Another petrol to diesel conversion
Hi
Need a bit of help. I have started with 460GL, 280 petrol automatic. After spending a small fortune on LPG conversion. finaly installed 3l turbo diesel from an old(1992) 124 coupe. Bit of work, bit of cuting and welding, Engine works fine with 7225 auto box. My problem is with top speed. G is on 265/70 16 tyres and I am doing 50m/h at 3000revs. On low speed G is very quick, but after reaching 40m/h, nothing much hapens. My original vin:WDB46023327055952.
Been reading all the posts about boxes and don't understend to much of it.
HELP ANYBODY
Are you really sure the Auto box is working fine and you are in top gear? Count them as it changes.
Before it had a petrol...so max rpm maybe 6,000 rpm and max torque about 3,000 rpm. Being a G it was probably geared in top gear to do about 100mph at about 5,500 rpm .. and so 50mph at about 2,750 rpm with a cruise at 70 mph at 3,850 rpm. These are all guesses.. but you should have got them in your head before you started the conversion.
A diesel probably max rpm of 3,500 rpm? .. so about half the engine speed of a petrol... so it goes about half the max speed. Nothing odd about that. So your 3,000 rpm at 50mph is about right give or take some inaccuracy in speedo, rev counter and my guesses above.
http://4x4abc.com/G-Class/transmissions/getriebe.html
Differential ratios at Axles;
35/8 = 4,375 along with most 460
Transfer Case ratio
VG80 ratios are all the same for 460
So there must be high and low ratio Auto gearboxes for diesel and petrol G's
Alternative ratio changer is fitting bigger diameter tyres but that is limited to 31" without cutting and 33" with a bit of cutting but it will also reduce the already poor brake capacity.
265/70 16 = (265x0.70 x 2)/25.4 + 16" = 30.6" (less about 3-5%)
So even going up to 33" would only give you 7% more speed.
Hi
If you are using the OM 603 engine then it revs at 3800rpm when cruising at 70MPH ..with the turbo set up right you should be able to drop the revs to 3600rpm @ 70mph
These are the numbers for your VIN:
vin WDB46023327055952
type 460
body 460588 20
body_code 3
delivery_date 871019
engine 110994 22 003338
front_axle1 730300 2H 001221
order_num1 6753702701
paint1 5929
rear_axle1 741502 2K 001261
steering 765502 20 087189
transfer_case 750602 20 062950
transmission 720109 20 022514
According to that, your gearbox is the W4A018 (720.1), 4-speed auto with a 1:1 fourth gear.
Your transfer case is the VG80, with a road ratio of 1:1 as well.
Your axles are 730.300 (front) and 741.502 (rear) both with a 44:9 (4.888:1) reduction.
Your current tyres (265/70R16) have a diameter of approximately 78 cms. Length of circumference should therefore be equal to Pi times 78 cms or 2.37107 metres.
Therefore, at 3,500 rpm, your G must be cruising at exactly 63.5 mph:
3,500 x 1 (4th gear) x 1 (road ratio of transfer case) / 4.888 (differential ratio) = 0.716 wheel turns per minute
0.716 wheel turns per minute x 2.37107 metres per turn x 60 minutes = 101.87 kph
So 50 mph @ 3,000 revs sounds about right. There is nothing wrong with your gearbox.
Unfortunately, you don't have much options to increase your gearing. All 460s were fitted with the same VG80 transfer case and all 460 automatics have the same 1:1 direct fourth gear. Your differentials are already the fastest fitted to any 460.
Only two options IMO:
1) Fit 235/85R16 tyres in the 5.5x15" steelies: this would increase your gearing by 3.7% (not much)
2) I believe that the W461 was fitted with fast axles: 41:11= 3.727 and I also believe that they could be fitted to a W460... but I am NOT 100% sure. This could increase your gearing by 31% so that you could travel @ 71 mph at 3,000 rpm.
Morty to the rescue with some real data and facts rather than my guessing.
He speaks the truth so trust him.. guess the old 617 diesel in a 300GD is an odd beast as it revs quite higly for a diesel (4,000 rpm) and hence the lack of higher ratios and overdriven 5th gears in manuals.
So one option he did not cover was fitting a manual gearbox. The best one from the T1 vans has a 0.806 5th gear which would make it 20% faster.. makes 62mph at 3,000rpm. A fair bit of work to fit but no cutting/welding. I find cruising at 60mph best anyway to prevent the fuel consumption emptying my wallet any quicker!! With a 617 on those ratio I have seen 100mph.. but as said the 617 is an odd engine.
You are correct. The van gearbox is the only 5-speeder manual that I would recommend. The getrag is too weak IMO. But in any event I was assuming that he wanted to retain his automatic gearbox.
