It Yourself
And here’s information about doing the differential work yourself, including large parts of earlier post:
There are a number of sources with Internet sites that deal with differential repairs and upgrades. Many are aimed at the jeep/off-road market. I happened onto one that also lists parts for Volvos. It’s Randy’s Ring and Pinion in Washington State [ringpinion.com]. Here’s what I found out today:
· Volvo 240’s are equipped with “Dana 30” differentials;
· Repair of Dana 30 differentials do not require the use of a housing-stretcher tool, while repairing the larger Dana differentials may;
· Information on their web site will help determine whether the ring and pinion gears need to be replaced (visible loss of metal, grooving, chafing of gears, metal in fluid), or just the pinion bearings;
· They stock OEM and after market gears in all four ratios used in the 240s, and also can upgrade to a limited-slip;
· Printed instructions come with their kits, and a video is also available and may be included in the sale, tech library available online;
· Special tools needed to perform the differential work are: 1) an inch-pound torque wrench (not “click type”), 2) dial indicator (machinist’s tool for measuring backlash), 3) hydraulic shop press (to press bearings off and on pinion shaft);
· Before work could start on the differential, other mechanical stumbling blocks would have to be overcome. The first would be getting access to the differential. I suppose the job could be done with the rear end in the car, if you raised the car enough and lowered the rear end even more than usual by disconnecting the lower shock bolts. The rear brakes would have to be removed and the half shafts would have to be backed out, and the pinion shaft flange would have to come off. Counter-holding the pinion flange could be a challenge.
Here’s a rough summary of the prices they gave me over the phone:
· Pinion kit (both bearings, shims, marking compound, instructions) $80.00
· Ring and pinion gear set (ratio 3.54) $142.00
· Installation kit for gear set above (all bearings, shims, seals, bolts, etc.) $110.00
· Inch-pound torque wrench (for rotational measure) $58.00
· Machinist’s dial indicator, magnet base $49.00
· Limited-slip upgrade (complete carrier) $350.00
Randy’s Ring and Pinion, ringpinion.com, 800-298-9541, 425-348-9002 tech support
While I’d still like to find a good, low-mileage rear end, this information leads me to believe I could take it on myself with a pretty good probability of success. And I am intrigued by the prospect of doing it myself. When you consider that a housing stretcher does not need to be used and so the project could be done while the rear end is still in the car, redoing it myself with new parts might be a lot less work (?) than finding a decent one in a boneyard and swapping the two. The end result might not be much different, but maybe just a little more satisfying.
Anyway, that’s how it looks so far. Thought I’d pass it along. If you have any insights into the big quagmires of this project which I’ve overlooked, don’t hesitate.
As always, thanks again for all your generous help.
Steve.
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