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should i consider an over drive transmission or is there another option?

acebooncoon

acebooncoon

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I recently put 4.10 gears in the Blazer. previous gears were 3.08. I am running 35 x15 tires. the truck seems like it is giving all its got to go 65. I do not have an rpm gauge but it sounds like its giving all its got. The last shift point I hear is when my speedo reads 50. By my calculations in truth I am going 40mph at this point. when my speedo reads 60 to 65 it seems to be wound up tight almost like it needs to shift one more time and it would be ok.

Is there an adjustment that I should have done to the shift points or is this what is correct and I need an over drive if i want to use the interstate?
 
If you have not changed the speedometer gear,the larger than stock tires will make it read slow--you may well be going 75 mph when the speedometer says 65...you should be able to cruise at 65 mph with 4:10 gears and tires that large,I have had several pickups with 4:10 gears and stock tires under 30" tall and they would rev about 2500-2800 rpms at 65 mph..
 
diesel4me said:
If you have not changed the speedometer gear,the larger than stock tires will make it read slow--you may well be going 75 mph when the speedometer says 65...you should be able to cruise at 65 mph with 4:10 gears and tires that large,I have had several pickups with 4:10 gears and stock tires under 30" tall and they would rev about 2500-2800 rpms at 65 mph..
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I don't feel like I"m running 75. I did not change the speedometer gear. I felt the truck was running slower than the speedometer was showing. Plus traffic was loading up behind me. Thats something I never have been guilty of.
 
sweetk30 said:
http://www.grimmjeeper.com/gears.html

3.08/35"tires = 2187 rpm @ 70 mph

4.10/35"tire = 2911 rpm @ 70 mph

get your self a tach and see just what your turning rpm wise . for a not to big but good tach i like this guy as he can clamp on the column and not stick out like a huge can on the dash . https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=auto+gauge+2306&_sop=15
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yeah i will i also am going to get a good reading on the speedometer to see my correct speed.
 
4.10's on 35's with a 3 speed isn't that bad IMO.

a 700R would help with freeway RPM's considerably.
 
700r was what i was thinking. I just happen to have a 1989 np241 that i obtained really cheap but that's time, money, drive shaft modifying, shift changing. the set up i have is not giving issues but i plan on taking long road trips. I suppose i could put the 700r and keep the 203.
 
IIRC the th350 and 700R are about the same length so you could swap those without messing with the shafts.
 
yeah i have not read a post yet that didn't speak of shaft modification. I may get the items together slowly on the cheap. I will do my homework and see what I'm dealing right now first.
 
Plus, the tail shaft sticks out another 1.75-2 inches farther on a 700R4 than it does on a th350. 2 ways to deal with that, 1 is a different tailshaft, or a spacer, both available through the good fella's at ORD
 
Justin V said:
Plus, the tail shaft sticks out another 1.75-2 inches farther on a 700R4 than it does on a th350. 2 ways to deal with that, 1 is a different tailshaft, or a spacer, both available through the good fella's at ORD
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you saying that if i choose to use the 203?
 
I had the same issue, even took it to a shop and paid to diagnose the problem. After that my wife pointed out it was in low range instead of high. Part time/full time isn't an issue, just double check which gear it's in.
 
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