m&mv80 Posted April 13, 2009 Share Posted April 13, 2009 as the title says really, i have the chance to get a couple of 4.7series diffs and its got me thinking, im running a v8 in my 90 with 35 inch tyres and it could really do with the ratios changing as it struggles a bit pulling away and cant hold 5th on any sort of a hill, having seen the price of 4.1 ashcrofts i was wondering if you can strengthen series diffs as a cheaper alternative, maybe pegging them would help? i have heard people say they are not as strong but by how much? so can i just use the diffs as they are? will pegging help? swap the crown wheel and pinion into my origional housings? (i believe you need a spacer to do this) will my detroit locker fit if i change the ratios? keep saving until ican afford the ashcrofts parts? its only for playing not for competition, im quite sympathetic to the drive train and ive not broken a std 3.54 as yet (touch wood) thanks in advance martin Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted April 13, 2009 Share Posted April 13, 2009 4.7s are stronger than 3.54s, but pegging either makes them much much stronger Nige Quote Link to comment Share on other sites More sharing options...
landmannnn Posted April 13, 2009 Share Posted April 13, 2009 No shortcuts here. Series rover diffs are very weak. ( Cadbury's make them, no coincidence that they are made in the same city) Quote Link to comment Share on other sites More sharing options...
Aragorn Posted April 13, 2009 Share Posted April 13, 2009 I find it hard to believe a V8 is struggling to pull the 90... Even a rover one, i knew they were ropey engines at best, but i'd still have expected it to perform better than a derv! What transfer box ratio are you running? Is the engine actually running properly, or is it half dead? Quote Link to comment Share on other sites More sharing options...
Rich_P Posted April 13, 2009 Share Posted April 13, 2009 I find it hard to believe a V8 is struggling to pull the 90... Even a rover one, i knew they were ropey engines at best, but i'd still have expected it to perform better than a derv! I wouldn't be sure if it could be an early LR unit! I think they only produced just over 100bhp and similar torque to a standard TDi? Quote Link to comment Share on other sites More sharing options...
BogMonster Posted April 13, 2009 Share Posted April 13, 2009 I wouldn't be sure if it could be an early LR unit! I think they only produced just over 100bhp and similar torque to a standard TDi? Correct - 114bhp. The police here used to have one of these (carb 3.5 in a 110) and while it made a lovely noise it was no quicker than a Tdi and just used twice as much fuel ... it wouldn't have coped well with a gearing increase but fortunately was demolished by a falling peat shed and replaced with a 300Tdi. Out of interest what is the weakness in Series diffs i.e. what bit breaks? I have heard plenty of times that they are made of cheese but don't recall lots of people here breaking them in the old days so wondered what went on them? Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted April 14, 2009 Share Posted April 14, 2009 ^^^ They break in much the same ways as others diffs, I have in the past mainly blown the centres (Planet geras) apart, but also the pinion / CW mesh can be forced to move apart - jump and strip a selection of teeth. The 4.7s are just a tad stronger than 3.54s, but still will blow apart quite easily Quote Link to comment Share on other sites More sharing options...
Off Road Toad Posted April 14, 2009 Share Posted April 14, 2009 Standard 4.7's are weaker than 3.54 gear sets. the tooth form is considerably thinner and the pinion head is also smaller. we've just spent over 15K on testing gears and shafts. pegging probably won't save it. If your dead set on using 4.7's then buy some new ones from Bearmach or someone. they shoudn't be that expensive. old ones may suffer from fatigue simply because of age/mileage covered. The 4.75 aftermarket ratio is not to be confused with the series 4.7, it has a completely different tooth form (much larger) though the pinion head is still fairly small. Why don't you fit a 1.6 ratio transfer box? it would be easier. Steve. Quote Link to comment Share on other sites More sharing options...
