Diff gears 35”

[nielsc]

I have a 1HDFT hdj80 wich has been converted to the electronic a442f automatic transmission, but still has the stock manual 3.73 gears. Since Im running 35s the gearing is way out because the automatic is supposed to have 4.1 diffs.
Im considering swapping in a set of 4.1 diffs, or change my ratio’s to 4.56.
Anyone on here with a diesel auto (4.1) running 35s ? How does it drive? How much RPM at 60mph/100kmh ? Do you feel 4.56 would be better ?
Thanks

 

[Chris]

I'm running a set of 35" BFG ATs which came off an auto. That ran stock diffs and when I bought them I asked just how had it driven? All I can tell you is that they said it it was fine. They barely noticed a difference. I'm not sure on here who is running larger rubber in an auto with std diffs. Gary820 has bigger rings on his petrol 80 and is running std diffs. And that thing is awesome.

Having had 37's and 4.56 diffs, I really don't think you need to go more than 4.1 if you change them.

 

[Gav missin]

I'm running a set of 35" BFG ATs which came off an auto. That ran stock diffs and when I bought them I asked just how had it driven? All I can tell you is that they said it it was fine. They barely noticed a difference. I'm not sure on here who is running larger rubber in an auto with std diffs. Gary820 has bigger rings on his petrol 80 and is running std diffs. And that thing is awesome.

Having had 37's and 4.56 diffs, I really don't think you need to go more than 4.1 if you change them.

I'm running bfg 35s on standard auto and never noticed any difference on K plate 80 and 35s maxis muds on J plate auto offroader. Tow with the K plate a lot also. Never considered it any issue.

 

[Chris]

There you go

 

[nielsc]

Thanks for the good input. What RPM do you folks sit at at 60mph? This way I have an idea at what it will be like.

 

[Gav missin]

Thanks for the good input. What RPM do you folks sit at at 60mph? This way I have an idea at what it will be like.

Roughly 2000 rpm is 60mph.

 

[Gary820]

35s on my auto petrol, no big difference with them on tbh. They're more noticeable on long steep inclines (it's what kick down is for) 60mph is below 2k rpm

 

[clivehorridge]

Blimey, on 33s I’m at 2500 doing 60 mph

 

[nielsc]

I switched to stock wheels and tyres and now it does +-1950 RPM at 60mph, I forgot about how good it drives with the stock wheels, so much power available and shift points are much better. 4.56 would bring it back to stock but I think 4.1 will be a better compromise when doing highway speeds.
Seeing the response and doing some maths it looks like this will be more or less the same as 4.1s on 35s, and looks the way to go.
Also the easiest and cheapest as 4.1 gearsets or diffs are more common to find at the breakers, and 4.56 are only available new and upgraded strength.

 

[Grimbo]

285/75/16 BFG At's on my 24V Manual = 60mph true (by Sat Nav) at 2100 rpm

 

[Alexandertheallright]

K plate 80 auto diesel running on 35” cooper stt pro on 15” rims running 2000 rpm at 60, with 17 mpg, standard everything and all is fine

 

[BatWatson]

I have a 1HDFT hdj80 wich has been converted to the electronic a442f automatic transmission, but still has the stock manual 3.73 gears. Since Im running 35s the gearing is way out because the automatic is supposed to have 4.1 diffs.
Im considering swapping in a set of 4.1 diffs, or change my ratio’s to 4.56.
Anyone on here with a diesel auto (4.1) running 35s ? How does it drive? How much RPM at 60mph/100kmh ? Do you feel 4.56 would be better ?
Thanks

I don't know from personal experience but a number of people at IH8MUD talk about diffs with a ratio of 4.88 when going above 33s on the HDJ80s.

 

[Chris]

I ran 37's on 4.56 on an auto. 4.88 is not necessary really. But of course it depends if you are starting from an auto or a manual.

 

[nielsc]

I don't know from personal experience but a number of people at IH8MUD talk about diffs with a ratio of 4.88 when going above 33s on the HDJ80s.

I think this concerns the petrol 80s

 

[nielsc]

Anyone knows what quality is like with this Milner off road gear set ?

https://www.milneroffroad.com/toyot...ial-rebuild-kit-front-final-gear-4110-ratio-1

It's not really expensive considering everything is in the kit, but I am more concerned about the quality of the ring and pinion?

 

[Chris]

I've built two of those - or it might be three. Very good. Perfect pattern, owners very pleased with their new quiet diffs. Just watch the pinion seal though. Not genuine and guess what? One is leaking already. You can swap them on the car but what a pain.

 

[nielsc]

As long as the bearings are OEM Koyo and the gearset is as strong as the original all is fine, I'd order a genuine seal anyway. But if the bearings aren't OEM I think i'll pass.

 

[Chris]

They are genuine. I've fitted many sets of those over a number of years. I bought a Roughtrax set recently and they were identical to the Milner ones.

 

[nielsc]

Good thing they are Koyo bearings. Any toughts on ring and pinion strenght? I run 35s and it really gets used now and then ... I really don't want to do all the work and then snap a few teeth after a while

 

[Chris]

I'm not sure how I could possibly answer that nielsc. None of the sets I have fitted have broken. I can't say any more than that really. You could always get a set from Toyota. Or perhaps a second hand set and take a chance that they're not going to be noisy. I run 35's too and if I needed a new R&P, I'd probably buy these. I had a set of nitro ones from Just Diffs in the States and I broke a tooth backing out of the driveway.