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02-11-2021 #1Registered User
- Join Date
- Jun 2009
- Location
- Bangor, Northern Ireland
- Posts
- 43
Rear gears - 3.25 or 3.40 gears to replace 3.73's. '69 Camaro with Ford 9"
Hi guys
My Dad's pro touring 383 '69 Camaro is waiting for its SBC 427 to be installed. We're discussing trans/rear gear ratios for it.
My 383 '69 Vette has a TKO600RR (2.87 1st .82 fifth), 3.55 gears. It's lovely to drive, but we will change gears to 3.36 where it will be perfect.
The Camaro has a TKO600 (2.87 1st .64 fifth), 3.73 gears. It's horrible, 1st is borderline pointless, 2-4 are over in a flash, then you're into 5th where the car dies on its ass.
The .64 trans is not a good ratio for cammed cars, people use the 3.73 rear end ratio as a compromise so that you can get into fifth at a reasonable speed, but at the expense of 1-4 being too close. This creates a car that is never in the right gear IHMO.
....so we've decided to lower the rear gears to make the most out of 1-4, were not fussed about 5th, the only time we'll use it is on the motorway at 70+, so if we can't use fifth below that speed then that's fine. It's worth it to get a good 1-4 spread which is 98% of driving.
Here's the engine -
https://www.tristarengines.com/perfo...cylinder-heads
So my question is, which rear gears? (Ford 9"). Both cars are driven hard.
A - 3.25's, my choice
B - 3.40's, my Dad's choice
Any advice appreciated
Cheers!
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02-11-2021 #2Registered User
- Join Date
- Mar 2020
- Posts
- 199
To be clear, I'm assuming you mean driving at part throttle. This, I can understand as you have a very deep first gear & the jump between 4th & 5th is huge.
Your trans (.64 5th) is mainly meant to be used as a 4 speed performance trans that will drop the rpm on the highway.
I would not anticipate a shift to 5th under power as it drops the RPM too far.
The .82 5th has a good spread that allows you to use 5th as another gear while driving.
The ideal rear gear depends on the ability to lug the engine due to cam etc.
I currently am running a T-56 Magnum with a .63 6th & 4.10's. I can drive it about anywhere in 6th over 35mph... but I have another gear (which happens to be a .81) between 4th (same 1:1 as your 4th) & my 6th gear.
I also think the 5 speeds have too wide of a spread 1st thru 4th.
You never stated your tire height so it is tough to recommend a rear gear, but I never think about less than a 3.55 or 3.73 in a performance car... unless it is strictly for highway or top speed runs.
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02-12-2021 #3