What RPM @ 100km/h should I expect from an auto Bay?
ratty 63 - September 27th, 2009 at 10:49 PM
Hi all,
I finally fitted a tacho to my '78 Auto Bay Kombi (Ex-army) that I have owned for about a year and I think I have discovered why it sounds like it is
screaming at 100km/h in comparason with my Brothers '75 Manual Bay Kombi - because it is!
My Tacho shows 4000 RPM @ 100km/h, whilst my Brothers Tacho shows just below 3200 RPM at the same speed.
Now I did expect some difference between the auto and the manual, but is this too much?
Does anyone else have an auto Bay Kombi (2 liter) with stock rims and tyres that has a tacho fitted? What RPM does yours run at 100km/h?
R 
dangerous - September 28th, 2009 at 06:03 AM
Final drive ratio should be 4.09.(NG for late bay or NH code for vanagon)
Most convertors should have a little slippage,
but without factoring this in,
it should equate to 3414 rpm with around a 25" tyre....but 4000 sounds like it is an earlier trans.
Stock 091 bus trans manual trans would be: 4.03=3364rpm.
Earlier bus auto trans have a lower ratio of 4.45 and thus higher rpm,
and the later vanagon trans may be taller, but my book says the 1982 onwards still has the 4.09 ratio.
The 4.45 ratio would be 3708rpm at 100 with a 25" tyre.
Perhaps your tyre is lower diameter than 25"?
ratty 63 - September 28th, 2009 at 09:00 AM
| Quote: |
Originally
posted by dangerous
Final drive ratio should be 4.09.(NG for late bay or NH code for vanagon)
Most convertors should have a little slippage,
but without factoring this in,
it should equate to 3414 rpm with around a 25" tyre....but 4000 sounds like it is an earlier trans.
Stock 091 bus trans manual trans would be: 4.03=3364rpm.
Earlier bus auto trans have a lower ratio of 4.45 and thus higher rpm,
and the later vanagon trans may be taller, but my book says the 1982 onwards still has the 4.09 ratio.
The 4.45 ratio would be 3708rpm at 100 with a 25" tyre.
Perhaps your tyre is lower diameter than 25"?
|
Hi Dave,
Thanks for your reply - that is some interesting info.
Assuming that the Tachos are not 100% accurate it still sounds like I have an early trans in mine .... except it looks like a late trans to me (but
I'm no expert). Is it possible to fit parts from the earlier trans in a late case? Would changing the diff, perhaps from an earlier auto, cause
this sort of change in RPM?
I'm just wondering if, just like the mechanicals in the rest of the van, someone stuffed the diff or auto in the past and have done a cheap as
possible rebuild/repair to get it moving again .... or, did the Army order their vans with a different diff/auto to better suit their needs?
Stranger things have happened.
It is fitted with stock 14" rims with new light truck tyres, which, according to me (measured before coffee this morning) measure a fraction over
25".
Perhaps it is time to consider a rebuild on the auto to sort this problem out....
R