I am working on installitn a Ford 9in - I am using 4.10 gear Auburn Posi 10 bolt with my current setup

Its not likely I will change 700R4 any time soon - but if I do I am going to a TH350

I was wondering how much success people like IHI are having with 4.11 gears if I should stay with 4.11 for my combo or step down (up) to 4.30 gears

I currently run a 355ci with 150 - 175 hp NOS - which combo is not likely to change - save for pushing for more N/A runs and perfecting my tune - but car has been lightened significantly since my sig's best time

Have no new times as yet - but I am definitely looking for 11.00's in future

what do you think - stay with 4.10 (4.11) gears with the Ford or go to 4.30 and have more potential for n/a runs in future?

 

My 5 speed is taching 6200 @ the 1/4 mile with 4.10 and a 26" tire and is in 4th gear. If your gonna spray it then I would go with a 3.50 gear or maybe lower. But if your gonna run N/A most of the time then its probably gonna be trial and error to see what it does.

 

Here are my thoughts. Seeing as you are running an automatic transmission I would look into the Australian nine bolt with say 3.73 gears. These were available on 3rd gens from 1985 to 1989.

They weigh less and there is less of a horsepower loss. Plus they will bolt right in. If you get the right one it will have the big disc brakes on it already. Also TA has come out with a cover to support the spider gears and give it even more strength.

Something to think about.

 

I have a 9 bolt and love it

It all depends on your setup. You want to cross the line near your peak power, so If 4.30 gears (very steep) will get you there, then why not?

 

depending on how hard you spin your motor, but i would stay with the 4.11s. if you spray your car it will like the taller gear. remember nitrous makes alot of torque it can easily pull that taller gear. this is just my .02

 

I appreciate all the replies -

It has got me thinking that I have to take a hard look at my - well basically- stock short block 355ci combos- I have one in now and two spares - will hold up with higher rpm's brought on by 4:30 gears

I willl use the rpm calculator and see how future intended changes to 28x9x15 push my rpm's - and let that determine my position

Thanks all for the input

 

what did you have to do with the drive shaft..longer, shorter or the same????. and did you use the big ford ujoint??????

 

If your already running 28" tires, a 4.11 will be a well rounded N/A tire/gear combination. Should you decide to spray you will need either a taller tire or less gear since your rpm will increase ALOT when on the bottle.

Last thing you want to to run out of gear/cam. Would probably recommend a 3.73 gear with the 28" tire to achieve the best of both worlds. As with any combination, especially power adders, there has to be a line drawn somewhere between having your cake and eating it too. If your set up optimum for juice, your N/A will suffer a little bit, but that's just how it is.

I know with mine 4.11's/28" tire I shift at 6K and trap at 6600....I dont have anywhere left to go with this set-up as badly as I want to juice. I do have a few sets of 29.5" slicks in the basment that dropped me 700rpm compared to what my 28" tires trap at. 6600 with 28" 5900 with the 29.5" tire.

Your cam specs indicate it's not a top end breather/high rpm charger, it may feel like it's still pulling, but i bet when on a engine/chasis dyno once your up over 6K the power starts to plateu or drop slightly. You have more of a midrange spec and should gear accordingly to get the best benefit for your combination.

 

Jim, I have not yet gone to 9 inch - I scored a third member with aluminium spool from a fellow drag racer and so I have decided to get it rebuilt - and order a housing/axle package to fit spool and car - will get a 1350 yoke for shaft once I go there - and if I go TH 350 - 6 inch - I will have to use a donor longer d/shaft


IHI - with the 700R4 I am currently using 26x8.5-15 - slicks - and 4.10 gears and I am trapping in the high 6700 - 6900 - and thats with the 150hp NOS pills -

since I did over tranny with manual v/body and had my 10 inch comp. converter freshened by TCI and added a notch to the stall -and lightened car I am not going through the traps over 7000 like before

Its this combo before I shelled out car that borught my best time to date in sig

Thats why I felt if I went to a 28inch tyre that I would consider 4.30 gears - as I am trying best of both worlds

You are right about my cam - its a short oval grind for mid range torque but its rated for up to 7500 - and it goes past 7000 if you let it all to easily

I will probably get to try the 28 inch tyres with my current 10 bolt 4.10 gears for a comparison on trap speed and rpm's

before I install the 9 inch - so I will log and see how that plays out

Thanks

 

When the 4.11 geared torson takeoff diff. destroyed itself we went with 4.30 for brackets with a 350 2 bolt flat tappet motor. Our thinking was that the extra ratio would help offset extra weight from 9 " conversion. Worked fine. We have also gone from 28" tall tires to 29.5" tall tires and car hooks better, even if track is marginal.

You may want to keep all of this in mind if you plan on racing a lot.

 

L69/t5 with headers and exhaust ran a 14.5@95 on street tires and the stock 3.73 posi and 27" street tires...this spring before it exploded

i switched to a 9inch with 4.30s and a locker took my front sway bar and added 27x10.5 slicks... my 60' dropped 2 thenths and i ran a best of 14.430@96.66 in 90 degrees and 95% humidity..

i tach about 5grand when i cross the line in 4th gear...