Gearing on my 60

[nwfj62]

I’ve got an HJ81 swap, G Turbo, H55 and 370 gearing. My issue is at 60 im pushing 3000 RPM’s. I’ve been told that this is just the nature of the beast. Looking for any input. Thanks.

 

[Mace]

You sure you have 3.70's? on 31" tires you can do about 80 at 3k with the H55F overdrive.

4Lo.com :: Final Gear Ratio, Crawl Ratio, Tire Size Calculators

 

[nwfj62]

Hmmm, my thoughts exactly and time to pull the cover.

 

[Seth S]

With stock axles on my 2F powered 60 and the 4 speed I was doing 65 at 3000 rpm on stock sized tires in 4th gear (based on stock tach needle).

 

[nwfj62]

Ok confirmed 380 gears. 60 mph and using my factory tack I’m at 2900 in 5th gear. 33x10.50x15 BFG’s.

 

[Mace]

How did you confirm that?

 

[efjay6tee]

Something isn't right...either your tach is off or your gearing assumption is wrong. The H55f has a 5th gear of .845 and your tire height is 33". These are the known facts. The unknown is the gearing at this point. I wasn't aware that you could get a 3.8 ring/pinion, but if that is possible your RPM's would be 1945 at 60mph.

If your RPM is, in fact, accurate, that would mean your gearing is closer to 5.8 (and I don't know if that's possible either).

Use this link to calculate RPM - Engine RPM Calculator

 

[nwfj62]

Well I’m only confirming on the invoice from the guys that installed. Doesn’t make sense, “they” claims do to the diesel/manual combo that it’s the nature of the beast. Not agreeing with that theroy. Cover off is the only real way to determine what’s inside. Thanks for all the input. Thoughts on what’s the proper gearing? 410’s ? Looking for highway cruising.

 

[mwebfj60]

You can put a mark on the driveshaft and a mark on the tire, count the revolutions of each and compare the ratio...if you are precise with it, that will give you the R&P gear ratio.

 

[efjay6tee]

I’ve got a 1hdt/h55 combo with 34s/3.70 and I can cruise at 65 mph - 2k rpm and I love it.

 

[cruisermatt]

What transmission do you have?
I see several assumptions you have an H55f.

 

[cruisermatt]

And where is your tach getting it’s signal? Was this originally a U.S. FJ62 or FJ60? (Username and thread title conflict)

 

[Mace]

I’ve got an HJ81 swap, G Turbo, H55 and 370 gearing.

Not much of an assumption.

 

[nwfj62]

I have an H55 trans. The engine is from overseas out of a 95 LC. I can’t rule out the tach as they did use a tach coverter and that could be the culprit. I’ll have to dig and see where the signal is coming from.

 

[Mace]

Does it sound like it's hitting 3K? That motor redlines at like 3600 or 4K right?

I'd find a way to check and see if the tach is reading properly. I doubt it is.

 

[efjay6tee]

I was going to say the same thing @Mace. If mine hits 3000k on the highway I’m going damn near 90 and feels like I’m about to go plaid.

 

[Mace]

Points for Spaceballs...

 

[nwfj62]

Going to look into the tach converter and or just replace it entirely. Power to burn at 3k with the new G Turbo so I’m leaning towards that.

 

[cruisermatt]

Not much of an assumption.

My bad missed that part.
And yes it sounds like the tach is wrong.

 

[Landpimp]

Those are the close to the same numbers I get with my fj60, 33x10.5 , 4.10gears and just a 4 speed, so yes something must be off.

Ok confirmed 380 gears. 60 mph and using my factory tack I’m at 2900 in 5th gear. 33x10.50x15 BFG’s.