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View Full Version : Opinions: Ashcroft on an 88 and tire sizes



GrFa
03-08-2007, 03:15 PM
One of the last things my truck needs is trans/TC work. The rear wheels locked up on the highway while being towed on a dolly. I am assuming one or both is bad putting me in the market for a trans and TC. A buddy of mine decided he didn't like the Ashcroft in his truck so I bought it off him, haven't put it in yet (it was a good deal/cheaper than buying an OD).

I have been restoring an otherwise standard 71 NAS IIA 88 wagon. It has the standard top (not safari or alpine windows) so it may be considered relatively light weight.

I already purchased a set of 16" wheels and a set of 235/85 tires (31.7") before the Ashcroft was even in the picture. I was thinking about it now and figured this combination would probably be overkill for the 2.25. Most of my driving is done in the NE, not the flat lands. Has anyone used the Ashcroft with shorter tires (maybe a 29"/30")? I figured that might give a small enough reduction in weight/gear to still be usable.

Some quick calculations with thanks to TeriAnn's page.

65mph with Ashcroft 31.7" tires: 2,817 rpm
65mph with Ashcroft 30" tires: 2,977 rpm
65mph with Ashcroft 29" tires: 3,080 rpm
65mph stock TC 31.7" tires: 3,720 rpm

Another thing I have been considering is the weight of the tall 31.7" tire (a lot) and the 16" wheel combo which weighs more than a 29" tire and 15" wheel combo. Meaning there isn't just a reduction in gearing, but more weight to get (and keep) turning with the taller tires.

My truck will probably be used mostly on road/light off road for now (fresh resto, don't want to beat on it on the trails just yet). I realize the taller tires give a proper LR look and a lot more ground clearance too but I'm not too worried about it yet.

As of right now I have a set of 235/85/16 tires, a set of 16" wheels, and a set of 15" wheels so I am open to options. And using two different on/off road sets down the road. Thanks for any help.

TeriAnn
03-08-2007, 11:33 PM
A buddy of mine decided he didn't like the Ashcroft in his truck so I bought it off him, haven't put it in yet (it was a good deal/cheaper than buying an OD).


Since you already read my web page on gearing you know that an Ashcroft has a higher ratio than an overdrive and you can not pull the lever and get your series ratio back.:(

The Land Rover Ninety with 2.5L petrol engine had a 4th gear (1:1) ratio of 5.9:1 at the axle. Thats even lower than the Series 5.4:1 axle ratio in fourth gear. The Ashcroft which will give you a ratio almost identical to having a 3.54 R&P gives you an overall fourth gear axle ratio of 4.3:1. That''s an awfully tall gear for a 2.25L engine. Works great behind my 302 V8 though.:D

Have you considered a set of go kart wheels? ;) The Ashcroft kit is rugged, the Series transfer case is rugged but personally I would would be reluctant put it behind and engine of less than 140 HP.

GrFa
03-09-2007, 01:48 PM
Thanks TeriAnn, that is what my feeling was. I experienced it in his 109 with a 2.25, nothing like going 40mph in 3rd up a hill on the highway. I figured maybe the smaller tires would be enough to bring it back to something reasonable but I guess probably not. Looks like there will be an Ashcroft for sale. Let's hope for the time being that with the 32s and no overdrive the engine doesn't explode at 65mph on the highway.

jp-
03-09-2007, 04:31 PM
The rear wheels locked up on the highway while being towed on a dolly.

Timeout,

Have you looked into finding/fixing the current problem? I would definitely find and fix the current problem before just buying a new transmission. The Rover transmission is pretty straight forward, it might not be a bad idea to fix it. Also, it could be the rear diff that locked up and not the transmission.

zayante
03-10-2007, 11:01 PM
GrFa,

If you're considering selling the Ashcroft, drop me a line. I'd love to try it behind a GM conversion.

Chris

GrFa
03-11-2007, 01:29 PM
The axles/diffs/etc. are already completely rebuilt and the truck towed fine once the rear prop shaft was disconnected. I am most likely just swapping in a good used transmission. When I bought the truck it was hinted at that the transmission might be shot as another shot transmission was included "for spares". It is at a rover shop being looked at now anyways, I'm just giving the most likely scenarios. As I am anticipating the trans coming out I'm wondering what to do with the Ashcroft.