Steep rear end gears (4.10s) compensated by replacing overdrive in a T5?
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I did that years ago. Put a .52 overdrive gear in a T-5. With 4.10:1 gears, 70 mph in 5th was about 1900 rpm!
Well with a 0.52 ratio,
you would have basically a 2000 RPM drop from 4th to 5th.
SO get your revs up in 4th, get ready to coast and then drop into 5th.
I definitely wouldnt try a WOT shift from 4th to 5th gear.
Only downside is cost. i want to do the same thing, but can't find a good source for cheap O/D gears...unless you've found one.
I beleive astro performance sells them for $200
you would have basically a 2000 RPM drop from 4th to 5th.
SO get your revs up in 4th, get ready to coast and then drop into 5th.
I definitely wouldnt try a WOT shift from 4th to 5th gear.
Only downside is cost. i want to do the same thing, but can't find a good source for cheap O/D gears...unless you've found one.
I beleive astro performance sells them for $200
Well with a 0.52 ratio,
you would have basically a 2000 RPM drop from 4th to 5th.
SO get your revs up in 4th, get ready to coast and then drop into 5th.
I definitely wouldnt try a WOT shift from 4th to 5th gear.
Only downside is cost. i want to do the same thing, but can't find a good source for cheap O/D gears...unless you've found one.
I beleive astro performance sells them for $200
+1
Speed shifting from 4th to 5th is a terrible idea anyway. 5th in a T5 is NOT designed to be an acceleration gear.
When I had my Astro T5 built I had the option of a taller OD gear, but I was a broke college kid at the time, so I opted to save my money. I regret it now, and its probably something I'll do in the future.
I imagine that after you get the hang of driving it with the rev drop it won't seem that severe at all.
LRSjmac
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I've gone from the stock .68 OD to the T5 Z spec OD of .63. Assuming stock tire height with 4.10 gears it's worth a 200rpm drop @ 70mph.
I think a 4.10 car with the taller 1st and 5th gears would be sweet. My beef with ultra-short rear end gears is that it makes the stock 1st gear (3.35 ratio) useless. With a 2.95 first and a .63 or better 5th, 4.10s would probably be pretty sweet.
Either way, I think a 6 speed would be the sickness.
Either way, I think a 6 speed would be the sickness.
If you get the right one.
The gearing in the 6-spd Mustang is like the 5-spd. 6th gear in the Cobra is actually the same as 5th in the GT...they just stuck the extra gear in between 4th and 5th on the GT.
The viper trannys are nice, but you really need to have the HP to turn the steeper 1st and 2nd gears
Someday i'd like to do something like this with a 6 speed...i'd like it set up so that the first 5 gears are typical gearing and then 6th is like double overdrive so i can run 4.10s and have my fun but then drop way down in 6th for highway mileage. Most people think this is a given with the T56 but most of them are geared so that they're basically the same round about gearing in the final gear as a 5 speed, except they more or less have a 6th gear slipped between 4th and 5th. In my buddy's T56, 6th gear is just a teeny bit more overdrive than 5th is in my 3550.
A gear that is going to run you down in the 1000 to 1500rpm range at cruise speed will actually make your car worse on gas. You want something that will sit you 1500 to 1800rpm to get the best fuel mileage. I'd imagine that the T56 from the viper would need some power to actually need it because it is geared at a 500tq V10. Would the ones out of the C5 vette or late model F-Body be a ok choice for a mild street beater setup?
Are you sure? I honestly don't know if there's a significant difference, but I've done extensive testing in my C5, and it gets the best gas mileage right above idle (45-55 mph in 6th gear, which is from just less than 1000 to 1200rpm). Not sure why the mustang would be different.
I don't think that the boxes will work in a mustang without some other modifications, but the case from a Cobra will. The only problem with those is that they do not have the .5 6th gear ratio of the vettes.
Not a manual tranny but in my old 86 chevy silverado with a 700R4 tranny I got better gas milage with 3.73's than I did with the stock 2.73's, I think it was because with the 2.73's it would kind of bog down the interstate, wasting gas, with the 3.73's it stayed at a steady rpm which gets better milage i think.
It's going to depend on each individual car's torque curve, and aerodynamics what the best RPM range would be.
I could see that. I know that in the area I live in with the hills and such that the roads go over my C5 did not like 6th gear under 65mph and would more times than not return worse mileage than 5th. A gas engine, any gas engine while under load has a certain range in which it is most efficiant. My 94 LT1 M6 Formula on the other hand with it's super low end tq loved 6th at about 55mph on up. Like said above though every car is different.
I plan to add a T56 to my fox someday.
If you were to purchase a TKO new you can option the 5th gear ratio to be either .82 or .64 and there is not much cost difference if any, depending on the supplier. Most people opt for the .82 overdrive as there is no huge drop off in rpm when banging thru the gears. At least that is my experience when installing the transmissions. Most of my customers are interested in either road racing or serious street performance and are not looking for or worried about Highway fuel economy.
Yep, that's about what mine does at that 1500-1700 RPM range. I know that 2000rpm is an exaggeration though because that's going over 90mph! I averaged 38.8 mpg on a ~600 mile trip from FL to mom's place in OH. For the first half, I averaged around 36mpg, and for the second half I averaged better than 40mpg. This was not pulled from the driver's information center, but mathematically calculated based on the odometer and fuel measured by the gas station fuel pumps.
At a constant speed of 45 in 6th doing better than 40mpg isn't hard. No A/C, just running the fan to vent air in, and letting it drift in neutral down hills that are steep enough to maintain speed allowed me to average over 40 despite having to drive extensively through the hills of KY into OH. On a flat road it would do better. I'm not talking out of my ass here, and would bet you cash that I could pull the same from any other C5 as mine is just a bone stock '97.
Chris
Well if you really wanna get into what makes good mileage....get a vacuum gauge and hook it up to your car and have it in the interior where you can read it. You'll want your overdrive geared to where the engine is making max vacuum at cruise speeds...which has a bunch of variables like tire height and rear end gearing etc.
Correct. Vac gauges are what those little fuel economy computers go by. When your engine is under load, vacuum drops and so does economy.
So a vac gauge and driving by it can help out a lot
So a vac gauge and driving by it can help out a lot
