High RPMs on the freeway with manual transmission mini trucks

[MISWFL]

Is what some people actually like?

I don't understand that at all, especially with a 5 speed transmission. My definition of high RPMs is basically anything over 3000 RPMs going with or close to the flow of traffic. Of course the flow of traffic has risen a lot since the 1970s 55 MPH was lifted.

My first few cars in the late '80s were air cooled VWs with tiny engines and 4 speed manuals. Adequate for 60ish mph. Long uphill grades required dropped down to 45 in 3rd.

My first modern car was a '78 Rabbit Diesel with a tired 1.5 and a 4 speed manual. Very similar to the air cooled VW, but a bit more power and far better fuel mileage. I sold it to buy a real car. A 1983 VW Rabbit GTI. Almost 100 hp and a 5 speed close ratio manual transmission. Very fast and fun, but highly annoying on the freeway. It would spin around 3700 RPMs on the freeway going 60ish. Just barely touch the gas and it would jump up to 75-80 almost effortlessly. Max speed was like 105 at redline. It could even pull that up grades driving to Lake Tahoe.

I was reading all the magazines at the time and learned about gearing. I put a junkyard 5 speed from a Rabbit Diesel into my GTI. Such an improvement going from a .85 or .80 ratio 5th to a .71 ratio 5th gear. I don't remember the difference in the final drive ratios. It cruised so effortlessly. I ended up learning how to repair the missing differential snap rings without taking the transmission apart and to add the .71 5th gear to it. That was a nice combination. 1-4 close ratios and a very tall 5th gear.

The reason I'm mentioning this is because my '78 Datsun 620 with a 5 speed is the same way as my GTI was before the transmission swap. Very low gearing so not comfortable on the freeway at all. Apparently it's got an early 5 speed and I need to look for a later one to get taller gearing, or maybe a 5th gear only swap. I brought that up on a similar Datsun forum and everyone said that high RPMs on the freeway is just what you want for a mini truck. Just drive slower if need be. Seems strange to me, especially when I told them that I wasn't towing or carrying any loads. I don't like sharing the slow lane with the semi's because my vehicle is "tached out" going 60 in a 70 zone. I don't want the same thing happening with my 1990 XLT 2.9 4x4 auto that I'll eventually swap to a 5 speed. I want to be able to effortlessly keep up with traffic and not be close to being "tached out". If I'm towing or carrying a load, I don't mind parking in the slow lane then.

 

[Curious Hound]

Depends on the engine. Most 4cylinder engines, have less torque, so they need to be run at higher rpm to get build the necessary horsepower. The 4.0l and 2.9l have better low end torque. So they operate OK at lower rpms. The 3.0l Vulcan is designed with poor low end torque. Its torque and hp peaks are at higher rpm. So, it operates best over 3,000rpm, closer to 3500. If I drive it that way, the thing is a great engine. So, look at the design characteristics of the engine. Then gear it and drive it to use those characteristics to your best advantage.

 

[Roert42]

2nd that. For sure how tall of gearing is needed is related to where the power band is and where you are driving it.



That said, I rarely drive in the turnpike so I’m not normally going above 55/60mph.

With the m5odr1-hd and 3.55s behind my 4.0sohc, I am very happy with the gearing. 2-3 is a little wider then I would like, but not bad. 5th is short enough I can use it above 45 and not dog the engine, but still has room. I don’t hit 3k rpm until about 70mph.

If I was making my own engine from scratch I would probably make 3rd a little shorter so it was more of an even spread between 2-4. Then add a 6th so I could Cruze at 2k rpm at 65.

If I was doing a lot of interstate driving I might even put taller gears in the rear to give it better cruising ratio.

 

[JoshT]

Sounds to me like things just happened to work out with the GTI. I would guess that the GTI probably also had a very forgiving powerband allowing you do get those results.

For the Datsun and Ranger both, I think you might be better served by adjusting axle ratio. Potentially easier and more bang for the buck.

