New Build in England....

[felixx]

nice build mate

[Transit80]

Thanks Felixx.

Chris

[Sheddie]

Hi Chris,
Question for you. What size tyres are you running on the Saab, and what did it originally have on it?
I just checked what my books said on your Saab, I see it has an over driven 4th with a fairly low diff, giving it an overall ratio the same as my Consul Capri (the green one below). They are both about the same power, and so far the majority of the towing has been with it.

[dales133]

I love that saab.
Looks like an old volvo

[Transit80]

The tyres on it at the moment are 175/65/15 on 6J rims, the originals were 155/15 on 4.5J rims. I dont know what the diff ratio is I cant find anything in me workshop manual to tell me. What does `over driven 4th with low diff` mean??, Ive never heard of that before.


Chris

[KCStudly]

I'll take a stab at it: It means that the trans output in 4th gear has more rev's than the engine, and that the transaxle differential final drive ratio is higher numerically.

This would give more low speed torque multiplication in the lower trans gears to get the car moving, but would still afford a reasonable final drive ratio when cruising.

Whereas with low gears in the diff, if the final trans gears were 1:1 the engine might have to buzz along.

Modern cars tend to have "highway gears" (lower numerically, "Taller" ratios) and higher gear counts in the trans; lower firsts and sometimes multiple overdrives in 4th and 5th, even 6th and up.

[Sheddie]

Hi Chris. The reason for my question about tyre size was that with the Rover wheels I wondered if it had geared it up at all. But as you originally had 155/15 tyres (I assume they would have been 155/80R15), and have gone to the 175/65R15 you have actually geared it down slightly which will help the towing situation. I was trying to get a comparison between the Saab and my old Consul Capri for tow - ability. They will both be about the same power, the Saab is about 200 lbs lighter. The diff ratio on the Saab is 4.88 & 4th is 0.84, overall is 4.099. Capri o/a is 4.125, so there is not a lot of difference there, but with your 175/65R15 and my 175/70R13 that will have quite an effect.

[Transit80]

Hi Frank and KC, gearboxes are ancient magic to me but what I can tell you is that since I put the Rover wheels on it the revs have gone up by the feel of things when its in top gear. This photo probably explains that, Rover wheels on the right.



Chris

[Sheddie]

Hi Frank and KC, gearboxes are ancient magic to me but what I can tell you is that since I put the Rover wheels on it the revs have gone up by the feel of things when its in top gear.
Chris

Your revs will have gone up very slightly, that is, revs at your actual ground speed, but not at what your speedo is telling you. There should be about a 20mm difference in the diameter this works out to only about a 3.5% difference in revs/mile. So when your speedo reads 60mph you are only doing about 58. Bit then speedos aren't that accurate anyway. Where the difference in pulling power between the Saab and the Capri occurs is that the tyres on the Capri are a bit over 2ins smaller in diameter.

[Transit80]

Just to let everyone know I am still around and still working on the trailer . Have fitted the inside and the cupboards to the back, just little bits and pieces to do.




[url=http:[URL=http://s241.photobucket.com/user/transit80/media/IMG_5337_zpsbwunejmz.jpg.html][/url]

Chris

[Sheddie]

Hi Chris welcome back.
That is all looking good Have you had time to get away in it for some camping?
I was actually thinking about you last night. I was watching a clip on YouTube of the "Geelong Revival Motoring Festival". and there was a Saab like your one racing.