Gear Ratios

[dougie]

Don't forget that like a new engine, your new differential gears need break-in as well. Here's some guidelines: https://www.marlincrawler.com/tech/diff/differential-break-and-care-information I agree with Michael, you don't really need, nor want, anything different than GL4 in the rear. Your speedo will now be out of calibration. You can either send it off to a place like Nisonger or use this GPS based device I use: https://www.classicautoinnovations.com/classic

Or you could have your gears REM treated before installation, https://weddleindustries.com/services/house-rem-polishing-process-weddle-industries
I have all my race gears REM finished prior to install.

 

[RAC68]

Hi All,

Although I have been considering the 3.54 gear set for decades, it was one modification that I never saw that much need to do. Yes, cruising on highways would be a lot more pleasant when keeping up with today's normal cruising speeds of 70+++ and higher. However, although I do have a great deal of confidence in my Healey, I have found high speed highway cruising is not something I would prefer taking to do.

With the 3.9 rear, keeping up with today's highway traffic usually means I will be pushing RPMs to the 4K range and higher. Additionally, it is quite demoralizing being so casually passed by a small low powered econo-sedan zipping along. Yes, a 3.54 would help the situation but I probably would still not enjoy highway driving in my Healey. I guess I can put up with the discomfort for the infrequent times I drive on a highway and see it as a stimulant for continuing to drive on back roads at lower speeds where I can take time to see the scenery. Yes, the Healey could have been built to better handle today's world but it maintains its character with its strange operational quirks and difficulties and was great when I was 24 and brings me back each time I drive.

Just my thoughts,
Ray(64BJ8P1)

 

[pan]

Bob, your maths are the same as mine. I have a 3.667:1 ratio in my '54 BN1 (spiral bevel, four stud axle) and I calculated that the difference from the standard 4.125:1 ratio is 11%. With the low down torque of the four cylinder engine I have found starting in "1st" (2nd in the A90 gearbox) still adequate. But like most BN1s my selectors have been modified to allow selecting "bottom" (1st in the A90) so a start on a steep hill does not present a problem.

 

[steveg]

Don't forget that like a new engine, your new differential gears need break-in as well. Here's some guidelines: https://www.marlincrawler.com/tech/diff/differential-break-and-care-information I agree with Michael, you don't really need, nor want, anything different than GL4 in the rear. Your speedo will now be out of calibration. You can either send it off to a place like Nisonger or use this GPS based device I use: https://www.classicautoinnovations.com/classic

Rick - did you mount it under the dash?

 

[HealeyRick]

Rick - did you mount it under the dash?

I tried that, but it makes too much noise mounted in the interior. You could mount it in the engine compartment, although it's pretty noticeable if you are trying to maintain an original appearance. I mounted it on the chassis rail next to the transmission. It's not waterproof so I sealed all the edges, don't drive in the rain often, and so far it's been fine after 2 years.

 

[HealeyRick]

Or you could have your gears REM treated before installation, https://weddleindustries.com/services/house-rem-polishing-process-weddle-industries
I have all my race gears REM finished prior to install.

Interesting process, Dougie. Always something to learn from your posts. Did you do it for performance gain, durability, or both? Do you do your transmission gears as well?

 

[gonzo]

Even SoCal's "minor" parkways are three to four lanes posted for 55+MPS, so there's just no good way to avoid high(er) speeds. Healey needs longer legs to cope and not become a hazard to navigation!

I'll look into the associated cost to micro-polish / treat the gears, but appreciate and understand the benefits of the process. I like the GPS tech add-on too; some aftermarket gauges have GPS internals and operate similarly.

To review: GL5 for rear differential and GL4 (like redline's MT 90) for transmission. Thanks, GONZO

 

[Michael Oritt]

After installing the 3.5 Lempert gear set I had a converter box made by a local speedometer shop that did not involve sending the speedometer head out--the guy simply made up a shorter drive cable which goes into the box with another cable coming out of the converter to the speedo head. It ran about $150.00 and is dead-nuts on.

If you don't want to go to the time and expense of having either a converter box or a converted speedo why not simply use any one of several phone routing apps that give you accurate speed and will even generate an audible warning if wanted. I use WAZE and think it is wonderful--in addition to accurate routes it tells me my speed and the presence of speed/red light cams ahead plus traffic jams, etc. etc.

And yes--GL4 in any transmission containing brass synchros and GL5 in the differential which has no yellow metal. FWIW the Toyota box is very strong and fast and you could probably get by with any GL4 tranny oil but in the MG transmissions of my Elvas the MT90 produced a definite improvement in shift speed,smoothness, etc. over SAE 30 engine oils and I believe that most folks with original Healey transmission who have switched up to Redline MTL or MT90 will agree.

 

[HealeyRick]

I like the GPS tech add-on too; some aftermarket gauges have GPS internals and operate similarly.

