Transmission and gear ratios

[Scott S.]

18 minutes ago, BobW said:

So I guess I answered my own 'dumb' question! Put the MC in 2nd and it did shift from 1st to 2nd, presume the 200r4 will do the same.

Stopped to fill up after this morning's cars & coffee and calculated mileage at 13.3! This tank had mostly 1 to 2 hour runs at 50 to 70 mph. I think I could have safely been in OD for 80% of those miles.

Pretty sure I'll eventually do the trans swap and shift as needed.

That's not to bad for mileage in 3rd gear. (1 to 1)

Mine runs about the same, so with the 0.67 to 1 overdrive, you should be able to get about 17-18 miles to the gallon..... 

Keep in mind, American gallons are 3.8 liters whereas Canadian gallons are 4.55 liters, so one can go farther on a Canadian gallon.

[BobW]

1 hour ago, Scott S. said:

Keep in mind, American gallons are 3.8 liters whereas Canadian gallons are 4.55 liters, so one can go farther on a Canadian gallon.

Well familiar with Canadian gallons. I rode my motorcycle from Florida to Hyder, AK, only reachable via Calgary to Stewart, BC. Canadian Rockies, beautiful country!

[sbarnette]

On 1/21/2023 at 1:45 PM, Scott S. said:

The '84 I owner came with 3.42 to 1. As did the '86 T-Type. They must have dropped the ratio on the Montes in '85-'86. 

I don’t remember, did the 84 Monte SS have a overdrive transmission, or was it 3 speed. 85 and 86 had overdrive and 3.73. I’ve owned this one since Dec. of 86. She has a little over 50,000 miles now,

[Scott S.]

'83 & '84 had a 3 speed, '83's had a split bench seat as well. The 4 speed in '84 was an option that became standard in '85. 

[cbolt]

On 1/23/2023 at 6:11 AM, sbarnette said:

I don’t remember, did the 84 Monte SS have a overdrive transmission, or was it 3 speed. 85 and 86 had overdrive and 3.73. I’ve owned this one since Dec. of 86. She has a little over 50,000 miles now,

Beautiful car Sammy. My oldest son wrecked mine unfortunately but before that it looked just like yours but with the T-top option and had roughly 50K miles on it. 

[BobW]

On 1/20/2023 at 12:02 PM, BobW said:

I think you hit the nail on the head!

Found a post that listed final drive gear ratios with RPM's at 70mph. 273's at 70 would be running at 1800 RPM's.

This post related to the swap with a base 350 like mine. OD kicking in at 45mph would severly lug the engine. A high torque stroker motor 'might' pull the higher ratio better.

General consensus from that discussion felt 308's would be the highest acceptable ratio, with 331's most likely the best compromise for performance and economy.

Now my mind wonders if a non locking converter would function OK, or just shift in and out if OD?🤔

Still overthinking this swap! I used a calculator (https://purperformance.com/p-29669-rpm-calculator.html) to figure RPM at different speeds.

With my 27" tires OD at 70 would drop from 2400 to 1600 rpm. 

OD at 60 would drop from 2040 to 1365 rpm.

OD at 55 would drop from 1870 to 1250 rpm.

OD at 50 would drop from 1700 to 1140 rpm. 

Would the 1250  or even 1365 rpm be too much lugging, use more gas and potentially harm the engine?

 

[sbarnette]

12 hours ago, cbolt said:

Beautiful car Sammy. My oldest son wrecked mine unfortunately but before that it looked just like yours but with the T-top option and had roughly 50K miles on it. 

Thanks Jim. I remember you telling me about that at the Eastern Meet in Bristol.