Transmission Shifting Questions

[biped]

I'm back in my CUCV after 7.5 months in shop to remove rust. It seems like my truck shifted earlier, say 15 and 35 mph before but now shifts at 25 and 50 mph. I'm thinking of taking the truck to a transmission shop but thought I'd ask you guys first. It shifts okay but maybe a little hard. I replaced a U-joint earlier. I read where you can shift it manually and I'll try that to see if will shift when I want it to shift. Too bad these aren't 4-speed automatics. That's another topic.

 

[Tinstar]

Did you check vacuum lines and shift modulator?
Vacuum pump?

 

[rustystud]

Did you check vacuum lines and shift modulator?
Vacuum pump?

What he said.

 

[biped]

transmission shifting questions

I'd like to know if there is an inherent problem with leaving the transmission settings they way they are. I'm getting used to shifting at 25 and 50. It seems the truck runs smoother at 65 and 70 mph than it did with the 15 and 30 mph shifts. 30% of my driving is on ranch roads. That's 20mph. The rest is paved roads with highway speed limits. So what am I giving up? I'd guess fuel mileage would be poorer. Anything else, like U-joints or damage to transmission?

Are the government factory settings 15 and 30? I'm thinking they were because convoy speeds of 45 mph were the norm.

This is a great site. CUCV is a great truck.

Biped

 

[rustystud]

The higher the shift speed the more modulator and line pressure your dealing with. This in turn will cause harder shifts and more stress on the driveline. Haven't you noticed the firmer shifts ? Also if your transmission is not set-up for the firmer shifts it can cause slipping of the clutches. If you want to drive on your ranch and stay in low gear then use the shift selector. That is what it is for. In fact second gear holds stronger in manual 2nd then in automatic mode since the band is also applied.

 

[CUCVLOVER]

I bet the the vacuum lines are I need of replacement. Same thing happened to a friend's blazer. The vacume lines where all rotted and leaking causing higher shifts and such. Replace the rubber and report back

 

[ralbelt]

My M1008 shifted hard when I first got it . I replaced all the rubber vac lines and it smoothened right out.

 

[Ordak]

My M1008 shifted hard when I first got it . I replaced all the rubber vac lines and it smoothened right out.

Like wise

 

[biped]

Replaced vacuum lines. I didn't have one part, it was the connector that goes to the transmission vacuum vale assembly. Not available from AutoZone. I reused the cracked one I have. Even with that flaw, the shifting is not 20 and 40. A big improvement. I'll keep after it till I get that part. Thanks to everybody for the assistance.

Biped

 

[rustystud]

Replaced vacuum lines. I didn't have one part, it was the connector that goes to the transmission vacuum vale assembly. Not available from AutoZone. I reused the cracked one I have. Even with that flaw, the shifting is not 20 and 40. A big improvement. I'll keep after it till I get that part. Thanks to everybody for the assistance.

Biped

The modulator is a very important valve in shifting. In fact it and the governor valve basically control all shifting. As a prank in Tech school we used to punch holes in others vacuum lines and adjusted the modulator unit to mess up there transmission shifts. A couple of guys actually destroyed a TH400 by doing this. The poor kid had not gone through transmission class yet so he didn't know what was going on. I never did anything like that though ! I just rewired the ignition wires so it sounded like the engine was 180 out. What can I say, I was young and a little putz ! My favorite trick was taking the coil wire and swapping it with the number 1 wire. That way every time it cranked it would fire on number 1 so they thought they had spark and they would continue cranking over the engine until the battery was dead. I know I was a "PUTZ" !!!

 

[biped]

Hey, what about that part

Yes, Rusty, you've been bad but what about that part I need that takes the two vacuum lines and "nicely" fits them into the transmission vacuum valve assembly. If I have to fabricate something, I know it will require hard thinking and not look so nice. I'd really like to replace that part with another like it but RockAuto nor anyone else seems to have one. Biped

 

[snowtrac nome]

vacuum lines also the tps on the side of the injection pump was prone to leaking also ck the line on the vacuum pump at the back of the engine make certain it is working

 

[cpf240]

Yes, Rusty, you've been bad but what about that part I need that takes the two vacuum lines and "nicely" fits them into the transmission vacuum valve assembly. If I have to fabricate something, I know it will require hard thinking and not look so nice. I'd really like to replace that part with another like it but RockAuto nor anyone else seems to have one. Biped

If your are talking about that little rubber piece that goes between the valve on the IP and the vacuum lines, it is NLA. It is also not needed, just connect the lines directly to the valve, and remember Top to Transmission...

 

[rustystud]

Yes, Rusty, you've been bad but what about that part I need that takes the two vacuum lines and "nicely" fits them into the transmission vacuum valve assembly. If I have to fabricate something, I know it will require hard thinking and not look so nice. I'd really like to replace that part with another like it but RockAuto nor anyone else seems to have one. Biped

What "cpf240" said.