Hola Hombre, Many thanks for all data.
You are right about my original 280.I have checked numbers at my axles and they are as you got them number for number.
But that WAS original car before I started "modernisation". Now it is :1. axles as per original 280 gl petrol
2. transfer case 280gl petrol
3. engine and gearbox from 3.0 diesel from 124d first registration 1992 vin;WDB1241331B748027
Engine and gearbox are working very nice. Unfortunately Auto is only 4-speed and riches 4-th gear very quickly (great acceleration from 0mph to about 45mph) affter that there is a lot of power left but no gears to change. Engin will turn up to 4000rpm and higer but for diesel it is not to healthy. If van manual gearbox is the only solution can you check for me my (new?) engine and recomend me correct tranny?
Any help will be apreciated.
Muchas gracias
Hi Guys.
You know much more than I about G-s and Mercs. I was born and breed on "cars" like "SYRENA 101-103"two cylinder two stroke, "GAZ Pobieda"(rusian copy of some chevy, and as teenager had my hands in 1937 opel "olimpia".
My original g 280gl lost about 100 out of 150horses to meadows in a sky long time ago so I decided to transplanta diesel motor from 1992 124d. It is a turbo diesel with auto box. It has a lot of power, gets to 35-40mph alredy in 4-th gear very quickly. Goes up Harrow onThe Hill still accelerating. It drives 30mph at about 2000rpm
40mph at 2500rpm
50mph at 3000rpm
60mph at 3500rpm and after that revs to 40000, but speed increas is marginal 5mph.
I think it should go 60mph at about 2400-2500rpm and 70 at 3000, but what I know? Not much. I don't even know if my motor is 607 or 617 or something else. Vin number of the donor car is:WDB1241331B748027
If you knoe where to look pleas advice on correct or beter gearbox (auto prefered)
regards Pole
Hi Claude
you have an OM 603 engine mated to a 722-300 series gearbox according to the vin number for the car it came out of... the proper adjustment of the cable from the gearbox that is linked to the throttle linkeage beside the exhaust manifold is critical for the gear change / rev range if this is not adjusted correctly you will not get the gears properly and they will change back from top to 3rd as you press the accelerator further to the floor ......this engine as fitted to the 463 series G' without turbo revs at 3800rpm to achieve 70 mph and with turbo 3600rpm @ 7o mph
Fixwin is correct. Since the automatic gearbox from the W124 300D has also a direct 1:1 4th gear your gearing must necessarily be as per my previous post. You need a manual gearbox with overmultiplied 5th gear:
http://www.4x4abc.com/G-Class/transmissions/getriebe.html
The Getrag GL275 has a 0.813:1 5th gear which would increase your gearing by 23% (nice!) but it is somewhat weak. it is however relatively easy to find and i believe matches the OM603 engine of your truck easily.
Mercedes G1/18-5/4,7 is the gearbox fitted to some Transporter vans. Very strong, has a 0.806:1 5th gear (24% increase on current gearing), but it is sought after and thus more pricey than the other one. I think that it would fit to your current engine but i am not 100% sure.
Good luck.
has anyone ever looked at the use of a bolt on overdrive unit to increase gear ratios and of course save fuel too?
An Overdrive is too British a concept to even be considered by German engineers.
I have a similar problem to that of our esteemed colleague. My G300 diesel has the GL 76/27 K-5 (717.439) 5-speed Getrag manual gearbox with the 0.799 5th gear overdrive and it is fitted with the short axles (5,286:1).
I now want to fit the W4A028 (722.394) 4-speed auto, but this one has a direct (1:1) fourth gear. This means that I would be doing like 4,100 rpm @ 60 mph. No good.
The factory solution was to mate the fast axles (4.375:1) to the auto gearbox to compensate for the direct 4th gear. I could follow the same road and replace both differentials, but then my gearing for extreme off-road (specially downhill) would be too long.
Instead, I am going to mate the later VG150 transfer case as fitted to the G350TD and later models (750.651) to the auto gearbox , which has the same ratio in low as all others (2.16:1) but also an overdrive road ratio of 0.87:1. Thus, I can have the best of both worlds, a long road gearing for motorway travelling and a short gearing for extreme off-road.
Unfortunately, this option does not work for the 460, because there is just one version of the VG150 transfercase.
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Many thanks.
u probably right, I can crank it up to 3500rpm easily but the noise is horrendous and not much is happening regarding speed. Is doing max 60mph at 3500, bit to high for diesel in my opinion. I think I need a dfierent gearbox. I will have all the codes for engin, gearbox and axles tomorow so if anybody can advise?