On the older, pre OD, vehicles, it was a pretty common occourance to adjust gear ratios and/or tire sizes to achieve much the same results as what adding an overdrive accomplished. No reason that the same won't work for a vehicle with OD.

If it'll let me attach it and you can use Excel (or equivalent), here's a handy little spread sheet I found a few years ago. It will let you compare a lot of gear ratio, engine speed, vehicle speed and other info. Use it to compare best options for acheiving your desired outcome. Didn't let me attach as an excel doc, but did as a zip file.

 

[scotts90ranger]

There's a lot of factors... on my '97 Ranger with 2.3L it's kinda gutless so it likes the R's and it drives great with the gears and tires sized to get 3000rpm at around 70mph in 5th gear which in my area covers the expected speeds perfectly... My V8 Explorers on the other hand prefer to be at 2000rpm at 70mph for mileage, even going to 2200rpm takes a ~1.5mpg tax...

 

[superj]

4.10 rear end is great for the 3.0 v6 in my old 04 ranger and 5 speed. Maybe you should look for a 4.10 rear end to swap in?


My 71 karmann ghia would do 100 really easily with a single port 1600 and pic 3 carb tuned for the short stinger exhaust and the 010 distributor.

 

[bobbywalter]

with a 2.9 and stock tire size...going 100 mph wont be an issue.


a4ld od ratio .75


m5odr1 ratio .79

 

[lil_Blue_Ford]

One thing that greatly helped my 92 4.0 Ranger with 3.73 gears and an A4LD trans was to do a shift kit, valve body work, and adjusting the bands. Really woke the truck up and it did way better all around. Highly recommend.

 

[bobbywalter]

4.10 rear end is great for the 3.0 v6 in my old 04 ranger and 5 speed. Maybe you should look for a 4.10 rear end to swap in?


My 71 karmann ghia would do 100 really easily with a single port 1600 and pic 3 carb tuned for the short stinger exhaust and the 010 distributor.

the 2.9 is a revver compared to the 4.0.... but 410 is way too far for anything under a 31 tire. perfect for a 3.0 though.

 

[JoshT]

the 2.9 is a revver compared to the 4.0.... but 410 is way too far for anything under a 31 tire. perfect for a 3.0 though.

What if the goal is spinning tires instead of cruising speeds?

 

[bobbywalter]

What if the goal is spinning tires instead of cruising speeds?

308 gears for frying tires

 

[bobbywalter]

and a hemi

 

[85_Ranger4x4]

What if the goal is spinning tires instead of cruising speeds?

With a 2.9?

 

[JoshT]

308 gears for frying tires

Really? I would have expected the opposite, or is that when used in conjunction with the next post?

FWIW, I'm thinking about tires several inches shorter than a 31. More like stock 1st gen 2wd size. I know, a little off topic.

With a 2.9?

Of course not.

I was thinking about a 2.8L, to be replaced by a 2.3L or 4.0L when I finally finish it off. All of which I have it will have. None of them for a street driven vehicle, at least not in a commuter vehicle capacity.

 

[bobbywalter]

Really? I would have expected the opposite, or is that when used in conjunction with the next post?

FWIW, I'm thinking about tires several inches shorter than a 31. More like stock 1st gen 2wd size. I know, a little off topic.



Of course not.

I was thinking about a 2.8L, to be replaced by a 2.3L or 4.0L when I finally finish it off. All of which I have it will have. None of them for a street driven vehicle, at least not in a commuter vehicle capacity.

short gears. short speed. and yes easier to break initial traction.

but we are talking about engines that are nutless cowards...even a stock windsor is a joke.

so you have to line lock or brake torque if smokin tires is the goal.

and if spinning tires is the goal and using that fashion to get them burning....the high gears spins the balls and smoke out of them with the least amount of speed on the engine. 2nd gear held manual wot 308 gear spin is waaaaaaay more impressive than a 456 gear spin.....


now donuts....thats a different deal.