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MQ wagon 4speed to 5speed conversions
MQ wagon 4speed to 5speed conversions
Gday guys the name Tim i have a mq wagon with a 351 clevo and a 4speed mq box it has 4.6 gears and at 100km she sits on about 3000rpm which isnt that fuel efficent, i want to get it down to 2300rpm or lower. does anyone have any ideas? i was thinking maybe a 5speed and 35's but im open to sugestions?
1982 MQ LWB 351 clev 600vac2nd Holley mild cam raised comp 4speed 2"toughdog spring+shocks 2"bodylift 33"Muds 2 240blitz lightforce + 2 IPF 86L Gas 80L Petrol boxing kangeroo Flag
1) Increasing tyre dia from 33" to 35" would give a reduction of 33/35 = 0.94
2) Change diff ratios. MQs came with 3.9, 4.111, 4.375, 4.625. 4.875. Changing from 4.625 to 3.9 would give a reduction in rpm of 3.9/4.6 = 0.85
3) Changing to a 5 speed box would change your top gear from 1.000 to 0.825 a reduction of 0.825
So to get to 2000rpm you will need a combination of 2 or more of the above. My P40 with 5 speed box, 32" road tyres, 4.375 diffs does 2000rpm at 100kph.
Pity you aren't this side of the Tasman or I would swap my original 3.9 diffs for your 4.6's.
Cheers
David
2) Change diff ratios. MQs came with 3.9, 4.111, 4.375, 4.625. 4.875. Changing from 4.625 to 3.9 would give a reduction in rpm of 3.9/4.6 = 0.85
3) Changing to a 5 speed box would change your top gear from 1.000 to 0.825 a reduction of 0.825
So to get to 2000rpm you will need a combination of 2 or more of the above. My P40 with 5 speed box, 32" road tyres, 4.375 diffs does 2000rpm at 100kph.
Pity you aren't this side of the Tasman or I would swap my original 3.9 diffs for your 4.6's.
Cheers
David
1982 Patrol K160 SWB (MQ) 4L P40 Petrol with Megasquirt fuel injection and EDIS ignition. Warn 8274 winch with Gigglepin head
its a dam shame that would perfect, what kind of acceleration difference will i see from 4.6 to 4.1or4.3? how much more will i get out of each gear?
1982 MQ LWB 351 clev 600vac2nd Holley mild cam raised comp 4speed 2"toughdog spring+shocks 2"bodylift 33"Muds 2 240blitz lightforce + 2 IPF 86L Gas 80L Petrol boxing kangeroo Flag
Not sure how to answer your question, but here are some of my general thoughts on ratios.
Max acceleration comes in at max torque which on my P40 is 2000 rpm so I was looking to have my cruising speed at 5 Hi around this figure. At the other end of the scale I wanted max torque in 2 Lo at around 10-15 kph for good offroad pulling. I also wanted my 1 Lo to be a crawler. I reckon that at idle in 1 lo you should be able to get out of the cab and walk alongside with the truck ambling along beside you like a horse
!!!
These requirements cannot all be met, at least not without changes to the transfer ratio which is not simple with the MQ transfer box.
To get the overall ratio you multiply gear ratio x transfer ratio x diff ratio. If you go to bigger tyres than the original you have to multiply further x (Original tyre dia/new tyre dia)
To get my 1 lo crawl requires an overall ratio around 40 and preferably higher. My original spec with 4 sp. box and 3.9 diffs was only 30 so I had to use 1st gear often when I really wanted to use 2nd.
To sort out my ratios I first built a spreadsheet which gave me the ratios for any combination of gearbox, transfer, diff and tyres. I then took the truck for a drive and recorded kpm and rpm through the hi gears and plotted these on a graph. Over these base (original spec) curves I then plotted the effect of various combinations of gearbox and diffs for each gear (rpm v kph). As my original setup was high geared I was looking to move the curves to the left to improve my lo ratio performance but not so far that my highway cruising performance was lowered. To maintain highway economy I introduced the 5 speed box and aimed to keep my 5th gear plot just to the right of my original 4sp box 4th gear (top) plot. I hope that all makes sense but it is a bit hard to describe.