GONZO

The nice thing about the Classic Speed or a converter box is you get to keep your own instruments. The aftermarket GPS speedos are pretty neat, but they don't look original. You can get the Speedhut gauges with some custom work that I've seen the Sprite guys with, but they don't offer a speedo that will match the gauge color for those of us running the ivory stock gauges. Speedo shops in my area are nil, so the option of a converter box was out for me. Even though I have a V8 in my car, I strove to keep the car as original as possible, including all the gauges. It was a bit of a struggle making Ford and Smiths play together nicely, but I think it was worth the effort as all the stock gauges now successfully monitor the Ford's vitals:

 

[gonzo]

Looking good HealeyRick! I too like rockin' the Healey's ivory / gold faced gauges and strive to keep things looking original.

 

[HealeyRick]

Looking good HealeyRick! I too like rockin' the Healey's ivory / gold faced gauges and strive to keep things looking original.

Thanks. If all you are doing is changing rear gears, the simplest thing to do and probably the least expensive is ship it off to Nisongers after giving them a call and the rear end has been installed. They will give you directions on how to measure the distance your car travels in one revolution of the rear tire and send it to them so they can recalibrate your stock gauge and use your stock speedo cable. Because I am using a Ford transmission, I had to get a bit more involved.

 

[vette]

I got a GPS fix too. Real easy, convenient and cheap.

 

[steveg]

I had Nisonger do mine once; ditto West Valley Instruments. Both were fine. Nisonger built me a Toyota-to-Healey speedo cable.

I've settled on the 180 x 15 Michelins with 3.54 diff -- so for me the simplest solution was to have the speedo recalibrated to that combo. End of story.

PS - I've heard the little in-cable ratio-changing gearboxes are unreliable.

 

[Deleted member 21878]

i changed the rear gear in my TD a few years back. i had Nisonger re-calibrate the gauge. if i remember correctly you take out the speedo. mark one side of the square cable end. then push the car... 59'2-1/2"???? do it a few times and get an average of the number of times the marked endge goes by. say 15 and 3/4 or something. from there they make it work. mine came out perfect to my GPS unit.

not terribly expensive either as i recall. they also went thru my gauge and stopped the bouncing at the same time.

 

[steveg]

52 ft 9-1/2 inches (1/100 of a mile).

You can put a piece of tape on the speedo cable and rig up a pointer on the bumper to point to marks on the street. Then push the car through the distance a few times and send them the average. Nisonger told me to the nearest 1/4 turn is good enough.

 

[Michael Oritt]

Steve--

I have had the inline converter installed for probably 35-40K miles without a problem.

 

[RAC68]

Hi All,
Just came back from a drive in a BJ8 with the 3.54 rear and I definitely see the cruising benefits of giving the Healey longer legs. After reading the many comments, it seems there are 2 major issues (1. Access/Cost, 2. Speedometer Correction) to address when making a change decision.

It seems that the 3.54 R&P has become a scarce commodity and, as such, demands a very formidable price. As I was told, the 3.54 gear ratio was chosen because it already existed in some Healeys and, therefore was longer and available for Healey's rear setup.

Is 3.54 the optimum rear ratio for a O/D Healey? Would it be practical to modify an R&P from another car to fit the Healey? Since scarcity has caused prices for the 3.54 to become ridiculously high, how would the acquisition and modification costs of another gear set compare?

Although I do see the benefits of the 3.54, the owner felt he would have preferred a 3.09 (as in the E) with 5-speed for highway cruising down the NJ Shore and felt the Healey's 6 could easily handle it. Although this is not my preferred use for my Healey, his modifications would make a Massachusetts trip much more comfortable

Any Thoughts?
Ray(64BJ8P1)

 

[dougie]

Interesting process, Dougie. Always something to learn from your posts. Did you do it for performance gain, durability, or both? Do you do your transmission gears as well?

Yes on all three.

 

[vette]

Hi Ray, I was always a little disappointed in the results of my 3:54 gear change in that it didn't drop the rpms enough for my satisfaction. But there is no denying it is a help, obviously. I have 165 tires and my rpms run between 2700 & 2800 rpms in OD with the 3:54 gears at 65 mph. I was hoping that it would be more like 2500 rpms. As a reference my '70 Vette runs about 2500 rpms at 65 mph with 3:08 rear gears and similar diameter tires. I verify the speed in both cars with a gps unit so speedo calibration is not a factor in these figures. If I could get 3:08 gears for the Healey I would do it because I believe the torgue of the engine is satisfactory for street use.

 

[Bob_Spidell]

Of course, another option is going with a taller OD (28%). At least one (fairly) well-known Healey aficionado maintains that makes the best highway cruiser of all. Not mentioned yet is that the 3.54 diff makes second gear more usable and first usable in more situations.