Looking for transmission spec (1991 hiace truck 4x4)

Hello all - I am new to the forum. Recently I imported (into US) a 1991 Hiace truck. I am curious about changing the final drive gear ratios but first want to find the gear ratios of each speed within the transmission.

Does anybody have a comprehensive collection of transmission specs, or know where to look? I have done plenty of looking online but cant find them.

Transmission code: R351F
Final Drive: G152
Chassis: U-LH85-MDP
Engine: 2L

Apologies if this is a common question - I wasn't able to find the answer by searching.

I wrote this kind of stuff (about final gear ratios) down in this topic:
https://hiace-super-custom.forumotion.com/t2911-toyota-hi-ace-axle-information

Please also check out the PDF which gives all possible gear ratios.

If you want to have longer gears, so a lower final gear ratio number, you will be able to find it. If you want a higher number for even shorter gears, it will be hard to find.

As you probably know you should change the final gear ratio in both axles.

Since your from the US, you could find a 4runner wrecker fromt the same era (early nineties) and take a lower final gear ratio (longer gears) from there (by also checking the vin plate). But you would have to double check in the parts system (toyodiy.com) to make sure, before you buy something.

The gear ratios of the the R351F are not on the wiki page, but I guess the other R transmissions will not be far off with ratios, so you got an idea.
https://en.wikipedia.org/wiki/Toyota_R_transmission#R350

Thanks for the info - thats helpful. I would still like to figure out the transmission ratios. After looking at what is listed for the other "r" family transmissions, its probably safe to assume 5th gear is 0.8xx.

What is your goal? Do you think it revs too much (too noisey) in fifth gear?
As said, you can choose longer gears, but you may end up with an underpowered vehicle. Of course, diesels have a lot of torque in the low rpm, but still on the highway you shouldn't be too low in rpm.

Yes - Id like to reduce the engine rpm at highway cruising speeds. My current final drive ratio is 5.125, which seems excessively torque-y.

You are right, I will need to be careful not to make too drastic of a change. 4.56 final drive parts are readily available and seem like they could be suitable. I should look to see what other ratios were used by hiaces (with 2.4L engines).

We put some sound isolation in the front cabin, and where the metal goes down into the floor, so also where the round plate above the gearbox is. This really helps. It won't become super silent or anything, but it makes a long journey much more tolerable. We used a mat that is heavy and out of one piece (which you cut into shape) so there are no openings.

The 5.125 final gear ratio is really nice for off-roading. I think most Hiaces have 4.875 which is also quite close.

Hiace4wd wrote:

We put some sound isolation in the front cabin, and where the metal goes down into the floor, so also where the round plate above the gearbox is. This really helps. It won't become super silent or anything, but it makes a long journey much more tolerable. We used a mat that is heavy and out of one piece (which you cut into shape) so there are no openings.

The 5.125 final gear ratio is really nice for off-roading. I think most Hiaces have 4.875 which is also quite close.

Hiace4wd,

Do you have a reference for determining how many splines are on the axle shafts of hiaces?

I may just remove one this weekend.

In the parts system it says this as options:

41201-29735 FINAL GEAR RATIO=41:8=5.125 1 € 915.68
41201-29816 FINAL GEAR RATIO=39:8=4.875

I think the 39:8 or 41:8 indicate the teeth / splines.

I was referring to the splines on he axle shafts, not the teeth of the ring and pinion gears. Sorry I could have been more specific.

Rear is 31 splines for Toyota G axles. Front is 27 spline I thought, but I'm unsure.

I'm considering using diffs from a 4Runner (like you originally suggested). From what I can tell they are 30 spline rear, unfortunately. I am not sure if you can interchange the splined component.

Hiace4wd wrote:

We put some sound isolation in the front cabin, and where the metal goes down into the floor, so also where the round plate above the gearbox is. This really helps. It won't become super silent or anything, but it makes a long journey much more tolerable. We used a mat that is heavy and out of one piece (which you cut into shape) so there are no openings.

The 5.125 final gear ratio is really nice for off-roading. I think most Hiaces have 4.875 which is also quite close.

I don't mean to highjack but you offer such great advice across the forums that I thought I'd try here.

Im looking at 235/245 on my Hiace after a lift kit and adding a swinging door hinge.

Am I looking at super sluggish driving or worse at 245 in the 3.0L automatic super custom?

Do you mean 235 or 245 tyres? Then you will need to give total size. Of which I think they will not fit. Without modifications.

Hiace4wd wrote:

Do you mean 235 or 245 tyres? Then you will need to give total size. Of which I think they will not fit. Without modifications.

Sorry for the lack of info.

1995 Super Custom. 2" lift kit. Swapping to these wheels: https://www.motegiracing.com/product/wheels/mr150-trailite/?attribute_pa_finish=matte-bronze

Considering either 235/75/16 or 245/75/16 with an offset of 0

Door clearance is not an issue due to an imported, modified hinge.

Just wondering now about gearing and driving experience, not concerned about fitment as I'm prepared to do some body work.

Thanks in advance!