Jon White Posted April 14, 2009 Share Posted April 14, 2009 Wot he said. HFH is wrong - 4.7's are NOT stronger that 3.54's. I got so sick and tired of breaking them I put KAM 4.75 ring and pins in in the end, and pegged them aswell! I was breaking the teeth off of standard 4.7's with an asthmatic 2.25 petrol in my standard series on 7.50 mud terrains so a V8 90 with 35's will break them before you even get out of the car park! 3.54's are alot stronger by comparison. Jon Quote Link to comment Share on other sites More sharing options...
will_warne Posted April 14, 2009 Share Posted April 14, 2009 Wot he said. HFH is wrong - 4.7's are NOT stronger that 3.54's. I got so sick and tired of breaking them I put KAM 4.75 ring and pins in in the end, and pegged them aswell! I was breaking the teeth off of standard 4.7's with an asthmatic 2.25 petrol in my standard series on 7.50 mud terrains so a V8 90 with 35's will break them before you even get out of the car park! 3.54's are alot stronger by comparison. Jon I concur. I used to strip 4.7s using a very tired 2.25. On my 90 (35" Simex) I never stripped a 3.54 even after I put in the 2.8 tgv and I gave it a fairly hard life. I later had them pegged for piece of mind and they still live on in another 2.8 tgv powered car. Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted April 14, 2009 Share Posted April 14, 2009 I have broken a 4.7 in a S1 with a sh@gged 2ltr petrol! wizzed a tooth of the crownwheel. Quote Link to comment Share on other sites More sharing options...
m&mv80 Posted April 14, 2009 Author Share Posted April 14, 2009 ok to answer a few questions, no there is nothing wrong with the engine its actually quite sweet but its the old factory fitted carb version and they are no where near as powerfull as you might think, as bogmonster said about 114hp, i bought it completely factory standard and with the 205 tyres she was great at taking off from the lights and even with the 7.50s not to bad but having fitted the 35s its just struggling a bit so im sure its the size/ratios thats are the problem, no idea of the transfer box ratio, its whatever a standard 1988 v8 csw was fitted with, i know it has the lt85 gearbox, like i said im not to hard on it but have given it a bit of grief at times and im suprised how well the 3.54s have held up as everyone said they wouldnt last 5 mins with 35s, hence the reason i was wondering how weak the series diffs really are, by the sounds of what you are all saying is that they are not going to be good enough but i would still like to hear if anyone knows different, oh and would i still be able to use my detroit in the rear or will it not fit series diffs? thanks for all you input so far Quote Link to comment Share on other sites More sharing options...
landmannnn Posted April 14, 2009 Share Posted April 14, 2009 no idea of the transfer box ratio, its whatever a standard 1988 v8 csw was fitted with, i know it has the lt85 gearbox, From memory the v8 csw from late 80's was fitted with a 1.19 ratio transfer box. It also sported 135bhp, not much more than 114bhp but still better. Certainly a bit of a tune up might help. If not enough then a 1.4 transfer box would be easy to find, certainly easier (and cheaper) than changing diffs. It should be running 4 pin diffs / 24 spline halfshafts already which might explain why they are still ok. Quote Link to comment Share on other sites More sharing options...
widget Posted April 14, 2009 Share Posted April 14, 2009 From memory the v8 csw from late 80's was fitted with a 1.19 ratio transfer box. It also sported 135bhp, not much more than 114bhp but still better.Certainly a bit of a tune up might help. If not enough then a 1.4 transfer box would be easy to find, certainly easier (and cheaper) than changing diffs. It should be running 4 pin diffs / 24 spline halfshafts already which might explain why they are still ok. Spot on - on both counts. I had a 1988 90 V8 CSW and swapped the transfer ratio from 1.2 to 1.4 when fitting 235/85x16s. The constant swapping between 5th and 4th on the motorway was painful. (btw The modest power increase co-incided with the change from Strombergs to SU carbs.) A 1.4 ratio transfer box with 35" tyres slightly ups the gearing over stock - but should be OK. If you like a responsive 5th gear performance then a 1.6 is your best bet. I bet the cam's flat as a pancake too. It will have a 4 pin in the back if original - well worth hanging onto and the stronger half-shafts. Quote Link to comment Share on other sites More sharing options...
m&mv80 Posted April 14, 2009 Author Share Posted April 14, 2009 ok so looking like a transfer box swap is the best option then, what vehicles did they fit the 1.6 and 1.4 boxs into? and will they fit onto my lt85? also you are correct about the 4 pin diff and stronger half shafts but i changed the rear axle for a rangerover disc brake axle and had such a good offer for the 4 pin and shafts i couldnt say no, so i just brought a detroit locker and use standard 10 spline shafts, neither of which have broken since fitting the 35s it has su carbs so i guess it must be the 135hp version then, like i said the motor is sweet and running ok and it has been very well looked after although i am also aware of the camshafts rounding off, megajolt on the way to so that should help a bit to, thanks again Quote Link to comment Share on other sites More sharing options...
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