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Gear swap

Cwazywazy

Cwazywazy

Single jingle
Joined
Aug 20, 2016
Location
Granby CT
The turbo 240 cruises at 3000RPM at 70 in 5th (M47) and I'd rather give up some acceleration than have to live with that. I'm really not sure what's in it but I want 3.31 or 3.53. It has a powertrax lock right which I obviously want to keep. Can I just swap the ring and pinion from the '86? Assuming they're both the same axle.
 
Go for it! It's rewarding learning how to pull apart a rear axle.

Get a magnetic base dial indicator.
 
Probably not. I tossed a g80 into my 240 and used mismatched bearings into different outer races.


Backlash too much you will whine. Too little can burn up the gears.
 
There's no sticker on your axle indicating what ratio you have? If not, it fell off. I'd go 3.54. 3.31 is a dog.
 
centason said:
There's no sticker on your axle indicating what ratio you have? If not, it fell off. I'd go 3.54. 3.31 is a dog.
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I'll just use whatever's in the '86. M46, 6k at 60 in second. '88 hits 6k at ~55. IIRC the M46/7 are the same ratios except for 5/OD, right? Same size tires I think. Haven't even looked for a sticker yet.

I wonder if it used to be an automatic or if the gears were swapped. Trans definitely feels like it has 300k+ as the odo indicates, so IDK.
 
From the research I have done, automatic cars have a 3.73 rear gear and manual cars have a 3.31 rear gear. My 1991 with an automatic and the stock rear gears turns ~3000 rpm at 75. If you swap in a set of 3.73 gears out of an automatic car would INCREASE your rpm at interstate speeds.
 
VB242 said:
I can pretty much guarantee you will be disappointed with longer gears, turbo will not spool the same.
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Yeah, I'm still debating whether it's worth it. I love the way it pulls but I hate the way it cruises at highway speeds, and unless I get another car (Selling the 86 sometime soon) I'm going to be driving it on the highway every day in a few months.
 
ZVOLV said:
Probably not. I tossed a g80 into my 240 and used mismatched bearings into different outer races.


Backlash too much you will whine. Too little can burn up the gears.
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Is it really that simple that you can set up a rear end at home? I thought there were a lot of special tools involved? I've heard of guys paying like $600 - $700 to have a differential put together and gear lash set.
 
Kenunot said:
Is it really that simple that you can set up a rear end at home? I thought there were a lot of special tools involved? I've heard of guys paying like $600 - $700 to have a differential put together and gear lash set.
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In true TB fashion, Yes, It is that simple. People have had success just swapping things around and sending it.

Now, a proper rear end job at a shop, setting up shims, pinion depth, mesh and all, Yeah, $600 job.
 
I recently swapped my 84 to an AW-71L on the stock 3.54 1030 rear end. It was ok-ish, but once the lockup kicked in, it was almost undriveable at Canadian speed limits (62mph on the highway, and 50-ish on smaller roads) as the rpms were below 2000. I recently swapped in a 3.73 1031 and installed a G80 at the same time, and have to say it's quite a bit better. It would be very nice without the lockup function, but hey...it was all I had. I got my mileage down to 25mpg though, from 17mpg on the BW55, lol.

When I did the G80 swap, I made the mistake of using the races that came with the Timken bearings I got at a local bearing supply place. BIG MISTAKE. My backlash was insane! I couldn't figure out what I did wrong, until I compared the new races with the old. Yeah...the OG Volvo ones were bigger, and pushed the bearings inwards when installed. I swapped the races out, and the backlash came out to 0.005".

Also, the spool with the AW-71 (out of lockup, in OD) and the 3.54 was decent, but you barely felt it accelerate.
 
is it excessive sound that is bothering you?
If that is the case you could also invest in some additional sound deadening.
easy DIY stuff, way easier then setting up a set of diff gears

you need a torquey engine to pull tall gears and still have acceptable top gear acceleration
 
OP, swapping a complete 1031 rear end assy. will be MUCH less work and faster than a complete ring & pinion swap.

I've done several..... special tools and special skills are required. TBers are known to "throw parts together and hope", but it you want a quiet and reliable rear end, that will endure periods of HIGH torque application, there is no alternative to spending valuable time & resources to get it right (preload on pinion bearings, correct pinion depth into the hypoid ring, and proper carrier bearing shims/preload so that backlash is correct). Too tight, she burns up.... too loose, she whines like a banshee.

Save yourself the pain and "learning"..... swap a complete known good rear end assy. and enjoy a cold brewski.
 
DET17 said:
OP, swapping a complete 1031 rear end assy. will be MUCH less work and faster than a complete ring & pinion swap.

I've done several..... special tools and special skills are required. TBers are known to "throw parts together and hope", but it you want a quiet and reliable rear end, that will endure periods of HIGH torque application, there is no alternative to spending valuable time & resources to get it right (preload on pinion bearings, correct pinion depth into the hypoid ring, and proper carrier bearing shims/preload so that backlash is correct). Too tight, she burns up.... too loose, she whines like a banshee.

Save yourself the pain and "learning"..... swap a complete known good rear end assy. and enjoy a cold brewski.
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This is a good idea, but then I'd have to find and buy one.. And I'd still have to swap the locker.. Both cars are 1030, haven't gotten under and looked for a sticker yet.
 
FWIW my non lockup AW70 / 3.73 rear na 245 cruises around 3k on the highway also. Still gets the same 20 - 22 mpg it always does. I've made a number of 2400 mi round trips back home and it doesn't seem to give a **** cruising at 3000 rpm for 10 - 12 hours at a stretch.
 
Kenunot said:
FWIW my non lockup AW70 / 3.73 rear na 245 cruises around 3k on the highway also. Still gets the same 20 - 22 mpg it always does. I've made a number of 2400 mi round trips back home and it doesn't seem to give a **** cruising at 3000 rpm for 10 - 12 hours at a stretch.
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I drove from California to PDX on I-5 after my overdrive failed off. 4000rpm, burned some oil but otherwise was fine.
 
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