What diff gearing do I have? Need OD?

[alaskajosh]

This is a two part question and I thank you in advance for your help--

The previous owner had the diff gearing changed at the same time that he got a Robert Davis 3.0 transplant. He didn't now exactly what they were.. he said 3.8:1 (??) or 3.9:1 (??) He didn't know and I don't either.

Do either of these sound right? It's Rover in the front and Salisbury in the rear.


Now for part two:

It has the aforementioned gears in the diff, a SIII tranny, and this 3.0l engine. Right off the bat I burned up the Fairey OD.. it was dry of oil and I didn't check before driving away:mad:.
Would you think, based on this combination, that I'd even need to replace the OD? It's geared pretty high as it is, don't you think? It will see a lot of road use as I would like to travel long distance in it.

I know you're going to ask, "Well how does it drive"? I coudn't really tell ya' as it's been torn down ever since getting it home and will be for awhile as I address many issues.

Thank you very much, gents--

[Mercedesrover]

Unless he started swapping gear sets your truck either has the stock 4:70 diffs or 3:54 diffs out of a coiler and there's a pretty big difference between the two.

You won't know if you need an OD until you drive it a bit. With 3:54 gears I would probably think not, depending on the size tires you're running. With 4:70 I would think yes.

jim

[scott]

i've 4.7s in mine. run 235x85x16 tyres, have a fairy o/d. in 4th the 2.25 screems in pain about 45 or 50 mph. with the o/d i can cruise about 55. all this would be on the flats top end on a down hill or with a good tail wind 70

[BackInA88]

I have the same set up as Scott and can cruise all day at 65/70 MPH.
Engine is running at about 3000 RPM and in pretty good shape with a 8:1 head.

I only loose speed on the biggest hills on the expressway.
I think my Weber is limiting me so what?
May buy a new Zenith?:)


Steve

[alaskajosh]

Yes, I believe he did swap the gears. I spoke to Robert Davis, who transplanted the engine and the gears, and he said they were 3.8 or 3.9 he couldn't remember. I'm hoping one of those is a possible choice that one of you recognize..

Thanks you

[badvibes]

i've 4.7s in mine. run 235x85x16 tyres, have a fairy o/d. in 4th the 2.25 screems in pain about 45 or 50 mph. with the o/d i can cruise about 55. all this would be on the flats top end on a down hill or with a good tail wind 70

I don't know what Scott's talking about. He just told me that his 2A pushed his wife's LR3 all the way out to California at speeds up to 90 mph. :D I've followed him on the freeway as best I could with my truck, stock rebuild with a 1bbl Rochester, motor @ 6000 miles now and he always runs faster than I do. I just got back from the hills with a friend caravaning in his Dakota. On the flats on the highway he said I was running 60 pretty consistently. My speedometer isn't reliable at all. :o I have noticed that at 7000' and above my truck becomes an absolute slug though. So with a fresh motor I run 55-60 witout any trouble*.

Jeff

* as long as there are NO hills

[KevinNY]

GBR did indeed have a 3.9 gearset for a time.

[daveb]

3.9 diffs were used in santanas and rover p4's.

I drove robert's orginial 3.0 equipped 109 back in '96 or so and it had the 3.9's. it went quite nicely.



I'm hoping one of those is a possible choice that one of you recognize..

Thanks you

[TeriAnn]

GBR did indeed have a 3.9 gearset for a time.

I think Bill may still be offering a 3.9 & there is a 4.1 vailable.

I think the full range is: 4.75:1, 4.7:1, 4.1:1, 3.9:1 and 3.54:1