Goofy trans/gear combo?

[fanmanj]

Ok, my new truck has a 305/700r4 combo. I checked the RPO codes, and it has a 2.73 rear axle! The shortest gears I've ever seen with a OD trans were 3.08's... I could understand if the truck had a TH350. Anyone else have this? I bet it idles doing 70! And with the 160hp 305, I bet it's A real dog trying to take off..
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[N2TRUX]

And the irony of that sad combo is it was supposed to save fuel. Only problem is you have to keep your foot in it to make it go....

[lindstromjd]

A friend of mine has a '90 Camaro with a 305/T5 and the 2.73 rear end. Not much on the bottom, but cruising at highway speeds he could easily get 25+ mpg's. City driving really sucked though.

[sumran]

Was it configured that way from the factory? Or was something changed along the way?

[jitteryguy]

first gear in a 700R4 is low'r than a T350/400 so that help's some with take off, still may work against you in town but should be awsome on the high way.
you should take it to Bonniville and see what she'll do top end !

[b454rat]

The 84 I built couple years ago was ridiculous. Was a short box 4x4, 305, 700r, 2.73s and 31" tires all factory. It had a 350 in it when I got it, and was still a dog. Course didn't help any that the carb was screwed up and the 4 barrels didn't work.

[dgreen]

i got a 87 chevy with that gear combo but i got the 350tbi, its a dog

[rayfinseats]

Mine was equipped like that from the factory in 83. I have the spec sheet. Tht's because engineers think with formulas and math and have no common sense. I used to work in engineering. My nephew was an engineer/designer for Ford and never worked on a car in his life.

[fanmanj]

Yeah, being an ex-GM dealer technician, I can say engineers and designers suck.. These plastic bubbles they sell now have no "soul" to them.. And they're hard to work on! That's why I bought my '86.. The last REAL truck built by GM in my opinion is this body style.
I may only be 24 but I am a connesieur of old stuff. I believe nothing worth a damn has been built in the last 20 years.. It's all throwaway plastic crap!!
Ok... I vented lol. *steps off soapbox*
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[68longhorn]

my 86swb also has the 305/700r4 and 2.73s. Great on the highway for up to 18mpgs. Its a turd but will haul a truck of mulch without much problem.

[78 Chevyrado]

I had that combo in my 87. It was a total dog until I put a 400 in it. Then it got great mileage on the freeway.

All I can say is don't tow with it or you'll likely blow up your spider gears. Mine broke (10 bolt, 2.73) towing an empty 1000lb trailer and trashed the axle and trans completely.

[mooseknuckles]

700r4's have a real low 1st gear, thats whats great about them....my 86 has a 305/700r4, I'm not sure of the rear gears, but it hauls ass for a 305..its no 350 but not bad...

[LONGHAIR]

Believe it or not, there is one worse. That same enging/transmission combination was available with 2.56 gears.....and 4 wheel drive.

Back in the early 80's a friend of mine's dad had one....flaming dud.

[GM 4 Life]

My 87 2wd had the same combo. My 305 and 700r4 are both freshly rebuilt, with the 700r4 being beefed up some and it was still a total dog! Then i switched to a 3:73 gear and now she will get a 2nd gear scratch taking off in drive with half throttle. Night and day difference. I do have to be real cool in wet weather now taking off. Btw, gas mileage sucked on my junk so the gear swap was a no brainer. 2:73 = GEAR SWAP!!

[Gearhead1]

I've monkeyed with gear ratios for 40 years. The problem is that the engine is too low on the torque curve, and the truck is shaped like a barn door. If you can sneak up on a cruising speed and maintain a steady throttle foot you can get repectable mileage on a smooth flat road. But if you have to change the throttle for any reason, the mileage goes away.

A long time ago I went from a 3 speed with a 3.70 rear gear to a 3 speed + overdrive and a 3.55 gear. Top speed stayed the same, mileage stayed the same and the acceleration was noticably worse. Changed the gear back to 3.70 with overdrive, mileage increased, top speed increased and the acceleration came back. All this in a 'jacked up' 55 Chevy.

I now have Crew Cab with a quick change. We'll see if a 454 likes the 3.65 I have in it now or ????? It won't fry the tires like the 4.56 did but i can always put in my 8.30s if I want to do that.

[INSIDIOUS '86]

i had a 305 with the 2.73 gearin my 86 shortie, i spent months working the stock motor to make it run like hell like taking off a/c and smog an p/s, got rid of the cat and threw on headers and purple hornie dumps. i would go about 70mph on the highway at idle! haha. i would get about 18-21 mpg on the highway easy, if i wasnt dropping it to 2nd to put some honda in its place lol, bit i still cant wait till the 3.73 gears come!

[gchemist]

The stock configuration on my 83 had 2.72 gears. 305, 700R4 and stock tires. Silverado package. I swapped the axel for a 3.08. With mods, it could manage 18.5 MPG at 70. Funny, same as my current ZZ4!!

[thirdstreettito]

That rear end would work with an SM465 and small tires.

[84SierraClassic]

Posting for reference and possible helpful info for future searches.

I have a '84 GMC SierraClassic. From the factory came with 305/700r4. I'm not 100% certain in rear axle gear, but from what I can find based on the numbers, I have a 2.56 positraction. Numbers are BB3 G040 2. Corporate 10 bolt. RPO code is GQ1 (yea, that's a code that doesn't exist) with a description of Rear Axle -Standard.

I tried jacking up the rear end, put truck in neutral, and spin drive shaft. Came out as a 1-1. 1 driveshaft turn to 1 wheel turn.

Truck now has a 350/700r4 same rear end. No tach installed yet so not sure of cruising RPMs but it's a friggin dog once it hits final gear, barely chuggin along.