Trans/gear ratio combo's - Chevelle Tech
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post #1 of 19 (permalink) Old May 30th, 19, 8:38 AM Thread Starter
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Durand
 
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Trans/gear ratio combo's

Right now I have a T-400 w/4.10's and have semi controlled minimal wheel spin.
General consensus around here is telling me to convert to a Glide w/1.96 low gear.


That would change the overall starting ratio to 8.03 from the 10.16 of the T-400/4.10's.
Couldn't a rear gear change act like a Glide and produce the same results with the T-400 using just 1st and 2nd for racing.( 2.48-1.48 vs 1.96-1.00 )
While having 3rd for better street manners?


The T-400 would have an overall low gear ratio of


9.25 w/3.73's
8.80 w/3.55's
8.48 w/3.42's
8.20 w/3.31's


Suggestions?

65 Pontiac Lemans 468 BBC, t400, 4.10 12bolt

Best 1/4 mile. 11.43 @ 118 mph
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post #2 of 19 (permalink) Old May 30th, 19, 8:50 AM
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Re: Trans/gear ratio combo's

I agree with your premise. The answer depends on if you just want to minimize wheel spin or actually make your car more pleasurable to drive at highway speeds. If the former, go with the 3.73s. If the latter, go to a 3.31. The lower (numerically) you go the more ET you’re going to scrub.

PS idealistically a 3.24 rear ratio would equalize the torque multiplication factor with the T400.

The reason I wouldn’t do the Glide is the rpm drop from 1st to 2nd makes your engine give up pulling power.

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post #3 of 19 (permalink) Old May 30th, 19, 9:17 AM
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Re: Trans/gear ratio combo's

Work on the suspension. No reason a t-400 and 4.10 should not hook. I ran a t-400 and 4.88's with a transbrake on small tires for years going 10.30's at 130. I would never put a glide in a car that heavy. My car had a t-400 in it for 22 years.
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post #4 of 19 (permalink) Old May 30th, 19, 11:23 AM
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Re: Trans/gear ratio combo's

Durand, is the car sub 3000 lbs. or running strictly 1/8 mile? Those seem to be the criteria for choosing a 2 speed. Otherwise, it simply doesn't make sense. Optimize the suspension to minimize spin and the 60'.


PS, you do realize that is EASIER to do wicked long burnouts with LESS gear, right? Adding gear typically reduces "burnout-ability". so, i challenge the "math" of the 2 speed crowd on that.

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post #5 of 19 (permalink) Old May 30th, 19, 11:46 AM
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Re: Trans/gear ratio combo's

TH400 and 4.11 12 bolt...


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post #6 of 19 (permalink) Old May 30th, 19, 7:07 PM
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Re: Trans/gear ratio combo's

Bill I tried to buy that car from I guess the guy you sold it to. I offered to buy it as a roller but no such luck.
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post #7 of 19 (permalink) Old May 30th, 19, 10:21 PM
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Re: Trans/gear ratio combo's

I don't race but just a thought: I have a 454 with 3.07's and a Truetrac and was always able to easily do burnouts. I got some Airlift coil air bags to lift the back end as I have a ton of stuff in the trunk. I lifted the rear end about 1" to 25 1/2" at the middle of the rear wheel trim. From the side, the tops of the doors are almost level to the ground. I can still spin the tires but it seems to hook and take off much better. I don't know if it is the height increase, or the increased stiffness the air bags provide. If it's the stiffness, it's marginal as getting groceries is just as comfortable as it was before.
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post #8 of 19 (permalink) Old May 31st, 19, 5:10 AM
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Re: Trans/gear ratio combo's

I went from 3.73 to 3.42,loved the reduction in gearing and didn't really give up any ET when running the 469". Had a set of 3.08's on the bench to install when had the 540" just never got around to it. At the end, I was starting out in 2nd gear and running it as 2 speed (2-3) with the 3.42's and 540 motor to try and kill power off the line to get the car to hook on 275/60 MT drag radials. Doing this got the car solidly back down into the 1.6X 60' range. Mark (Vortecpro) had urged me numerous times to pull more rear gear out and let the big motor do the work. Never got around to it.

3.42 x 1.48 = 5.06 ratio
3.42 x 2.48 = 8.48 ratio (was a crap shoot if it would hook or not, completely unpredictable)
3.08 x 2.48 = 7.63 ratio

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post #9 of 19 (permalink) Old May 31st, 19, 5:51 AM Thread Starter
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by Alan F View Post
I agree with your premise. The answer depends on if you just want to minimize wheel spin or actually make your car more pleasurable to drive at highway speeds. If the former, go with the 3.73s. If the latter, go to a 3.31. The lower (numerically) you go the more ET you’re going to scrub.

PS idealistically a 3.24 rear ratio would equalize the torque multiplication factor with the T400.

