Author Topic: 3.73 gear install question  (Read 7706 times)

Offline 1976Scottsdale

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3.73 gear install question
« on: March 28, 2008, 11:18:37 PM »
This has been a while since I planned to do this to my truck.  I pulled my diff cover beacause my set of 3.73 gears got here.  My 1987 chevrolet R-10 has got 2.73 gears in it now, my question is, since my 3.73 set that I ordered are GM gears from a 87 suburban front axle, will they fit on the 2.73's carrier or do I need a new one of those now too?

Offline VileZambonie

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Re: 3.73 gear install question
« Reply #1 on: March 29, 2008, 08:19:59 AM »
The 2.73:1 carrier will work fine. I believe it's 2.56:1 and lower that requires a carrier swap.
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Offline Lt.Del

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Re: 3.73 gear install question
« Reply #2 on: March 29, 2008, 10:39:23 AM »
Take pics of you doing that swap if you have digital camera.  I'd like to rid my 79 of the 3:08 and put in 3:73 gears. How much did you pay for the gears?  A step-by-step tech page on the procedures you use would be really nice.

Offline bmaier

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Re: 3.73 gear install question
« Reply #3 on: March 30, 2008, 05:33:11 PM »
i second that SgtDel, i also have a 79. dont know my gears but i believe they are 3.08 and i also want 3.73's.
Are you just gonna lay there and bleed or are you gonna cowboy up?

1979 Chevy Bonanza K10, Shortbox, 350/350, 4" lift, 35's
1979 Chevy Silverado C10, Shortbox, 305/350

Offline DnStClr

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Re: 3.73 gear install question
« Reply #4 on: March 30, 2008, 10:01:35 PM »
Easier than counting gear teeth, The RPO code gives you the rear end ratio- if it's still in your glove box.
These are from chucks chevy truck pages website-
HE3- 3.07 ratio
HC8- 3.21 "
HC2- 2.76 "
HC4- 4.56 "
GT4- 3.73 "
GT5- 4.10 "
 
Don
87 Chevy Silverado

Offline VileZambonie

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Re: 3.73 gear install question
« Reply #5 on: March 31, 2008, 03:48:51 PM »
Setting up a ring and pinion isn't a huge ordeal but it has to come out right. Make sure you get a ring and pinion installation kit. This should come with a crush sleeve, pinion seal, cover gasket, shim assortment, and bearings. You'll need access to a press and a bearing clamp too. An inch pound dial type torque wrench (beam type will work if that's all you can get) and a pinion depth gauge. If you don't have a pinion depth gauge you can use a dial caliper and a few simple measurements. Get some good gear marking compound (gm sells the best stuff) and make sure you do a gear tooth contact pattern analysis. To aid in installing the new ring gear I usually stick the carrier in the freezer and set the ring gear in the sun or on a radiator to warm it up. Be aware some carriers have left handed threads on the ring gear.
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Offline lumpyokc1

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Re: 3.73 gear install question
« Reply #6 on: April 02, 2008, 04:18:26 PM »
im wanting to do the same switch, i have an 87 TBI and am getting around 16.5 mpg and was wondering what my mileage would be with the 373's i have 272's now any help would be appreciated.

Offline Blue 82

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Re: 3.73 gear install question
« Reply #7 on: April 02, 2008, 04:29:23 PM »
im wanting to do the same switch, i have an 87 TBI and am getting around 16.5 mpg and was wondering what my mileage would be with the 373's i have 272's now any help would be appreciated.

Drive around in "D" not OD for a week and see if your milege changes
(this would be approx equivilant to running 4.11's with .7 overdrive ratio)
82 stepside 2wd 355/th350/3.08 posi

Offline lumpyokc1

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Re: 3.73 gear install question
« Reply #8 on: April 02, 2008, 05:05:40 PM »
and would my mileage be a little better than that? since 373's are a little shorter than 410's?

Offline 1976Scottsdale

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Re: 3.73 gear install question
« Reply #9 on: April 02, 2008, 09:53:00 PM »
The swap is done.  The truck needs the TV cable adjusted but other than that its great.  It will darn near pull the front wheels off the ground.  It tooke me about 3 hours to do the job.  I had a press right there so it was no big deal.  I found a neat little printout on the net for the specs for installing a used set of gears.  BTW: I paid like 73 bucks for the set.  I did not need the press cause the set had the bearings on it and 30,000 miles.  I checked with all the guages and it was well within all the specs.  The freezer trick ate up the most time, works good though.  Oh yeah, remember guys, left hand threads on the ring gear bolts.