73-77 monte/chevelle rearends the same?

by fishhead Fri Jun 21, 2013 10:32 am

Is this a direct swap? Also,did most 77's with 305's usually have lower gears in the rear? Thanx.

by driveit Fri Jun 21, 2013 10:39 am

Believe so. No issues between the two If I am not mistaken.

by dynchel Fri Jun 21, 2013 11:19 am

I think '77 started using a 7.5 rear end, maybe not on all cars, but I know at least some had 7.5's (instead of the more durable 8.5) so watch for that. Beer

by driveit Fri Jun 21, 2013 11:26 am

Good point dynchel, you have always had good advice since I joined!

3 cheers!

by dynchel Fri Jun 21, 2013 11:37 am

I've been researching / working on my '74 for the last 19 years, so a lot of this stuff I've already went through.

by thatfnthing Fri Jun 21, 2013 11:44 am

Gear ratio was a function of the transmission, not the engine. The 3 speeds (TH350, TH400) topped out at 1:1, so your choices for rear gears were like 3.08 for performance and 2.73 for mileage. Any higher and you wind up with overly high RPM's on the highway. Once the 4 speed OD transmissions (TH200-4R, TH700-R4, 4L60, etc) came into play with a top gear of like 0.67:1 or 0.7:1, then you could get higher rear gears like 3.42 or 3.73 without over-revving the engine.

by dynchel Fri Jun 21, 2013 11:54 am

thatfnthing wrote:Gear ratio was a function of the transmission, not the engine. The 3 speeds (TH350, TH400) topped out at 1:1, so your choices for rear gears were like 3.08 for performance and 2.73 for mileage. Any higher and you wind up with overly high RPM's on the highway. Once the 4 speed OD transmissions (TH200-4R, TH700-R4, 4L60, etc) came into play with a top gear of like 0.67:1 or 0.7:1, then you could get higher rear gears like 3.42 or 3.73 without over-revving the engine.

I know the scenario I have a th350 with 373 gears. Mad

does good burnouts, pulls real strong off the line.....but definatly not a freeway car.

by Joe73 Fri Jun 21, 2013 4:29 pm

Both rears are the same mounting wise, so either will fit. I did find that the monte rear is about an inch to and inch and half wider than the chevelle rear. So watch your rim offsets.

My chevelle came stock with a muncie (1:1 final drive) and a 3.42 rear. It ran about 2200 rpm on the highway. My current 4.10's are useless on the highway. LOL.

by alleyball4 Fri Jun 21, 2013 6:41 pm

thanks for all the feedback ...

I have a Muncie 4 speed, and will have a 3.42 rear with it.

by JB2wheeler Fri Jun 21, 2013 8:32 pm

I have a 400 trans with a 3.42 rear ratio and 27.1 inch tires and I do a roaring 3,000 RPM at 60 MPH. JB

by DiscoMalibu Sat Jun 22, 2013 9:29 pm

Hate to mess this up but I've been wondering... I just stuffed a Saginaw four speed in my '77 with a 3.08 rear. How's this thing going to be on the highway? I'd imagine it'd run a lower RPM on the highway than the 3.42 setup, no?

by Pontichev327 Sat Jun 22, 2013 10:06 pm

Your final drive ratio is still the same as with your automatic...1:1. Highway cruising no problem. Should be a fun ride around town!

by Pontichev327 Sat Jun 22, 2013 10:09 pm

The 3.42 setup would have more low end grunt, but would rev a bit at speed, it depends on what you want to do with it, and how you drive.

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73-77 monte/chevelle rearends the same?

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