hard 1-2 shift firepunk vb?

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superwagon

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Jun 1, 2013
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I just finished building my 48re with parts and vb that they use for comp 1 transmission. My only problem is the 1-2 shift is very late and hard. Under light throttle acceleration it won't upshift until about 2000rpm and it shifts very hard. if I let off the throttle sometimes it will shift but usually stays in first and decelerates. Under medium to heavy throttle it shifts pretty hard as well but more acceptable under those conditions. Checked my pressures and found 80 @ idle in gear, around 90 psi at my 1-2 light throttle shift, 130psi @ cruise, 160-170 @ 1/2 throttle locked up and 180psi @ WOT locked up. I have left messages with firepunk and lavon has not been able to get back to me. Has anybody else had a similar issue that could point me in the right direction? I don't want to drive this thing like this and break something! I like a nice positive shift but this thing jolts the whole truck just trying to drive around town every time it shifts.
 
Friend of mine just got a VB from him and has the same issue. I thought he was exaggerating the harshness until I rode in the truck. Feels "too" hard like what your describing, and feels like the shift could damage something. I don't believe he has tried to contact lavon about it though


I like to go fast
 
Did you check your TV screw? And when i went to a thicker fluid (Case HyTrans) it lowered my shift points, not just my stall.
 
Check your TV cable, the line pressure doesn't sound to high, and Lavon will get back to you as soon as he can, they have a few people gone this week.
 
PM me bud, I'm looking at 12 messages in front of yours at the moment, our call volume is unreal right now and I'm returning messages in the order they come in, along with keeping the shop running smoothly. Message me and I can converse while I'm on the phone.

Lavon
 
superwagon said:
I just finished building my 48re with parts and vb that they use for comp 1 transmission. My only problem is the 1-2 shift is very late and hard. Under light throttle acceleration it won't upshift until about 2000rpm and it shifts very hard. if I let off the throttle sometimes it will shift but usually stays in first and decelerates. Under medium to heavy throttle it shifts pretty hard as well but more acceptable under those conditions. Checked my pressures and found 80 @ idle in gear, around 90 psi at my 1-2 light throttle shift, 130psi @ cruise, 160-170 @ 1/2 throttle locked up and 180psi @ WOT locked up. I have left messages with firepunk and lavon has not been able to get back to me. Has anybody else had a similar issue that could point me in the right direction? I don't want to drive this thing like this and break something! I like a nice positive shift but this thing jolts the whole truck just trying to drive around town every time it shifts.
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Don't know about the 48RE, but my '98 47RE did this after building it. I replaced the output shaft speed sensor and that fixed it. Your 48RE may not even have one, I don't know. Just thought I'd throw that out.
 
I have replaced the output speed sensor with the build and also the range selector "neutral switch". I zip-tied the tv motor up out of the way and just retested. The light acceleration 1-2 shift seems to have dropped to 1400-1600 with a good bump to the shift still. If I really accelerate super easy and creep up until it shifts it might even be more like 1300 with a bump. All other shifts were just normal as far as firmness goes. I messaged Lavon with my results and see what he wants me to do next? The truck only has 80k miles and worked just fine before. I only was upgrading before I had problems with adding power.
 
I am the friend that Stubz616 was talking about. I have a VB from lavon. Does the same exact thing you are talking about. Buddy of mine said it was good. I thought it was rather hard. Also i have 47RE. Let me no what else you find out. Ill try the output speed sensor as BigPapa mentioned.
 
I adjusted my ttva tables down a little and it now shifts around 1500. It's still a little abrupt but livable. I might play with those adjustments a little more because it doesn't seem to down shift on deceleration in town when you would expect it to. It stays in third or fourth when making a turn rather than down shifting to second.
This transmission is way better than stock other than this 1-2 shift issue!
 
superwagon said:
It stays in third or fourth when making a turn rather than down shifting to second.
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This is also caused by the OSSS. If you've replaced it, you might check you wiring. Sure sounds like this is your issue.
 
Update!
I have been very frustrated since doing the transmission. Yesterday morning on my light throttle 1-2 shift it completely blew my 8 month old carrier bearing completely out. It was perfect a month ago when I did the tranny. Got it on the trailer and hauled it home with our 03 suburban 2500, that 8.1 is amazing! Doesn't even break a sweat with 10k lbs behind it! Changed the carrier bearing again and decided to drop the pan. Changed the filter and looked everything over for anything abnormal. Decided to install my old transducer and updated bw solenoid that I installed last summer after buying the truck. Put everything back together and went for a drive. This thing shifts great now!!! Just a nice little bump at the shifts and this is with the stock ttva settings! 1-2 is at about 1700rpm and 15mph, 2-3 by about 24mph under light throttle driving. I do not know why or how but something must have been wrong with the solenoid or transducer that came on the new valve body? I had no codes or anything so I don't really understand what the problem was but this is much more what I was expecting when I put this thing together. So thanks for the ideas and recommendations and I hope that maybe this will help somebody in the future!
 
Ive heard from a few diff trans people that sometimes the electronics are chit right out of the box, so just gotta get new ones. I got a new vb put it in and it didnt work, changed electronics and its been fine ever since
 
Gotta love electronics, always a wild card in a diagnosis. The solenoid should only control shift timing, not so much shift firmness, but I'm just glad that its working correctly. If you send back solenoid/transducer I can replace them with new spares for you to keep or refund you the cost of the two pieces.

Lavon
 
Thanks Lavon, I will see how much it's going to cost me to ship them back to you. Could you pm me how much a refund would be.
I just got back from another drive and I am loving the truck now! I was ready to sell it for what I owe on it yesterday.
 
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