Engine and Transmission Tech

From what I understand they make a wide ratio and regular.
Running 3.73 limited slip and a Ford 302 , should I try to find a wide ratio ?
I would like to hear your opinions but I would like to know why.
Thanks Will

I like the wide ratio for forced induction. Well I don't have any experience with supercharging but I have seen good results with using one for turbo charging. On our challenge car (rabbit 16v 1.8t) we used a VW diesel transmission for the wide gears. It gives more time for spool.

If it's economy you're after then you could just swap out the overdrive...

Thanks Nicolas,
Running a 302 Ford normally aspirated, but what I was wondering, was would this help me not run through the gears so fast as everyone seems to say will happen with such a high rear gearing, as I am running 3.73 . Will someone chime in that might know the effect this might have and if it would be worth the trouble?
Thanks Will



Edited 1 time(s). Last edit at 10/19/2009 10:03AM by B-Fast B-Strong.

Hi Will,
depends on what your objective is with the car and also if you plan to modify the 5.0 from standard.
Bernard.

Welcome to the forum, Will!

Your decision should be based on the power characteristics of your specific engine. If you had them, you'd work from engine dyno results. Next best thing? Do you know much about your camshaft? Your camshaft manufacturer should be able to tell you where the engine will make peak power and also how wide the top of the curve will be. If your gear ratios are too widely spaced, each time you shift to a higher gear, your engine will fall too low on the curve, slowing your rate of acceleration... Once you know what rpm range you ideally want to stay within, you can make gearing decisions based on a gear calculator, like this one:
Dan Masters' nifty calculator for gear comparisons (Microsoft Excel)



Edited 1 time(s). Last edit at 10/19/2009 12:03PM by Moderator.

William there are lots of different gear combinations available for the T5. What is commonly refered to as a "wide ratio" box would have a lower first gear with wider spacing between the gears up to 4th and then most likely a shorter overdrive ratio. These boxes were usually used in the smaller engine displacment applications where the additional torque multiplication at start was needed but the engine didn't have enough power to pull the higher over drive ratios as the V8 boxes. Running a 3.73 rear gear I'd say that you'd be better off with a V8 type box with the higher first gear and higher overdrive ratio. Even with the V8 trans you'll probaby find that you run through first very quickly with the 3.73 diff. There's a good list of available ratios for the T5 in the newsletter archives at [www.britishv8.org] . I find that figuring out final gear ratios, engine speeds, and vehicle speeds is easy using this on line calculator designed primarly for the F body GM cars but useful for any others if you know the transmission ratios. There are a lot of transmissions already listed in the menu so you'll probably find one that matches your needs there already to compare with. [www.f-body.org]

Engine is HO 302 roller, changing heads to alum. and was going with 5.0 mustang 3.39 4.03 2.37 1.49 1.00 0.86 and the 3.73 rear end. I think that will serve me the best. I was just wondering with the car being 2000 lb if there was some advantage to a wider ratio. It is my understanding this engine has a killer mid range.
Will



Edited 1 time(s). Last edit at 10/20/2009 10:21AM by B-Fast B-Strong.

Looking at that list I don't see any with a wider ratio.

I have a few questions to ask:
(1) Does the shifter come out in the right place?
(2) Will the B's master drive the slave?
(3) Are there any got ya's I need to know about?

Thanks for all the help guys,
Will

The T5 fist gear 4.03 ratio transmission you mentioned is used only in Ford 4 cylinder cars. You will have problems with using it with a V8 clutch and bell housing. The input shaft will be a little long and the pilot bearing diameter on the shaft will be to small to work with a V8 pilot bearing. Even if you got it to work I don't think you would like it unless you run a 3.08 or lower rear end gear. The 4.03 first gear with a 3.73 rear end will have you looking for second gear almost as soon as the car starts rolling. I ran a 4.03 with a 3.89 rear end gear and that is what I experienced. I think you would have a hard time telling the difference between any of the Ford specific V8 T5s that are out there. I am running a turbo charged 4 cylinder with a 2.95 first gear T5 and 4.11 rear end gears and it works well for me. The 2.95 fist gear T5 is a Ford Racing aftermarket item for the v8s so you would have some trouble finding one used. Any of the production 3.xx first gear T5s will work fine in my opinion. The v8 T5s also have a better OD ratio.

Ford 1983 SVO Mustang 5.0 V8 C code 3.39R 4.03, 2.31, 1.49, 1.0 , 0.86

You are thinking GM they have a 4 banger trans with these ratios.

