Hi
Chris,
My 3
litre Volvo Marcos has a 4 speed manual gearbox with electric overdrive and a
3.77:1 rear differential. In top gear, which has a 1:1 ratio, I'll be doing
around 2750 rpms at 60 mph. I'd have to check the Volvo workshop manual but
I'm sure high gear in the automatic has a 1:1 ratio as well. What really
concerns me is your high rev count at 60 mph. The recommended maximum revs for
the standard Volvo B30 engine is 5500. If you really are revving up to
6000, you would be experiencing significant power loss due to valve float, and
this is definitely not recommended. Somehow, I suspect that you're not really
revving that high because intuitively you'd know you're reaching the limit and,
with the car being new, I can't see you pushing it that hard. Most (if not all)
of the 3 litre Volvo powered cars originally came with the 3.77:1 rear axle and
in fact, I've only come across one other with a lower ration, and that was a
replacement from the original. It doesn't seem possible that you could have a
rear differential ratio low enough to produce the figures identified below
unless your transmission is non-standard.
However, have you considered that your rev counter could be
over-reading? Before doing anything else, I'd check that out. Get
your hands on one of those aftermarket tuning meters with a rev calibration
capability and check the accuracy of your rev counter. The Smiths rev
counter operates through induction, where the induction wire has a double loop
where it attaches at the rear. If it isn't attached correctly, it will not
read correctly. It appears to me that your rev counter could be displaying twice
the true revs.
I hope
this helps.
Regards,
Paul
Dransfield
3 litre Volvo
-----Original Message-----
From: Don Lattimer [mailto:donlattimer@...]
Sent: October 28, 2003 10:34 PM
To: MarcosManiacs@yahoogroups.com
Subject: Re: [MarcosManiacs] Gearing - Please Help!!!Chris,Do you know the final drive ratio? It's fairly easy to measure. Mark the driveshaft with chalk or paint and mark a rear tire also. Jack up the rear and rotate the rear wheel one complete turn while counting the number of times the drive shaft rotates. Mine is 3.77:1.It almost sounds like you are NOT in top gear.Michael Crews in West Virginia has the same setup as you do. 1970 3L Volvo with auto. I can give you his email address if you email me off-list.From all I can find, your car has a Ford Capri 3.2:1 rear axle. I have a letter from the factory to a customer in Michigan dated 9/14/73 stating that.Hope this helps.Don Lattimer#3m5759Willits, CA, USA----- Original Message -----From: eurocars77Sent: Tuesday, October 28, 2003 7:08 PMSubject: [MarcosManiacs] Gearing - Please Help!!!I could really use some help here,
I picked up my Marcos in the end of August and have been taking baby
steps with it since I bought it. It is a 3L Volvo powered car
equipped with a BW35 three speed automatic. I am facing an issue
with the final drive, I guess. Basically, I am running at around 60-
65 mph @ nearly 6grand on the tack in top gear! I noticed some
former posts about gearing the rear, is this the answer, if so what
parts will I need and where should I go for them? PLEASE help me out
here, my dream car is is leaving me dumbfounded!
Thanks everyone-
Chris Scafario
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