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how much power can the gearbox take

General Tech Talk

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Posts: 1908
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how much power can the gearbox take

Post by known 2 »

wonder how many hp or torque can a 75 series 5spd take before it constantly breaks? as i have a 308 in the car and want to do it up to around the 400hp mark.

cheers
kaylee 2004 hdj78 RV. 33 mickey atz's, winchbar, 3i lift, 3i exhoust, spoties, roofracks and ufh. pimped interior .

86 lwb zook wt soa, 33's, locked, bard up, prety lights. monster tacho:/
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Post by V8 Middy »

I had the head flowed and a lumpy cam put in, approx 120kW at the rear wheels on 35in tyres. 0-100km around 8sec or so if that gives you more of an idea.

I haven't broken anything yet although my understanding is that 5th is the weak link in that box and with the 35's I'm spendng a lot of time in 4th. Off road I guess a lot comes down to how you drive. I'm sure if I revved the old 3F high enough and dumped the clutch I could have broken something!!!
73 Series Middy Cruiser 308 VN V8 OME 2in Susp lift 2in Body lift 35in Pro Comp X-Terrains
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Post by known 2 »

well once i get crawler gears i spose i will be driving it very gently but noy i rev the shit out of it offroad cos it has no flex.

just want more power so i can get along the road better will be running 33's on street.

the motor has a mild cam and the valve tiiming is changed a bit so it's got more go than a standard 308 black
kaylee 2004 hdj78 RV. 33 mickey atz's, winchbar, 3i lift, 3i exhoust, spoties, roofracks and ufh. pimped interior .

86 lwb zook wt soa, 33's, locked, bard up, prety lights. monster tacho:/
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Post by 4x4Monkey »

as long as ya dont go dumping the clutch at 8000rpm lol
it should hold up for now. But the question is for how long
Dont worrys There's No Sugar

My 4x4 Is too clean.... Needs a Mud Pack
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Re: how much power can the gearbox take

Post by 80UTE »

known 2 wrote:wonder how many hp or torque can a 75 series 5spd take before it constantly breaks? as i have a 308 in the car and want to do it up to around the 400hp mark.

cheers
If your talking 400 HP out of a 308 it will be no good off road as it would have less low down torque than a Camira engine and absoloutly hopeless offroad how much do you think you need to spend to get 400 HP easy 10k+ and if you had 400 hp you would be strugling to keep it on a track. As for the gear box strenght it will handle what ever the 308 will put out, had a mud racer years ago with a 380 small block Chev 498 HP on the dyno ( cost over 20 K ) 10 years ago and had a 75 box/transfer and never had a prob. Have mates in the comp scene with goods 350's and never had a prob and a mate with a 454BB in his everyday 75 and it keeps going no probs. The only box to keep away from is the HZJ75 as the gears and shafts are crap and s**t them selves all the time. Any one from a 60, 70 or 75 with the with the 2F, 3F, 2H, 12HT, 3B or 13BT engine are all good keeping in mind that the 4cyl Diesels have a longer input shaft.

Wally
THERES ONLY ONE SUBSTITUTE FOR CUBES AND THATS MORE and if you want more inchs stroke it !!!!!!!!!!!
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Post by CWBYUP »

Unless you have efi I would not even bother with trying to get 400hp out of a 308. There ticking time bombs.

Take it from someone who has spent big dollars on 253 / 308 carbie engines, its just not worth the coin spent.

Just buy a 400 small block. You can get about 350 to 450 Hp easy with sh*t loads of torque ( which is what you need offroad ) and there reliable.

For what you will need to spend on the 308 you could drop 400 and t 700 auto in and have enough money left to put 38's on it.

Dont get me wrong its just my opinion but i wasted alot of money chasing Hp in 5L.

Nick
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Post by Jimbo »

I dont think he asked how to get the power and what problems the motor will have. Just gear box strength.
GQII Patrol YAY!!
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Post by known 2 »

thats all usefull info thanks. i just wana get a bit more out of it for now cos it's allready there rather than buying another conversion kit.

thinking of maybe putting a stroker kit throo it to get more torque cos i like the 308 drives nicer than a 350 chev
kaylee 2004 hdj78 RV. 33 mickey atz's, winchbar, 3i lift, 3i exhoust, spoties, roofracks and ufh. pimped interior .

86 lwb zook wt soa, 33's, locked, bard up, prety lights. monster tacho:/
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