The reason I wouldn’t do the Glide is the rpm drop from 1st to 2nd makes your engine give up pulling power.
I was wanting some of both. and was thinking of going 3.55's-3.31's.

65 Pontiac Lemans 468 BBC, t400, 4.10 12bolt

Best 1/4 mile. 11.43 @ 118 mph
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post #10 of 19 (permalink) Old May 31st, 19, 6:04 AM Thread Starter
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by bracketchev1221 View Post
Work on the suspension. No reason a t-400 and 4.10 should not hook. I ran a t-400 and 4.88's with a transbrake on small tires for years going 10.30's at 130. I would never put a glide in a car that heavy. My car had a t-400 in it for 22 years.
The car actually works decent, but I do have 2 more things to do to the suspension. Lower control arm adjustment and front D/A shocks. Another thing that needs attention is the front/rear weight bias. ( she's a nose heavy pig ) I've had the T-400 in mine for over 35 years and am against swapping to a glide. I think the rear gear change would give better results.

65 Pontiac Lemans 468 BBC, t400, 4.10 12bolt

Best 1/4 mile. 11.43 @ 118 mph
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post #11 of 19 (permalink) Old May 31st, 19, 6:12 AM Thread Starter
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by 427L88 View Post
Durand, is the car sub 3000 lbs. or running strictly 1/8 mile? Those seem to be the criteria for choosing a 2 speed. Otherwise, it simply doesn't make sense. Optimize the suspension to minimize spin and the 60'.


PS, you do realize that is EASIER to do wicked long burnouts with LESS gear, right? Adding gear typically reduces "burnout-ability". so, i challenge the "math" of the 2 speed crowd on that.
She's 3500 lbs. and will be running both 1/8 and 1/4. I was thinking with the right rear gears I might be able to use 1st and 2nd like a glide for the 1/8, and have 3 gears for the 1/4 along with gaining freeway drivability.


PS. 3.08's in a peg leg are tire shredders with a big block.

65 Pontiac Lemans 468 BBC, t400, 4.10 12bolt

Best 1/4 mile. 11.43 @ 118 mph
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post #12 of 19 (permalink) Old May 31st, 19, 6:26 AM Thread Starter
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by GRN69CHV View Post
I went from 3.73 to 3.42,loved the reduction in gearing and didn't really give up any ET when running the 469". Had a set of 3.08's on the bench to install when had the 540" just never got around to it. At the end, I was starting out in 2nd gear and running it as 2 speed (2-3) with the 3.42's and 540 motor to try and kill power off the line to get the car to hook on 275/60 MT drag radials. Doing this got the car solidly back down into the 1.6X 60' range. Mark (Vortecpro) had urged me numerous times to pull more rear gear out and let the big motor do the work. Never got around to it.

3.42 x 1.48 = 5.06 ratio
3.42 x 2.48 = 8.48 ratio (was a crap shoot if it would hook or not, completely unpredictable)
3.08 x 2.48 = 7.63 ratio
I'm thinking gear change like Mark, and am debating on 3.55's- 3.31's.( I'll be adding some Vortecpro type power shortly and am forward thinking with the gear change)

65 Pontiac Lemans 468 BBC, t400, 4.10 12bolt

Best 1/4 mile. 11.43 @ 118 mph
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post #13 of 19 (permalink) Old May 31st, 19, 7:44 AM
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by LaVelle View Post
I'm thinking gear change like Mark, and am debating on 3.55's- 3.31's.( I'll be adding some Vortecpro type power shortly and am forward thinking with the gear change)
If that’s the case and you’re going to put a long arm in it, I’d drop to the 3.07 as Joe advises.

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post #14 of 19 (permalink) Old May 31st, 19, 8:19 AM
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by bracketchev1221 View Post
Work on the suspension. No reason a t-400 and 4.10 should not hook. I ran a t-400 and 4.88's with a transbrake on small tires for years going 10.30's at 130. I would never put a glide in a car that heavy. My car had a t-400 in it for 22 years.
I agree with Ray,

I ran a 427 with t-400 and 456 gears for years 28x9 tire with suspension tuning I got that combo to consistently run 1.46-1.48 60`s .

My current setup with same t-400 and 373 gears will run in the low to mid 1.30`s in the 60 with the same 28x9 tire


Brian

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post #15 of 19 (permalink) Old May 31st, 19, 10:52 AM
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Re: Trans/gear ratio combo's

Quote:
Originally Posted by LaVelle View Post
I'm thinking gear change like Mark, and am debating on 3.55's- 3.31's.( I'll be adding some Vortecpro type power shortly and am forward thinking with the gear change)
Talk to Mark about it. Street tires I was running a 265-60/17 (29.5" tall), could've even fit a 275/60-17 (30" tall) in there. All depends on where you want to run, bottom 11's don't need a lot of gear with a big inch motor, after that it's a matter of how hard do you want to spin it and how fast you want to go. Limiting factor becomes what you can get away with in safety equipment.

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