lowering rpms at freeway speed
Hi all,
i know this has been covered in other threads, but no solutions seem to have been found.
i have an 83 280 ge (was a 300gd with stt 460333 27 026700)...i am planning on puttin the m117 5litre into it (have two UK donor 500s now)...
the 280ge does 3500rpm at 100kmh (65mph) with a 4.88 diff ratio and 32inch tyres. i dont like the thought of the v8 flying around at such speeds!
i am no mechanic but every option i think of seems to get shut down.
-overdrive unit seemed like a good idea; but no one makes them for our mercs (gear vendors sounded great, but emailed me and said no thanks)
-dont know of any 5 speed merc transmissions that would fit a 500
-diff swaps/customisation...in australia we arentlikely to find any other lower diffs! as for customisation, id consider it if possible and not worth more than our G. i saw another fellows post on swapping 461 diff gears in, but he couldnt find any part numbers or other info on this.
-i appreciate you could throw 35s or something silly on it, but how much would this drop the rpms? i hear this kills wheel bearings quickly...also, my hobbit like wife wouldnt appreciate the G going any higher.
if anyone has any answers, id be most grateful - the more comprehensive the better for a simpleton like me
many thanks
nathan
west australia
Because it's a 460 you don't have much option, other than increase tyre size. If it was a 463 then you could go for the g500 transfer box like on my 463 had. You have done as much as u can with the 460. She' going to be juicy doin 3500 at 65!. What are the ratios in the 5 speed merc van manual gearbox, could this be an option, steer away from the auto.
I don't know which bell housing you need to fit to the 5l but here's the link for the gearbox ratios
If your 280 is manual (?) then 4th gear is 1:1, so any later gearbox, auto or manual, I assume you'll use the gearbox from the 500 (?) will have overdrive in 5th gear which will make a big difference. For example if 5th was .8 or so, the RPM would be something like 2800.
On another note, ever seen a G in Aussie with a chevy 6.5 diesel?
Cheers Scott
Thanks Scott,
we have an 83 280ge with 4 speed auto. i will be using the 500 auto. it doesnt have an overdrive...ihave two 500 gearboxes to choose from, the 84 4 speed, and the 88 with the economy/sport mode switch which deals more with rev limiting/shifts...neither of which have an overdrive as far as im aware?
i thought because the final diff gear ratio is 4.88, it didnt matter what the gearbox ratios were as final drive is always 1:1??
those 6.5L diesels get stuck in every 2nd lancruiser and nissan patrol here...never seen it in a G - blasphemy! why would you want this when you can have 88kW of west germanys finest! haha
i saw a post by a landroer guy on a another forum who had some custom transfer case gearing (i dont know what?!) made so the ratio of high (roaduse) gear was dropped but low range not altered. a mate of mine said the Gs transfer case was not amenable to such a procedure?
thanks for input, please keep it coming
regards
nathan
Hi Nathan
5th gear (or 6th or 4th or what ever the last one is) will make a difference. I see now that your auto 4th is 1:1 (see the link in earlier posts on gearbox ratios, yours being 'old merc' W4A018?). So for example if you used the manual GL 275 711.117 which was fitted to 460's, you would have a 5th gear with .813 which is overdrive, or the later W5A330 Merc fitted to 463's but it is electronic. I'm sure these options would be better and cheaper than trying to modify transfer cases or diffs.
I was asking about the chevy V8's because I have a 1980 280 which is in surprisingly good condition but I don't like petrol, thought it would be fun to have a big V8 diesel in it, even though it is a chevy!
Cheers Scott
thanks guys,
for practicality, id stick with the auto...this is disappointing news!
i had put a few hopes into an overdrive, but no one seems to want to touch the issue. i cant imagine (with my all encompassing knowledge!) that the Gs transfer case differs significantly to any other 4wd, so why couldnt a custom adapter be made for a product like the gear vendors overdrive (they flat out said sorry, end of story).
how much does once inch of rubber reduce your rpms? i think my 32s dropped a 100 or 200 at 65mph on the old 31s? i wonder what 33s or 35s would see the engine doing?
there is a guy in the club, that has a 5 lt in his 460, with an overdrive!. he contacts me on the odd occasion. He is a fireman in east london, ill see if I can find his number.
peter,
id be really grateful if you can get some more info off your overdrive mate...no one seems to want to touch this one...as i said, i have the auto...a manual OD might not be so bad, but im lazy and dont want a manual!
regards
nathan
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thanks guys,
for practicality, id stick with the auto...this is disappointing news!
i had put a few hopes into an overdrive, but no one seems to want to touch the issue. i cant imagine (with my all encompassing knowledge!) that the Gs transfer case differs significantly to any other 4wd, so why couldnt a custom adapter be made for a product like the gear vendors overdrive (they flat out said sorry, end of story).
how much does once inch of rubber reduce your rpms? i think my 32s dropped a 100 or 200 at 65mph on the old 31s? i wonder what 33s or 35s would see the engine doing?