There is one other factor to take into account when calculating kpm from theoretical ratios - tyre slippage. You should be able to get an indication of this from the tyre manufacturer's website. e.g BFG state 650 revs/mile for 235/85 at 45mph i.e speed reduction of 3.1%at 74kph
Confused? Actually it all worked out pretty much as predicted when I changed to 5 sp box and 4.3 diff. However I find with my 34" dia Simex mud tyres that once again my ratios are slightly too high in lo range 2nd, so I am looking for 4.6 or 4.8 diffs which will adversely affect my cruising performance unless I go to bigger road tyres. Here we go again!!!
However, to help with your original point here are the ratios for the 5 speed boxes fitted to the MQ, there were actually 2 types - 3.897, 2.370, 1.440, 1.000, 0.825; 4.267 (rev) or 4.222, 2.370, 1.440, 1.000, 4.622 (rev). I don't know which model had which box the second would give a better crawler gear. The transfer ratios are 2.2 lo and 1.0 high
Good luck,
David
Max acceleration comes in at max torque which on my P40 is 2000 rpm so I was looking to have my cruising speed at 5 Hi around this figure. At the other end of the scale I wanted max torque in 2 Lo at around 10-15 kph for good offroad pulling. I also wanted my 1 Lo to be a crawler. I reckon that at idle in 1 lo you should be able to get out of the cab and walk alongside with the truck ambling along beside you like a horse
!!!These requirements cannot all be met, at least not without changes to the transfer ratio which is not simple with the MQ transfer box.
To get the overall ratio you multiply gear ratio x transfer ratio x diff ratio. If you go to bigger tyres than the original you have to multiply further x (Original tyre dia/new tyre dia)
To get my 1 lo crawl requires an overall ratio around 40 and preferably higher. My original spec with 4 sp. box and 3.9 diffs was only 30 so I had to use 1st gear often when I really wanted to use 2nd.
To sort out my ratios I first built a spreadsheet which gave me the ratios for any combination of gearbox, transfer, diff and tyres. I then took the truck for a drive and recorded kpm and rpm through the hi gears and plotted these on a graph. Over these base (original spec) curves I then plotted the effect of various combinations of gearbox and diffs for each gear (rpm v kph). As my original setup was high geared I was looking to move the curves to the left to improve my lo ratio performance but not so far that my highway cruising performance was lowered. To maintain highway economy I introduced the 5 speed box and aimed to keep my 5th gear plot just to the right of my original 4sp box 4th gear (top) plot. I hope that all makes sense but it is a bit hard to describe.
There is one other factor to take into account when calculating kpm from theoretical ratios - tyre slippage. You should be able to get an indication of this from the tyre manufacturer's website. e.g BFG state 650 revs/mile for 235/85 at 45mph i.e speed reduction of 3.1%at 74kph
Confused? Actually it all worked out pretty much as predicted when I changed to 5 sp box and 4.3 diff. However I find with my 34" dia Simex mud tyres that once again my ratios are slightly too high in lo range 2nd, so I am looking for 4.6 or 4.8 diffs which will adversely affect my cruising performance unless I go to bigger road tyres. Here we go again!!!
However, to help with your original point here are the ratios for the 5 speed boxes fitted to the MQ, there were actually 2 types - 3.897, 2.370, 1.440, 1.000, 0.825; 4.267 (rev) or 4.222, 2.370, 1.440, 1.000, 4.622 (rev). I don't know which model had which box the second would give a better crawler gear. The transfer ratios are 2.2 lo and 1.0 high
Good luck,
David
1982 Patrol K160 SWB (MQ) 4L P40 Petrol with Megasquirt fuel injection and EDIS ignition. Warn 8274 winch with Gigglepin head
I love the 4.6 on road make my car alot more toey, i can take off from a standing start in 4th high with little clutch riding, it makes the car very easy to drive in the suburbs without constantly changing gears only prob is freeway driving i only get 180km to 210km out of 75l usable lpg. if u get a hold of some 4.6's i think u will like the change offroad u shouldn't have any probs spinning up 34's in 2nd. Thanx for the advice mate it made perfect sence
1982 MQ LWB 351 clev 600vac2nd Holley mild cam raised comp 4speed 2"toughdog spring+shocks 2"bodylift 33"Muds 2 240blitz lightforce + 2 IPF 86L Gas 80L Petrol boxing kangeroo Flag
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