Here is my problem , I have not thought about ratios in a long time and I just can't get my head straight.
This is what I call a wide ratio tranny . I am thinking I may need to find as close a ratio as I can find to do what I want not as wide as I can find ,but I just can't get my head straight. I will be running a 3.73 rear and I want to be able to wind first out , not have to jump right out of it, the car is light, don't need help getting out of the hole.

Ford 1992 5.0L Mustang WC Y code 3.15R 3.35, 1.99 ,1.33 , 1.00, 0.68

This may be what I really want with the 3.73 rear, won't this let me wind first out and give me the highest top speed, I guess I need to find a ratio calculator and see what the speed at 6000 rpm would be for each.

Ok !
I went back and read all the post and I have my head straight now,
I need to find a close ratio with a final ratio that will get me the highest speed .
I don't have excel so I could not use the calculator so could someone tell me what the 0.68 with 3.73 rear running 235-50-15 tire . speed at 6000 rpm would be ?

Thanks Will

Theoretically, 170 MPH

Use this site to play around with the numbers...you don't need Excel:

[efi.moonwell.com]

-- Scott

With those tires and a 3.73 rear end gear the 3.35 first is what you want because of the .68 OD. On the open road you will be at about 2,000 RPM in OD. Right where you want to be. If your building a racer then the OD makes no difference.

Ford also has 4.0 first gear T5s. I have a couple of them. The OD ratio in the 4 banger trans is .87. That OD ratio drove me nuts listening to it on the open road but then maybe I needed better mufflers.

Thanks yall ! I thought I had it all worked out and about 170 was what I was guessing, like I am going to get there.
I had my 280ZX Turbo about 160 one time and it was getting a little light, don't care to go there again. I don't mind going fast just like being in control.

First, you want a T5 that will hold up to the torque that your going to produce. With the light vehicle, it should be less taxing to move the car and thus more forgiving to use a lower torque rated T5.

Okay, if your happy with the torque rating given... Lets say you find a T5 with a 3.35 and a 2.95 1st gear. Either one can have the 5th gear changed out but they are both usually placed in a generic good location for the rest of the gears and the correct rear axle ratio for that car.

Continuing on, If you have a stock cam or a cam that gives good torque through a wide power band, a WIDE ratio is generically better where if you have a lumpy race cam, narrow is generically the way to go.

The rear end should be geared to the camshaft (which is usually chose to fit the engine build) and the gearbox in the middle placed to match the engine and differential. For a wide ratio on my conversions, I like the 3.42 GM rear or maybe a ford 3.5. You can go around a 3.2 ratio rear end and still have nice gearing. 3.0 to 1 is a bit high but certainly better than the stock 3.909 for just about any conversion.

Lastly- I know little about the overall feel of the 302 so i have an idea based off theory but no practical experience with that exact engine. Still, I know my basics so use this information as you will.

10 years ago there was almost NO talk of the wide ratio 'boxes vs. narrow. People just followed what was normal behind the V8 engines so compared to the various engine conversions the idea of the wide vs narrow is not considered as much. You will see only around a 5% increase in usefulness. Will you notice? Only if you drive a couple cars afterwards for comparison.

-BMC.

Thanks Brian,
I know you have done a lot of V6 swaps and I value your opinion . It has been a while since I did any racing and I was having trouble getting my brain back in that state of mind. I am making a real hot rod , almost like a race car driven on the street. I am building a 302 Ford , dry sump , normally aspirated , 400 to 500 hp. I will be putting a Tremec 5-Speed T5 Transmission Gear Ratios: 1st 2.95, 2nd 1.94, 3rd 1.34, 4th 1.00, 5th .63, Reverse 2.76 from Jegs behind it. It is a built up heavy duty tranny they use in the hot Mustangs I will have a 3.73 limited slip rear end , composite leaf spring .I will be fabricating a pan-hard bar, traction bars and gas shocks. In front I will be building tubular A-Frames and coil-over shocks off the stock cross member after I hack it up a bit.
Regards Will

I beleive you made a good choice. That is the same T5 that i have in my car and the 3.73 will work well with that trany.

Yup. For the engine your building, narrow ratios, low (speed) rear end is what you want. Keep in mind that the T5 is only supposed to work with up to 300 Lbs Tq but in a light car should be okay. Your certainly going to be taxing that a bit though. I'm certainly not the guy to talk about what you can build for a street car but 400-500 BHP will require flares (for traction) and a complete body kit which we just happen to sell. :-)

-BMC.