1999 Winnebago Vectra Grand Tour - Allison 4 speed transmission question....

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LetsCook

LetsCook

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Jun 10, 2019
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Just purchased a 1999 Winnebago Vectra Grand Tour with an Allison 4 speed transmission (29K miles) from a private seller.  While driving it,  I noticed that it maintains about 3000RPM at about 60mph. Is this normal? Thanks for any help/advice!

edit by staff - changed message icon to topic solved and made subject more descriptive
 
The Allison 4-speed was offered with low-power diesels back in the mid 90's. Some of the Bounder diesels had it as well.  I thought that was no longer the case by 1999, but I guess I was mistaken.  There was a point in time when Allison could not build enough 6-speeds and some coach builders had to settle for the 4-speed instead.  As I recall, the 4 speed does have overdrive, one gear vs two on the 6-speed.
 
Interesting. His might not be going into lockup (i.e., overdrive.)

I just looked at the brochure for that model - it's on a Chevy P12 gas chassis (and the Allison 4 speed). I wonder if he can feel it going through all four gears?
 
Sorry folks, forgot to add: Its a 1999 Winnebago Vectra GT, 37ft, Class A gas engine, 7.4L Vortec V8. I'm not seeing an overdrive option, last I remember (and from previous vehicles) its a button on the gear shifter of which this rig does not have. It only has P/N/D/D3/D1. As far as feeling it go through all of the gears, I'm having a funny feeling it's not hitting 4th, But, then again, I'm not sure because it truly is the first time I've had a transmission do this, so I have no recollections to recall upon. It is definitely shifting, but hitting all gears, I can't be sure. Thanks for any help/advice you can offer! ;D
 
Lets cook.
Have you tried higher speeds?  I have a 6 speed and it won't shift into high gear, 6 ,until 68 mph.
Welcome to the forum.
 
ChasA - Actually, I haven't. I was a little gun shy about pushing it, I will give that a try. Unfortunately, it is in the shop getting some AC work done (AZ heat's a-coming!) so it'll be a day or so before I can try. I'll let you know what happens, thanks!
 
The top gear in a 4-speed automatic is almost always an overdrive, whether driver-selectable or not.  Allison has never been big on offering OD buttons - neither the Allison 3000 nor 4000 have them and they both have two OD gears.  I don't recall one on the 2000/2400 series either.
 
If you know differential gear ratio, transmission ratios and tire size you can calculate what the RPM should be.

David
2017 SunStar 30T
 
Thank you Gary, that makes sense. I'm still new to this, so I'll have my learning curve. Always good to learn something new! ;D ;D

dwaugh10 - I will see what information I can get and look for a formula to plug the data into. Would be interesting to see what it should be, thanks for the info! ;D
 
Watch the tachometer as you accelerate and you should see the shift points. That will tell you if it is getting into 4th gear. 


That '99 Grand Tour is a BIG coach for a gas chassis of that vintage, long, heavy and a lot of frontal area (wind resistance).  I'm thinking 3000 rpms @ 60 mph may not be unreasonable. Hope you aren't expecting a good mpg!
https://winnebagoind.com/resources/brochure/1999/1999VectraGrandTour.pdf
 
Hey Gary - Yeah, not expecting hybrid type MPG's that's for sure! ;D Just was looking for something in fairly decent shape around that year/price range. Everything else we looked at had visual clues that were show stoppers (stains on the Ozite, really bad fading on the exterior, really, really bad "remodel" jobs on the interior...). This one was esthetically pleasing with what seemed to be sound mechanical behavior. I'm going to have an Allison service shop look at it to make sure all is good.
 
You should also have a full chassis service as well. Don?t forget to check the date code on the tires, regardless of how they look seven years is the safe service life.
 
I personally would NOT have a coach with a 4-speed, ever again.  Had one of those and was pleasantly shocked when I upgrade to on with a 5-speed and later a 6-speed.
 
John C - thank you for the advice. Yes, I looked for the date code, couldn't find it. As far as I know its a number after the letters DOT. Kinda strange...

Gary - What was the improvements you saw/experienced with the 5 & 6 speed tranny's over the 4? Thank you for any insight you can provide!
 
Gary - What was the improvements you saw/experienced with the 5 & 6 speed tranny's over the 4?
Click to expand...
A 4-speed simply lacked enough gear ratio choices to manage well under changing demand conditions.  It downshifted to 3rd for almost anything, e.g. dropping below about 60 mph or the slightest grade.  Rolling hills kept it in 3rd gear all the time.  On any significant grade, and I'm talking only 2%-3% rather than mountain climbing, the 4-speed dropped to 2nd gear, an abrupt shift and bringing speed down to 30 mph or so.  Any tranny needs a low 1st gear for starting movement and a high top gear (4th in this case) for highway cruising and fuel economy. That leaves only two gears for everything in-between.  A 5-speed has 3 gears choices in between, allowing it to much better match power delivery to demand, resulting in a huge improvement in performance on city streets, country roads, and grades of all types.  A 6-speed has even more flexibility, yielding smoother shifting and more optimal fuel economy. 

New owners of a 5 or 6 speed often complain that it shifts all the time, a condition they think of as "hunting" for the right gear. However, that's just the tranny doing its job, optimizing power delivery by helping the engine stay in its most efficient power band (rpms).
 
Well, brought it to my local Allison Certified Service center. All checked out, and they say that yes, in this particular case, 3000RPM is normal. Apparently, 70MPH is about the max for this particular model, of which I probably won't even tempt. While they were in there, I had them do a maintenance service (fluid/filter change) and they said all looked good, further indicating what seems to be normal operation. Thanks again to everyone for their input & insight, I learned quite a bit!
 
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